Thc vt c hoa Nguyn Ngha ThnNXB i hc quc gia H Ni 2006, 151 Tr. T kho: Loi, s hnh thnh loi, chn lc t nhin, lai to, th a bi, t pht sinh, tin ha, h thng sinh gii, chin lc tin ha, thch ng, phn chia sinh gii, tin ha khng ng u, thu mu, p mu, cy kh, x l mu, phng mu. Ti liu trong Th vin in t H Khoa hc T nhin c th c s dng cho mc ch hc tp v nghin cu c nhn. Nghim cm mi hnh thc sao chp, in n phc v cc mc ch khc nu khng c s chp thun ca nh xut bn v tc gi.

Mc lcChng 1 Gii thiu v Phn loi v h thng hc thc vt ................................................. 8 1.1 nh ngha................................................................................................................... 8 1.2 Mc tiu ...................................................................................................................... 8 1.3 Nhim v ca nghin cu cy c hoa.......................................................................... 9 1.4 Gi tr ca thc vt C hoa........................................................................................ 10 1.4.1 Gi tr trc tip ............................................................................................ 10 1.4.2 Gi tr gin tip ca a dng sinh vt .......................................................... 12 1.4.3 Gi tr la chn cho tng lai...................................................................... 13 Chng 2 Lch s pht trin ca Phn loi hc thc vt c hoa ........................................ 15 2.1 Thi tin s ............................................................................................................... 15 2.2 Nn vn minh s khai ca Ty u ............................................................................ 15 2.2.1 Theophrastus (370 - 285 trc Cng nguyn)............................................. 15 2.2.2 Caius Plinius Secundus (Pliny the Elder) (23 - 79 sau cng nguyn) ......... 15 2.2.3 Pedanios Dioscorides (Th k th nht sau cng nguyn).......................... 16 2.3 Thi Trung c............................................................................................................ 16 2.3.1 Thc vt hc o Hi .................................................................................. 16 2.3.2 Albertus Magnus, (Bc s tng hp) (1193 - 1280)..................................... 16 2.3.3 Nhng nh nghin cu thc vt c........................................................... 16

2.3.4 Thc vt cc nc hay nn vn minh khc .............................................. 17 2.4 S chuyn tip ca nhng nm 1600 ........................................................................ 17 2.4.1 Andrea Caesalpino (1519 - 1603)................................................................ 17 2.4.2 Caspar Bauhin (1560 - 1624) ...................................................................... 18 2.4.3 John Ray (1627 - 1705) ............................................................................... 18 2.4.4 Joseph Pitton de Tournefort (1656 - 1708).................................................. 18 2.5 Carl Linnaeus (1707 - 1778) v thi k Linnaeus..................................................... 18 2.6 Cc h thng t nhin................................................................................................ 20 2.6.1 Michel Adanson (1727 - 1806).................................................................... 20 2.6.2 J.B.P. de Lamarck (1744 - 1829)................................................................. 20 2.6.4 Gia nh De Candolle .................................................................................. 21 2.6.5 George Bentham (1800 - 1884) v Joseph Dalton Hooker (1817 - 1911)... 21 2.7 nh hng ca l thuyt tin ha acUyn i vi h thng hc ............................. 22 2.8 Cc h thng pht sinh chng loi chuyn tip ......................................................... 22 2.8.1 August Wilhelm Eichler (1839 - 1887) ....................................................... 22 2.8.2 Adolf Engler (1844 - 1930) v Karl Prantl (1844 - 1839)........................... 23 2.9 Cc h thng pht sinh chng loi ............................................................................ 23 2.9.1 Charles E Bessey (1845 - 1915) (Hnh 2.4)................................................. 24 2.9.2 John Hutchinson (1884 - 1972) ................................................................... 24 2.10 Cc h thng phn loi hin i............................................................................. 24 Chng 3 Loi v s hnh thnh loi .................................................................................... 25 3.1 Loi l g* ................................................................................................................. 25 3.2 S hnh thnh loi lin quan vi bin i v tin ha ............................................... 27 3.2.1 Ngun bin i ............................................................................................ 27 3.2.2 Chn lc t nhin ........................................................................................ 30 3.2.3 S bin i trong qun th v s phn ha ni ging ................................. 30 3.3 S hnh thnh loi v s tch bit ............................................................................. 35 3.3.1 S tch bit v sinh sn ............................................................................... 35 3.3.2 S tch bit v sinh thi............................................................................... 36 3.4 S hnh thnh loi ..................................................................................................... 37 3.4.1 Lai to.......................................................................................................... 38 3.4.2 Th a bi.................................................................................................... 40 3.4.3 T pht sinh................................................................................................. 40 Chng 4 Tin ha v h thng sinh gii.............................................................................. 42 4.1 Quan nim v qu trnh tin ha ............................................................................... 42 4.2 CC DNG CHIN LC TIN HA THCH NG .......................................... 43 4.2.1 Tin ha tin b (Agrogensis) ..................................................................... 44 4.2.2 Tin ha chuyn ha (Telogenesis) ............................................................. 45 4.2.3 Tin ha thoi ha (Katagenesis) ................................................................ 45 4.3 HIN TNG TIN HA KHNG NG U (HETEROBATHMY)............. 46 4.4 S PHN CHIA SINH GII ................................................................................... 47 Chng 5 Nhng nguyn tc trong phn loi....................................................................... 55 5.1 CC BC PHN LOI V TN TI TRT T CA CHNG............................ 55 5.2 CCH GI TN....................................................................................................... 55

5.2.1 Cc nguyn tc chung.................................................................................. 56 5.2.2 Nguyn tc cng b tn gi ......................................................................... 57 5.3 CC LOI MU CHUN (TYPUS) TN GI ..................................................... 58 5.3.1 Mu chun tn gi (typus)........................................................................... 58 5.3.2 Mu chun tn gi ca loi v cc taxn trong loi .................................... 58 5.3.3 Cc loi mu chun ..................................................................................... 58 5.4 NGUYN TC U TIN........................................................................................ 59 5.4.1 p dng nguyn tc u tin khi taxn b chia nh ...................................... 59 5.4.2 p dng nguyn tc u tin khi taxn chuyn v tr.................................... 60 5.4.3 p dng nguyn tc u tin khi lin kt cc taxn...................................... 60 5.4.4 p dng nguyn tc u tin khi thay i bc taxn .................................... 61 5.5 BI B TN GI .................................................................................................... 61 5.6 TN GI CA CC TAXN ................................................................................. 62 5.6.1 Tn gi cc taxn trn bc chi..................................................................... 62 5.6.2 Tn chi v cc phn hng ca n................................................................. 62 5.6.3 Tn loi........................................................................................................ 63 5.6.4 Tn gi ca taxn di bc loi .................................................................. 63 5.7 TRCH DN TN TC GI V CC TI LIU KM THEO TN GI ........... 64 5.7.1 Trch dn tn tc gi .................................................................................... 64 5.7.2 Mt s ch dn cn thit cho vic trch dn tn tc gi................................ 64 5.8 LUT CHNH T V TN GI V DU VN PHM V TN CHI................ 65 5.8.1 Lut chnh t v tn gi v cc tnh ng...................................................... 65 5.8.2 Ging vn phm ca tn chi cn xc nh bng cch .................................. 65 5.8.3 Cch vit tn tc gi .................................................................................... 65 5.8.4 Cch ghi ti liu tham kho km theo tn gi ............................................. 66 Chng 6 Ngun cc bng chng phn loi ......................................................................... 68 6.1 Hnh thi hc ............................................................................................................. 68 6.2 Gii phu so snh ...................................................................................................... 69 6.3 Phi hc..................................................................................................................... 72 6.4 T bo hc ................................................................................................................. 72 6.5 Ht phn (hnh 6.3, 7.10 7.12)................................................................................ 73 6.6 C thc vt (hnh 6.5) ............................................................................................... 73 6.7 Ha phn loi ............................................................................................................ 74 6.8 Min dch .................................................................................................................. 75 6.9 Bng chng sinh thi................................................................................................. 76 6.10 Bng chng sinh l - sinh ha hc......................................................................... 76 6.11 a l sinh vt........................................................................................................ 76 Chng 7 Cc phng php phn loi.................................................................................. 78 7.1 Phng php phn loi hnh thi............................................................................... 78 7.2 Phng php phn loi gii phu .............................................................................. 78 7.2.1 Nghin cu cu trc biu b l..................................................................... 78 7.2.2 Nghin cu cu to gii phu g ................................................................. 78 7.3 Phng php phn loi bo t phn hoa ................................................................... 83 7.4 Phng php nghin cu t bo ................................................................................ 85

7.4.1 i tng v phng php nghin cu ....................................................... 85 7.4.2 Hnh thi th nhim sc ............................................................................... 90 7.4.3 Kiu nhn .................................................................................................... 92 7.5 Phng php phn loi izoenzym ............................................................................. 93 7.5.1 nh ngha izoenzym................................................................................... 93 7.5.2 Phng php phn tch izozym bng k thut in di................................. 94 7.6 Phng php phn loi bng ADN ........................................................................... 97 7.6.1 K thut phn ng trng hp - PCR............................................................ 97 7.6.2 Phn loi da trn k thut ct gii hn - RFLP ......................................... 98 7.6.3 Phn loi da trn k thut nhn ngu nhin ADN a hnh - RAPD .......... 98 7.6.4 Phn loi da trn k thut nhn on AFLP.............................................. 99 7.6.5 Phn loi da trn k thut tiu v tinh l cc on ADN ngn c mt s lng cc chui nucleotid lp li - SSR ....................................................... 99 Chng 8 Ngun gc v phn loi Cy C hoa (Anthophyta) hay cy Ht kn (Angiospermae)...................................................................................................... 101 8.1 Ho thch, thi gian xut hin v a dng ha ca thc vt C hoa....................... 102 8.2 T tin thc vt C hoa ........................................................................................... 103 8.3 Cc cy c hoa u tin........................................................................................... 104 8.4 Mi quan h ca cy c hoa vi ng vt (Hnh 8.5) ............................................. 106 8.4.1 S th phn................................................................................................ 106 8.4.2 S pht tn ht ........................................................................................... 107 8.4.3 ng tin ha v sinh ha ......................................................................... 107 8.5 Trung tm ngun gc cy c hoa v con ng di c ca chng .......................... 108 8.5.1 Trung tm ngun gc vng cc.............................................................. 108 8.5.2 Trung tm ngun gc ng Nam ........................................................... 109 8.6 Trung tm bo tn hay l trung tm di c ............................................................... 111 8.7 Tin ha sinh thi ca Thc vt C hoa.................................................................. 112 8.8 H thng phn loi Cy C hoa .............................................................................. 114 8.9 Cc c trng ca cc phn lp............................................................................... 122 8.9.1 Lp Hai l mm - Dicotyledoneae = lp Mc lan - Magnoliopsida.......... 122 8.9.2 Lp Mt l mm - Monocotyledoneae = Loa kn - Liliopsida ................. 123 Chng 9 Xy dng v qun l phng mu cy kh (Herbarium) .................................. 125 9.1 THU MU V P MU........................................................................................ 125 9.2 CCH X L ........................................................................................................ 126 9.3 XC NH TN KHOA HC............................................................................... 128 9.4 QUN L MU CY KH.................................................................................. 129 9.5 CHC NNG PHNG MU CY KH............................................................. 130 9.5.1. Nhn .......................................................................................................... 132 9.5.2. Trnh by mu ........................................................................................... 133 9.5.3. Sp xp mu .............................................................................................. 134 9.5.4. Dit cn trng ............................................................................................ 134 9.5.5. Mu chun ................................................................................................. 136 9.5.6. Trao i mu ............................................................................................. 136 Chng 10 Phng php xc nh tn cy ......................................................................... 137

10.1 10.2 10.3 10.4 10.5 10.6

Cc thut ng hnh thi hc ................................................................................. 137 Phn loi cc mu cy ......................................................................................... 137 Phn tch trc khi xc nh ................................................................................ 146 S dng kha phn loi................................................................................... 147 M t.................................................................................................................... 148 Lp kha xc nh................................................................................................ 149

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Li ni uThc vt C hoa (Anthophyta) hay cn gi l Thc vt ht kn (Angiospermae) l mt trong nhng nhm sinh vt a dng nht, ph bin nht, bao ph khp b mt Tri t, t vng xch o n cc cc, t vng ma m n vng kh hn. N cng l mt trong nhng nhm sinh vt c ch nht v c ngha quyt nh s sng cn ca Tri t. V vy, vic tm hiu n mt cch chi tit c ngha v cng quan trng. Vit Nam l di t cui cng ca dy Himalaya, nm trn b bin pha Ty ca Thi Bnh Dng gia hai i lc c Gondvana v Laurasia cho nn h thc vt Vit Nam kh a dng, c nhiu nt c bit. Do tri qua mt thi gian di nhn dn ta phi tin hnh cuc chin tranh thn thnh v i gii phng t nc cho nn vic nghin cu h thc vt ni chung v thc vt C hoa ni ring cha nhiu, cha c tnh h thng, nhiu loi v thm ch nhiu chi v h cn b st, cha c m t. Nhng kt qu nghin cu trong nhng nm gn y ca nhiu nh thc vt trong nc cng nh quc t chng minh iu . Bc sang thin nin k mi, thin nin k i mi v pht trin ca t nc, vic nghin cu h thc vt ni chung v thc vt C hoa ni ring bc sang mt giai on mi. V vy, gp phn cho cng tc nghin cu thc vt C hoa trong giai on mi, chng ti cho ra mt cun Thc vt C hoa nhm cc mc ch sau: Gii thiu nhng thng tin mi nht v cc h thng phn loi thc vt C hoa. Gii thiu nhng phng php tip cn mi nhm gip cho cc nh thc vt ha nhp vi th gii bn ngoi. Cung cp nhng thng tin mi v cc h thc vt C hoa, c bit l nhng du hiu nhn bit lm c s cho vic nhn dng nhanh nht, phc v cho nhu cu ngy cng tng ca x hi, nht l trong cng tc nh gi, bo tn, s dng mt cch hp l v pht trin bn vng ngun ti nguyn a dng sinh hc ca h thc vt Vit Nam. Do thi gian hn ch v thiu nhiu t liu cp nht nn cun sch khng trnh khi nhng sai st, rt mong c s ng gp ca bn c gn xa. Tc gi

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Chng 1 Gii thiu v Phn loi v h thng hc thc vtNi n phn loi thc vt ch yu ni n thc vt c hoa bi y l nhm sinh vt v nhm thc vt ni chung thnh hnh trn tri t, l nhm sinh vt c ngha quyt nh s sng cn ca cc sinh vt khc trn hnh tinh chng ta trong c con ngi. Xut pht t nhm thc vt c hoa, t rt lu con ngi quan tm n chng, s dng chng cho cuc sng k t thi nguyn thy s khai v t buc con ngi tm cch nhn dng chng, t tn cho chng trao i gia tc ngi ny vi tc ngi khc. Khi khoa hc tin b cc nh nghin cu trn c s nhng kinh nghim ca cc tc ngi khc nhau tm cch tip cn vi thin nhin v dn dn khoa hc phn loi thc vt ra i m trc ht l cy c hoa hay cn gi l cy Ht kn ...

1.1

nh ngha

Phn loi thc vt l mt lnh vc rng ln lin quan n vic nghin cu a dng thc vt v vic xc nh, t tn, phn loi v xem xt mc tin ha ca thc vt. Phn loi thc vt l sp xp cc cy thnh nhm c cng tnh cht chung, t tn cho chng v sau sp xp cc nhm thnh h thng theo mt trt t nht nh. Cc loi tng t ca cy c hoa c trong cng mt chi, cc chi ging nhau trong mt h. Cc h c cc tnh cht chung gp thnh mt b, cc b gp thnh lp v cc lp thnh cc ngnh. Phn loi thc vt l sp xp cy theo mt trt t cc th bc nh l loi, chi, h... trn c s cc c im chung, xy dng mi quan h ln nhau. c gi l h thng hc thc vt c hoa. Trc y, phn loi hc ch dng li ch nhn dng v sau sp xp chng thnh nhng bc taxn khc nhau m khng h cp n vn huyt thng. Trong qu trnh pht trin phn loi hc khng ch dng ti m tin su v xem xt huyt thng v khi phn loi hc v h thng hc c chung mt ngha nh nhau. nh loi l nhn bit mt s tnh cht ca hoa, l, qu, thn v gn cho cy mt ci tn. Nhn bit xut hin khi quan st mu c mt s tnh cht ging nhng cy bit trc y. Khi so snh mu vi cc loi tng t m thy rng n khc vi mu ca cc loi th khi c th coi mu em so l loi mi. Taxn l mt thut ng ch vi bt k nhm phn loi ca bt k bc no nh loi, chi, h. Tn gi l s biu hin theo mt trt t cc tn ca taxn ty theo lut gi tn thc vt quc t. Lut cung cp quy trnh la chn tn ng v cho tn mi. M t l thng k cc tnh cht ca cy. Mi tn cy phi km theo mt bn m t. Thut ng h thc vt dng cho nhng cy mc trong mt vng a l ring bit c lit k theo th t hoc nhng bng m t nhng cy vng .

1.2

Mc tiuPhn loi thc vt c bn mc tiu: Thng k thc vt ca th gii; Cung cp phng php xc nh v thng tin; To ra h thng phn loi tng hp;

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Chng minh s tin ha ca a dng sinh vt. Mc d thng k h thc vt th gii hon thnh cc vng n i Bc bn cu, nhng cn nhiu h thc vt cn cha v cha th hon thnh trong mt thi gian ngn, nht l i vi vng nhit i. Bn cnh tn gi, phi km theo bn m t, kha xc nh, bng tra, hnh v, cc cm nang v cc cng b khc nhm gip cho vic xc nh mu vt. Cng ngh hin i l dng my tnh xc nh. Trong tng lai cc chng trnh my tnh c th c dng xc nh cy. Hin nay cc chng trnh ny mi bt u v trc ht truy nhp cc ti liu tham kho nh my tnh s tit kim nhiu thi gian so vi vic lm bng tay. K t khi hc thuyt ac Uyn ra i, cc nh sinh hc c th chng minh rng cc mt xch tin ha xut hin trong cc taxn. S pht trin hay cc mt xch tin ha ca mt taxn l s pht sinh chng loi ch ra rng a dng loi v cc mt xch tn ti khng xy ra t pht m c th c mt dng t tin. Phn loi hin i c gng s dng cc thng tin v cy xy dng cy pht sinh chng loi. T khi cc thng tin v ha thch l t cng b, c bit i vi cy c hoa, nhng thng tin phi c tp hp to ra cc gi thuyt lin quan ti tin ha.

1.3

Nhim v ca nghin cu cy c hoa

Nhim v c bn ca nghin cu thc vt c hoa trc ht phi phn loi, nghin cu cc mi quan h tin ha gia cc taxn v l c s tip tc nghin cu gi tr ca chng phc v cho cuc sng ca con ngi. H thng hc cy c hoa khng ch l mt khoa hc thun tu m t, lp cc danh mc m l mt mn tng hp ca nhiu s kin sinh hc khc nhau, i khi tng chng nh khng c ngha t phn t n c th, qun th v h sinh thi, xc nh hng tin ha ca chng. Tuy nhin, vic nghin cu h thng hc cn lu mi c th kt thc bi s phong ph v a hnh ca chng. V th, hin nay cc nc nhit i, hng nm khng ch c hng trm loi mi m c hng chc chi mi, thm ch c h mi, v d nh Vit Nam ch my nm gn y pht hin v m t mt s chi mi v hng trm loi mi. Nhim v tip theo l xc nh mi quan h huyt thng gia cc bc taxn. Ngi ta gi n va l nn tng v khng c n th cc lnh vc khoa hc khc lin quan n cy c hoa s tr nn qu qut, phin din, ng thi n l khu kt ni cui cng ca cc khoa hc khc v thc vt c hoa. Nghin cu h thng hc cy c hoa ngy cng c ngha ln trong vic s dng ti nguyn mun hnh mun v ca chng (s gii thiu mc 1.4). tin hnh nghin cu h thng hc cy c hoa, ngoi nhng phng php hnh thi hay ni cch khc, phng php phentp, hin nay ngi ta quan tm nhiu ti phng php tip cn mi phng php gentp t mc gin tip (kiu nhn), mc cn trc tip (izoenzyme) n trc tip nh trnh t sp xp ca ADN. Khoa hc h thng cng php trin, cc phng php c s dng ngy cng nhiu v cng i vo bn cht ca loi. Cc phng php hin i s h tr, lm chnh xc thm v iu chnh cho nhng phng php truyn thng nhng n khng th thay th cho phng php truyn thng bi yu cu thc tin qu s ang ngy cng i hi n. Nhim v th 3 ca vic nghin cu cy c hoa hin nay l xy dng mt l thuyt khoa hc v h thng nhn thng tin. Mt s phn loi hon ho th hin hai chc nng: l thuyt khoa hc v h thng nhn thng tin. Chc nng l thuyt khoa hc gii thch, cung cp nhng bng chng c ch cho trt t nht nh ca cc bc. Nu chng ta xc nh 1 loi mi hay mt taxn bc cao hn loi th chng ta c th khng nh v tr ca n trong h thng vi cc c im chnh ca n. Chc nng h thng thng tin: v mi tn gi 1 bc taxn tng t nh nhng chic cha kha ca cc ngn ko khc nhau v ngc li, vic xy dng cc kha nh loi cho ta xc nh tn taxn ca i tng m chng ta mun. V th vic phn loi v xy dng cc kha phn loi l mt phn nhim v ca h thng hc. Nh m n lm gim gnh nng cho cc nh thc vt khc khi thu thp thng tin. Nhng thnh tu ca cc nh sinh hc khc lin quan n thc vt s khng c ngha nu nh nhng kt qu phn loi khng ng tin cy. Vic hiu bit chnh xc cc du hiu ca cc loi khc nhau v s phn b ca chng c ngha quyt nh trong sinh hc ng dng.

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1.4

Gi tr ca thc vt C hoa

Vn gi tr ca thc vt c hoa i vi con ngi l xem xt chng tr gi bao nhiu tin, hoc ng gi bao nhiu. V vy khi cp n gi tr ca thc vt c hoa ngi ta u tnh mi ci ra gi tr tin. Tuy nhin khc vi cc gi tr khc ngoi tin ra, thc vt c hoa c nhng gi tr v cng to ln m khng th nh gi bng tin c m ng hn gi tr ca chng l v gi. Bi v khng c thc vt c hoa trn Tri t ca chng ta th s khng bao gi c s sng. Khi cp ti vn ny, Mc.Neely (1988), Mc.Neely et al. (1990) chia thnh hai loi gi tr: gi tr trc tip v gi tr gin tip. Trong gi tr trc tip thuc hai phm vi tiu th mang tnh thng mi trn phm vi quc t v tiu th trong phm vi a phng. Cn gi tr gin tip bao gm nhng ci m con ngi khng th bn. Nhng li ch bao gm s lng v cht lng nc, bo v t, ti to, gio dc, nghin cu khoa hc, iu ha kh hu v cung cp nhng phng tin cho tng lai ca x hi loi ngi.

1.4.1 Gi tr trc tip1.4.1.1 L ngun cung cp lng thc v thc phm Mt trong nhng gi tr ca thc vt c hoa l cung cp thc n cho th gii. 3000 loi trong s 250.000 cy c coi l ngun thc n, 75% cht dinh dng cho con ngi do 7 loi ca La, M, Ng, Khoai ty, Mch, Khoai lang v Sn, 3 loi u cung cp hn 50% cht dinh dng cho con ngi. Mt s khc cung cp thc n cho gia sc. Trong c trn 200 loi c thun ha lm thc n, 15 - 20 loi l cy trng quan trng Poaceae v Leguminosae l hai h ln nht tip theo l Cruciferae, Rosaceae, Apiaceae, Solanaceae, Lamiaceae. Mt s h c ngha khc nh Araceae, Chenopodiaceae, Cucurbitaceae v Compositae. mc a phng ti nguyn thc vt cung cp ngun dinh dng cn thit. Pru qu 139 loi c tiu th, trong 120 loi l hoang di, 19 c ngun gc t hoang di v t trng. Ngoi cc loi khc c th n c, hng chc loi cy lng thc, thc phm mi pht hin.

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1.4.1.2

Ngun cung cp g

G l mt trong nhng hng ha quan trng trn th trng th gii chim t l ln trong cc mt hng xut khu. Nm 1959, tng cng gi tr ton cu ca g xut khu l 6 t USD phn ln ly t vng n i. Nhng nc xut khu g ln l M, Nga, Canada xut g trn, g x; M, Nga, Anh v Phn lan xut g p. Cc nc nhit i xut khu g nhiu l Malaixia, Papua-Niu Ghin, Gabon xut g trn, Malaixia v Innxia xut g x v g p. Cc nc ang pht trin vic thu nhp t g chim t l thp. Nghin cu Amazn cho thy rng loi cy g rng ma trong khu nghin cu c dng ngoi ci un (Prance et al., 1987). 1.4.1.3 Ngun cung cp song my Sau g, song my l ngun ti nguyn quan trng th 2 xut khu. Hu ht l cc loi mc hoang Nam v ng Nam . Cc nc c cng nghip song my ln l Phillipin, Trung Quc, n , Srilanca v Thi Lan. Trung tm a dng ca song my l bn o Malaixia vi 104 loi trong 38% l c hu. 1.4.1.4 Ngun cung cp cht t Cht t khng phi l nhn t quan trng i vi ph rng m hu ht cht t ly t savan, r bi, t nng nghip (Eckholm v cs., 1984; Myer, 1980). Tuy nhin v ci t ang tng nhanh v dn s ang tng. Gi tr tiu th cht t cng c th tnh s ci t dng si v un nu c ly t rng, trng cy bi. 1.4.1.5 Ngun cung cp thuc cha bnh Theo Farnswarth (1988) c ti 80% ngi dn trn th gii s dng thuc truyn thng. Khong 119 cht ha hc tinh khit ly t 90 loi thc vt c hoa khc nhau c dng lm thuc trn ton th gii. Mt s trong cung cp c s cho 24 - 25% tt c v thuc sn xut trong nh my M trong 20 nm qua. Trn 40% n thuc M da vo ngun thin nhin. phm vi a phng cy thuc c s dng rt rng ri. Ngi ta thng k trn 21.000 tn cy c thng bo l lm thuc trn phm vi ton th gii trong khong 5.000 loi thc vt c hoa c nghin cu ton din nh l ngun tim nng ca thuc mi. Trn 80% dn s cc nc ang pht trin sng da ch yu vo cc cy thuc. Cy thuc phin thu hoch t hoang di l chnh. V d, c 2/3 loi c dng lm thuc ly t hoang di. Mt s cy thuc ln c trng nh Gentiana lutea, Valeriana mexicana, Echinala arnica, ch mi bt u 20 nm nay. Mt s cy c gi tr quan trng nht trong bun bn l Papaver spp., Cinchona spp., Chamomilla recutita, Mentha piperata (Schumacher, 1991). Digitalis purpurea cho digitalin v D. laurata cho digitoxin l hai glucosit (cht kch thch) rt quan trng nh n m hng triu ngi sng st. Quinin, mt alcaloit t v Cinchona ln u tin vo nm 1820 c dng thnh cng trong cha st rt. Cht diosgenin ly t cy Dioscorea deltoidea mc chn Himalaya, thuc Bc n. 1.4.1.6 Ngun cung cp cy cnh Trong cy cnh c nhiu dng khc nhau trc ht l nhng cy ly hoa. Ni ting phi k n hoa Lili. N c trng Trung Quc vi mc ch lm cnh v lm thuc 2000 nm nay. Trong thi k Hy Lp, hoa Hng, hoa Lili, hoa Tm, Anemone c trng chu u, Anh c 3000 loi c trng ph bin v nhiu th khc nhau. Tng xut khu th gii v hoa Cc, l Cc v cy dng l 2.488 triu USD trong nm 1985. Gi tr bun bn th gii v hoa v cy t 1981-1985 trung bnh nhp hoa ct 1238,79 triu USD v nhp cy sng 915,76 triu USD, nhiu nht l c, sau l M, Php, Anh, Thy S v Thy in. Xut khu hoa ct 1101,79 triu USD nhiu nht l H Lan, tip theo l Clmbia, Ixraen v v xut cy sng 8882,15 triu USD nhiu nht l H Lan, an Mch v c. Bn cnh nhng hoa truyn thng , cc loi Phong lan l ngun cy cnh c gi tr ln c mi ng a thch v th nhiu loi ang b khai thc kit qu. n nay c trn 5.000 loi lan c CITES ghi nhn cm bun bn trn phm vi ton th gii. Khong 90% Phong lan bun bn

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l nui nhn to. Nc bun bn ln nht l Thi Lan (Dendrobium). Hai chi Paphiopedilum chu v Phramipedium ang b nguy cp cn c bo v. Nhu cu cy cnh vng kh hn ni ting l cc loi xng rng lm cnh, hng nm c khong 14 triu cy c em bn trn phm vi ton th gii. Ni nui trng nhiu nht l H Lan sn xut 18 triu cy/nm, cn M bun bn 10-15 triu cy. Mxic l mt trong nhng trung tm chnh ca s a dng ca h ny xut khu khong 50.000 chi hng nm. Cc cy mng nc khc gm cc loi Euphorbia, Pachypodium cng c bun bn trn th trng quc t. Mt trong nhng nc chnh l Madagasca hng nm xut khu khong 135000 chi tt c l t hoang di. Cui cng nhng loi c cn hnh cng c s dng lm cnh t xa xa nh Narcissus c 40 loi Ty Ban Nha v B o Nha. Nm 1987, Anh xut 87 triu d Narcissus khong 4 triu bng Anh. Mt s trong N. asturiensis v N. cyclamineus c xut sang H Lan ti xut cho ton th gii. Ngun chnh dng hoang di l Th Nh K.

1.4.2 Gi tr gin tip ca a dng sinh vt1.4.2.1 Sn phm ca h sinh thi - im khi u ca chui thc n ca h sinh thi Kh nng quang hp ca cy ni chung v cy c hoa ni ring ly nng lng mt tri to cc sn phm cho loi ngi. cng l im xut pht ca mt chui thc n khng th tnh c v t dn n nhng sn phm ca ng vt, l ngun thc n cho con ngi. Do vic ph thm thc vt c hoa bng cc cch khc nhau nh dm p qu mc, khai thc qu mc v g, t rng qu nhiu s hy dit kh nng s dng nh sng mt tri v cui cng lm mt i s sn xut sinh khi ca thc vt v mt i c x hi ng vt, k c con ngi (Likens et al., 1977). 1.4.2.2 Gi tr v mi trng a. Bo v ngun nc Cy c hoa to ra cc h sinh thi chnh trn Tri t, c vai tr quan trong trong vic bo v ngun nc cho cc sinh vt trn Tri t tn ti, hn ch l lt v hn hn. Tn l, thn cy, l kh lm gim tc ht nc ri xung t, hn ch s tc ng trc tip ln b mt t tc l ngn cn dng chy. R cy cng vi h ng vt t lm cho t ti xp, tng thng kh, tng thm ca nc cng gp phn lm gim dng chy, phn b lng nc t ngy ny qua ngy khc. Theo Daniel v Kulasingham (1974), rng trng Cao su, C da Malayxia ch gi c mt lng nc nh trong lc rng t nhin gi nc sut trong ma kh ln hn hai ln so vi rng trng. Nhng hin tng lt t ngt v khng khip Bnglaet, Philippin, Thi Lan v gn y Vit Nam l kt qu ca vic cht ph rng. b. Bo v t ai Thm cy c hoa ni ring v thm thc vt ni chung lm nhim v bo v v gi t, n lt n li l c s cho x hi sinh vt pht trin. R cy, thm mc trn mt t cng tham gia vo vic chng xi mn t. c. iu ha khng kh Cy c vai tr quan trng hn ch tc gi, lm gim nng ca cc ta nh trong ma nng v hn ch s mt nhit trong ma lnh. mc vng, s bc hi ca cy vo khng kh to ra ma. Mt rng s lm gim lng ma hng nm gy ra hin tng savan hay sa mc ha. mc ton cu, cy m bo cho chu trnh CO2. Mt rng lm cho CO2 tng ln cao v dn n tng nhit ca kh quyn. Cy cng l ngun ti to O2 m cc loi ng vt v ngi rt cn n tn ti d. Lm sch mi trng Gi tr lm sch mi trng c th hin bng cc loi ch th cho mi trng gip cho vic bo v mi trng trong sch. Nhiu loi thc vt c kh nng ht cc kim loi nng lm sch mi trng. Mt s cy sng nc nh Bo ty, Bo ci... cng c kh nng hp th kim loi c, cc ha cht c.

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1.4.2.3

Mi quan h gia cc loi

Nhiu loi cy rt cn cho con ngi. Nu cc loi b mt s nh hng ti con ngi. Mt v d cc cy trng, cn cn trng, chim th phn, v n lt mnh cn trng li cn cy ly thc n t mt hoa hay hoa qu v thm ch c nhng k sinh trng v su bnh hi cy. Nhiu loi cy ph thuc vo cc loi ng vt n qu nh chim, di pht tn ht gip chng v ngc li cc loi ng vt li cn hoa qu v ht t cc loi cy. Mt v d in hnh cc loi cy cung cp cho t cht dinh dng nh cc vi khun, nm ph hy cc xc thc vt ly nng lng v thi cc mui khong vo lm cho t tt ln, l ngun thc n cho cy. Cc si nm lm tng kh nng hp th ca r cy i vi nc v mui khang cn mt s vi khun ht nit khng kh gip cho cy hp th, cui cng n lt cy li ginh mt phn thc n cho vi khun tn ti. Cy c hoa l nhng nh my ha cht c bit v mt vi ha cht ca chng c cch mng ha mt s qu trnh. V d nh Steroit t c Mexico to vin thuc to ra cc nhn t kim tra sinh hng lot 1.4.2.4 Gi tr tiu khin, gii tr S a dng ca cc loi thc vt nht l thc vt c hoa to ra nhng cnh quan khc nhau nh va c rng rm, rng tha, rng rng l, rng kh, cc loi trng khc nhau rt a dng v do to nn nhng cnh quan hp dn, nhng hnh th k d v p mt hng nm thu ht hng triu ngi i tham quan du lch sinh thi. Khi iu kin sng cng cao th nhu cu tham quan du lch sinh thi cng i hi, v vy cc cnh quan thin nhin l ht sc quan trng. V d 80% ngi Canaa, mt nm s dng 800 triu la tham gia cc on tham quan (Fillon v cs., 1985); M 100 triu ngi gi v vi con s tr con tng t i tham quan mi nm tiu 4 t la (Shaw and Mangun, 1984). Nh vy, vic du lch sinh thi tng ln mt cch cha tng thy. l gi tr ca a dng cy c hoa v nhng cnh quan do chng to ra. 1.4.2.5 Gi tr khoa hc v o to Nn cng nghip ngy cng pht trin, din tch rng ngy cng b ph hy nht l cc rng nguyn sinh m nhiu ni, nhiu nh nghin cu mun tm hiu v nghin cu cng khng cn. Nhng khu bo tn m hin nay cc quc gia ang bo v l mt ti sn khng nhng qu v ngun ti nguyn phc v trc mt, v ngun gen to ging cho cc th h mai sau, l ni bo v mi trng cc k c hiu qu v a nng m chng cn l a bn phc v cho nghin cu khoa hc tm hiu thin nhin, tm nhng b n trong n nay con ngi vn cha bit c. Cc nh vn, nh th, nh nhip nh, nh quay phim nh vo rng ni v tnh a dng cc sinh vt ca chng sng to nn nhng tc phm ngh thut bt h phc v cho nhu cu cuc sng ca con ngi ngy cng nng cao. Nhiu b phim, nhiu cun sch, nhiu chng trnh tivi da trn cc mt khc nhau ca a dang sinh vt ra i.

1.4.3 Gi tr la chn cho tng laiHin nay ngi ta ang chun b tm nhng loi phc v cho cha bnh him ngho nh ung th, HIV. Hin nay, cc loi thc vt nht l cy c hoa c cha nhiu thnh phn ha hc m cho n nay cha c pht hin. Vic nghin cu v ng dng cc thnh phn ha hc rt c trin vng trong tng lai. Thuc chng st rt c iu ch t mt s cy trong cc h Simaroubaceae, Celastraceae, Saxifragaceae, Meliaceae. Nhiu loi c nhng sn phm y hc c o, c hot tnh sinh hc cao c pht hin ngy cng nhiu. Qua phn tch cc cy Vn quc gia Cc Phng, 27 loi metanol c chit t 22 loi cy; 24 loi c hot tnh chng st rt, 4 trong s c chng minh chng c Plasmodium falciparum D6 (Chloroquine - sensitive) v W2 (Chloromine resistant) vi gi tr IC70 di 10 ig/ml trong mi trng hp. Ngoi ra, chng cn loi b mt s cc t bo c. Khi th nghim chng 14 dng t bo u ngi, cc cht chit bng metanol t l v v Ficus fistulosa th hin hot tnh chng st rt c gi tr. 13 cht chit ly t 12 loi c th kh nng chng HIV. Cht chit t Ficus glandulifera,

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Bischofia javanica, Shorea chinensis, Dracontomelum duperreanum c hot tnh sinh hc mnh. Qua phn tch cc cht chit ca thc vt t nguyn liu Vit Nam v 350 cht chit t cc ni khc trn th gii cho thy cc cht c hot tnh sinh hc cao (17%). R rng, trong cy c hoa cn cha nhiu iu b n m cha c khm ph. C th ni y l ngun ti nguyn tim n, cho n nay, t c bit n. Do , chng ta phi c trch nhim bo v cho cc th h mai sau.

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Chng 2 Lch s pht trin ca Phn loi hc thc vt c hoa2.1 Thi tin s

Con ngi bit pht hin cc loi cy n, cha bnh v t h bit s dng em trng mt s loi quan trng. Ty theo yu cu, h chn cc loi c mi v thm ngon lm rau hoc loi c sn lng cao i vi cy lng thc. Nhng nghin cu hin nay ch ra rng ngi nguyn thy cc vng xa xi ho lnh nhn bit v t nhng tn chnh xc i vi phn ln cc loi cy ni h sng. Mt s trong h lun lun dng cy ruc c, hay lm tn c, mt s khc dng lm thuc cha bnh nh cha vt thng, cm, hay gy ng... Vic phn loi ca ngi tin s t nht da trn mc ch c li hay c hi ca cy.

2.2

Nn vn minh s khai ca Ty u

Nn vn minh s khai ca Ty u pht trin trong cc vng nh Babylon v Rp, y vic trng trt bt u. T nn cng nghip gip cho nn vn minh cm nang thc vt c mt tm quan trng ln. Tuy nhin n khi ch vit pht trin v cc nguyn liu giy c lm t Ci sng Nil (Cyperus papyrus) th nhng kinh nghim v kin thc v cy c c th nhn bit mt cch d dng.

2.2.1 Theophrastus (370 - 285 trc Cng nguyn)Nh trit hc Theophrastus l hc tr ca Aristotele thng c gi l Ngi cha ca thc vt hc". Sau khi Aristotele cht (nm 323 trc Cng nguyn), Theophrastus tha hng th vin v vn ca Aristotele. Theophrastus ni ting vi hng trm bn tho nhng ch c hai bi pht biu v thc vt sng mi Enquiry into Plants v The Causes of Plants. Theophrastus phn loi cc cy thnh cy tho, cy na bi v cy g, ng m t khong 500 loi cy khc nhau, ng ch ra nhiu sai khc trong cy nh kiu trng, v tr bu v cm hoa. Tc gi phn bit cy c hoa v cy khng c hoa. ng cng nhn thy c im cu trc nh v ngoi ca qu, s tch bit cc m. Nhng thng tin v thc vt trong cc bi vit ca Theophrastus to nn ting vang ln v mang tnh trit l. Nhng ng gp u tin ca cng trnh khng thay i cho ti thi k sau thi Trung c. Nhiu tn cy hin nay bt ngun t thi Theophrastus.

2.2.2 Caius Plinius Secundus (Pliny the Elder) (23 - 79 sau cng nguyn)Plinius, mt nh t nhin hc v nh vn La M, mt nhn vt quan trng trong chnh ph v qun i. ng c gng hon thnh 37 tp Bch khoa ton th vi u Historia Naturalis (Lch s t nhin), quan trng l cc tp ni v cy thuc. Mc d cn cha nhiu nhc im nhng nh hng ln n thc vt hc chu u cho ti sau thi Trung c.

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2.2.3 Pedanios Dioscorides (Th k th nht sau cng nguyn)Nh phu thut qun i La M Dioscorides l nh thc vt quan trng nht sau Theophrastus. Cng vi qun i, i khp ni ng ta c nhng hiu bit v cy c dng lm thuc. Ni bt nht trong vic ci tin vic phc v y t trong ch La M, Dioscorides chun b mt cun sch ni ting Materia medica, m t 600 loi cy thuc. V sau b sung nhng hnh v l tng cho cun sch. Cun sch ny c nghin cu 1500 nm nay, khng c mt v thuc no c cng nhn l chnh thc tr nhng v c cun sch t tn. Mt bn sao ni ting v p nht c chun b khong 500 nm sau cng nguyn i vi Hong Flavius Olybrius Anicius lm qu cho con gi, Cng cha Juliana. Bn nguyn gc hin nay cn lu Vin (Dioscorides, 1959). Nhiu tn c Dioscoride dng nay vn cn gi tr. "Materia medica" cha cc loi cy t hn cc cng trnh ca Theophrastus nhng tnh hu ch ca n v cy thuc c coi nh l mt cng trnh v gi cho ti cui thi Trung c.

2.3

Thi Trung c

Sut thi trung c chu u, nhng nghin cu khoa hc v thc vt hu nh gim chn ti ch, cc cuc chin tranh v s suy tn ca ch La M gy ra s ph hoi rt ln trong vn hc. Nhiu bn tho b mt, nhng kin thc v thc vt ch gii hn nhng cng trnh c bit trc y ca Theophrastus, Plinius v Dioscorides.

2.3.1 Thc vt hc o HiT khong nm 610 n 1100 sau Cng nguyn, mt vi cng trnh thc vt c in c bo v bi o Hi bi v cc hc gi o Hi rt ngng m cc hc gi Aristotele v cc hc gi Hy Lp khc. T lng yu thch khoa hc ca h i vi thin nhin th dc hc v y hc ca ngi o Hi pht trin rt cao. Nhng nh thc vt o Hi thnh lp cc danh mc cy thuc nhng nhng s phn loi nguyn gc khng c pht trin.

2.3.2 Albertus Magnus, (Bc s tng hp) (1193 - 1280)Albertus Magnus vit v lch s t nhin v v cy thuc sut thi Trung c. Cng trnh thc vt ca ng De Vegetabilis khng ch gii quyt vi cc cy thuc nh cc cng trnh trc y Hy Lp v La M m cn km theo bn m t cc cy, l nhng bn m t tuyt vi, da trn nhng quan st u tin v cy. Tc gi c gng phn loi cc cy trn c s cu trc thn, s khc nhau gia mt v hai l mm v tin tng ln u tin s c tha nhn. Khi thi k phc hng bt u lm sng li kh th khoa hc v nhng thch th v thc vt tng ln. S in n v pht minh cho php nhiu cun sch thc vt hc c xut bn. l mt iu kin ln hn so vi cc bn tho chp tay trc y. Cc cun sch xut bn vi nhng bn m t v hnh v lm bng g hay kim loi mc ch dng xc nh cc cy thuc. Nhng cun sch hay cc cy c c dng thu thp v thu hi cy thuc. Nhng ngi lm vic c c gi l cc bc s hay thy thuc. Cc thy thuc vit v mc ch cho ngi s dng.

2.3.3 Nhng nh nghin cu thc vt c

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Vo th k 16, c l trung tm ca cc hot ng v thc vt. Nhng ng gp ni ting trong thi k di dng cy thuc nh Brunfels (1464 - 1534), Jorme Bock (1489 1554), Valerius Cordus (1515 - 1544) v Leonhard Fuchs (1501 - 1566). Brunfels Bock v Fuchs c coi l nhng ngi cha ca thc vt hc c. Cun sch ca Brunfels cha cc nh rt tt. ng l mt nh vn sm nht thi phc hng c vit v thc vt, cun sch ca Bock l nhng bn m t tuyt diu v m u cho mn phn loi hc mt cch c h thng. Cn cun Lch s thc vt ca Cordus nm 1540 ti 1561 mi xut bn (17 nm sau khi ng ta cht) m t hoa v qu ca 446 loi. ng ta m t di dng mt h thng phn loi da trn nhng nghin cu cy sng. Cun sch lch s Stiprium ca Fuchs gii thiu m t vi cc hnh v km theo c gi tr ph bin tt nht v c gi tr trong thi k . Nhiu kin thc thc vt c tng kt trong cun cc thy thuc c nhng thiu cc h thng phn loi km theo.

2.3.4 Thc vt cc nc hay nn vn minh khcNhng hot ng v thc vt Anh th k 16 c William Turner (1510 - 1568) v John Gerard (1542 - 1612); c c Charles de LEcluse (1526 - 1609), Renubert Dodoens (1517 - 1585) v Mathias de LObel (1538 - 1616), c Pierandrea Matthiolus (1500 - 1577) cng b nhiu ln cng trnh ch gii v hnh v ca Dioscorides. Nhng hot ng v thc vt thnh hnh khp chu u. Aztecs ca Mexico pht trin cc vn thc vt, cc cy trng lm thc n v lm cnh v nhiu cy thuc c s dng. Bn tho ca Aztecs xut bn vo nm 1552. Nn vn minh Trung Hoa c c nhiu thnh tu trong sut thi Trung c hn l nn vn minh Ty u. Ngi Trung Quc in trn giy trc nm 1000 sau Cng nguyn. H rt yu thch thc vt v nhp nhiu loi trng. Cc cng trnh thc vt cng b chnh thc 3600 nm trc Cng nguyn, tuy nhin bn tho c nht cn tn ti khong 200 nm trc Cng nguyn. Nm 2000 trc Cng nguyn, nn nng nghip n pht trin v nhiu cy lng thc c trng. Mt cng trnh thc vt rt th v ca n c vit vo th k th nht cho thy cc phng php trng trt rt ni ting.

2.4

S chuyn tip ca nhng nm 1600

Nhiu cuc thm him Tn th gii vo nhng nm 1600 pht hin nhiu cy mi. chu u nhiu nh thc vt nghin cu nhng thc vt v b sung nhiu cy mi. V s loi mi c pht hin rt nhiu, cc nh thc vt cn phi c h thng chnh xc hn t tn v sp xp chng theo mt trt t nht nh. V vy mt lot cc cng trnh h thng phn loi ra i.

2.4.1 Andrea Caesalpino (1519 - 1603)Caesalpino l nh thc vt ngi k tc l lun v tnh logic ca Aristotele. Tc gi cng b cun De plantis libri nm 1583 v cho rng vic phn loi phi dng trit hc hn l tnh thc dng thun ty bng cch da vo cc c im ca cy. Quan im c nh hng ln n cc nh thc vt v sau nh Tournefort, Ray v Linnaeus.

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2.4.2 Caspar Bauhin (1560 - 1624)Nm 1623, Bauhin, mt nh thc vt Thy S, cng b Pinax theatribotaniei thng k 6.000 loi cy. Pinax cung cp nhiu tn ng loi. l ti liu rt c gi tr v b ch. Chnh ng ta dng tn gi hai t. Cc chi cha c m t nhng xc nh c im ca cc loi trong chi.

2.4.3 John Ray (1627 - 1705)Nh sinh vt ngi Anh, Ray cng b nhiu cng trnh. Tuy nhin hai cng trnh ni ting nht v thc vt hc l Methodus Plantarum Novo (Ray, 1682) v Historia Plantarum (Ray, 1686 - 1704) vi 3 tp. Cng trnh u ti bn cui 1703 nghin cu 18.000 loi, nhiu loi trong s nm ngoi chu u. Ray pht trin h thng phn loi da trn mi quan h theo tng nhm cy ging nhau. S phn loi ca ng ta l ng gp ln nht v mt l thuyt ca th k 17. H thng Ray nh hng ln n Jussieu v De Candolle v sau.

H thng Ray v Bauhin c th coi l s bt u ca cc h thng phn loi t nhin tc l cn c vo s ging nhau tp hp theo tng nhm ca nhng cy ny vi nhng cy khc m ngy nay s ging nhau l c h hng vi nhau. Tuy nhin ch n thi ac Uyn nhng tng v mt xch lin kt mi xy dng c mt cch chc chn.

Hnh 2.1 Linnaeus (1707-1778, theo Swingle, 1946)

2.4.4 Joseph Pitton de Tournefort (1656 - 1708)Tournefort, nh thc vt ngi Php ni ting vi cng trnh Institutiones rei herbariae xut bn nm 1700, cng trnh rt ph cp v n d xc nh gm 9.000 loi thuc 700 chi. So vi h thng ca Ray, h thng ny mang tnh nhn o nhiu hn. Mc ch cun sch l nh loi. Tc gi nhn mnh ch yu bc chi. Mc d quan im ca ng c in hn Aristotele nhng i khi c coi nh l ng t ca quan im chi. ng ta c quan im chi r rng v c bn m t cc chi . Nh s phn loi chi c hnh thnh kh hon thin. C bng chng khi ng ta bt u pht trin h thng nhm bc cao hn chi.

2.5

Carl Linnaeus (1707 - 1778) v thi k Linnaeus

Linnaeus l nh thc vt Thy in t th k 18, sinh Roshult (Hnh 2.1) i khi c coi l ngi cha ca phn loi hc. Cho n nay h thng tn gi v tn gi hai t ca ng vn l bt h. Linnaeus vo trng Tng hp Lund nm 1727 v hc v y hc. Khng thch Lund ng chuyn sang trng Tng hp Uppsala nm 1729, Dean, Olaf Celsius gii thiu ng vi gio s thc vt hc Rudbeck. Trong chuyn thm him Lapland 1732 ng tip thu nhng hiu bit ln v lch s t nhin. Nm 1735, ng n H Lan v nhanh chng hon thnh bng Bc s trng Tng hp Harderwijk. Khi H Lan ng tr thnh bc s ring cho ch t giu c George Clifford, l ngi rt thch thc vt v cy trng, ng ta tr thnh ngi bo tr cho Linnaeus. Ba nm H Lan v i khp chu u l nhng thi gian

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quan trng v sng to ca cuc i Linnaeus. Trc khi tr v Thy in vo nm 1738 ng xut bn nhiu sch lch s t nhin. ng gp nhiu nh khoa hc ni ting lc nh Frederick Gronovius v Hermann Boerhaave H Lan, gio s J. J.Dillen v ngi Hans Sloane Anh v cc anh em h Jussieu Php. Sau khi tin hnh thc tp v y hc, ng tr li Thy in vo nm 1738 v tr thnh gio s v y hc v thc vt hc ti trng i hc Tng hp Uppsala vo nm 1741 v lm vic y cho n khi mt vo nm 1778. Ba cng trnh ni ting nht ca ng l Systema Naturae (1735) gii thiu h thng phn loi tng qut, Genera Plantarum (1737) cung cp nhng bn m t ca nhiu chi v Species Plantarum (1753), hai tp tra cu xc nh cy v chng c ti bn nhiu ln v lu tr nhiu th vin ln. Linnaeus m ra mt k nguyn mi v thc vt hc. Hin nay chng ta coi cng trnh ca tc gi nh l tt nh ca s sng to trong vic xy dng h thng nh loi v phn loi thc vt. Mc d h thng ch dng nh loi, mi quan h t nhin cha cp nhng nhng cy khc nhau c nhm li thnh nhm vi nhau. Linnaeus chia thc vt thnh 24 lp da trn s lng, s dnh v chiu di nh. Thc vt mt nh t trong lp Monandria, hai nh - Diandria v tip theo Triandria, Tetrandria, Pentandria v.v. Cc lp c chia thnh b trn c s s vi trong mi hoa. Hin nay chng ta coi ng gp ln nht ca Linnaeus l h thng tn gi hai t. Trong Species Plantarum ch tn chi, mt on m t c nh xc nh loi ging nh kha lng phn v mt tnh ng loi c in mp. V d xem di: Xem mc Glauca Serratula Tn chi: Serratula, tn th ba l glauca on m t: Foliis ovato-oblongis. Serratula glauca l tn hai t Nhng thng tin khc nhau: Cng b v hnh v trc y mu thu Virginia do J. Clayton thu cng b bi Gron. (Gronovius) trong Virg. (Flora Virginica) trang 116 Cng cy c tn sm hn l: Centaurium nudedium marianum cng b bi Plkenet bi Plukenet, trong Alm. Bot. Mantissa trang 40. V tn khc l S. marilandica cng b bi Dillenius, trong Elthamensis trang 354, bng 262, hnh 341.

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Linnaeus khng phi l ngi u tin cho tn hai t m trc Bauhin v nhng ngi khc gi nhng cha n nh. Tn gi ca Linnaeus sng mi n nay. Hn ch ca ng l ch mi s dng mt c im m chnh tc gi cng hy vng phi s dng nhiu c im. y l mt h thng hon ton nhn to, ngn cn s tin b trong phn loi thc vt. Khi phn tch cng trnh ca Linnaeus phi xem xt iu kin th k 18 nhng tnh trng nhm ln v tn gi thng xy ra, vo lc y Linnaeus s dng v tng hp cc tng t cc cng trnh ca Bauhin, Caesalpino, Ray, Tournefort v nhng nh thc vt khc. Linnaeus v ca ng t hp tt nht m ra mt k nguyn mi - thi i ca h thng nhn to. Cc b su tp ca ng do ngi v bn cho J.E. Smith nh thc vt Anh, mt trong nhng ngi sng lp hi Linn Lun n. Bch tho Linn hin nay t Lun n. Cc mu c chp nh v lu gi trong nhiu th vin.

2.6

Cc h thng t nhin

Vo cui nhng nm ca th k 18 nhiu nh thc vt nhn thc rng c mi quan h t nhin trong thc vt. Cc h thng phn loi nhn to ca Linn b phn i mnh m c bit Php bi v cc loi khc nhau li nhm li vi nhau v d cy h Xng rng vi cc loi mng nc chng hn. Do s pht trin h thng phn loi phn nh mi quan h t nhin nhm mc ch phn loi tr thnh mc ch ln ca cc hot ng thc vt hc lc by gi. H thng phn loi t nhin khi thy c xy dng v hon chnh phn nh k hoch ca thng v khng c cc mt xch lin kt.

2.6.1 Michel Adanson (1727 - 1806)Nh t nhin hc Adanson n vng nhit i chu Phi, h thc vt v ng vt nhit i lm cho ng nhn ra rng h thng phn loi da vo mt c im l khim khuyt. H thng phn loi ca ng l da trn nhiu c im c coi ngang bng nhau. ng khng ng quan im xem c im ny quan trng hn c im kia v ng m t nhng nhm tng t nh b v h chng ta hin nay gi m nhng bc c Ray ngh trc y nh B th t trong Familles des Plantes (1763). Tuy nhin khoa hc phn loi hc thy rng mt s c im ny c gi tr hn c im khc m cc nh phn loi hin i c gng dng cng nhiu c im cng tt. Nhng phng php ca Adanson tm thy s ng h trong nhng nm gn y ca nhng nh phn loi s lng khi h s dng my tnh phn loi da trn tt c cc c im c th o m c.

2.6.2 J.B.P. de Lamarck (1744 - 1829)Nh sinh hc Php Lamarck hiu rt r v nhng c gng khng thnh cng ca mnh khi gii thch tng v tin ha nhng ng li l nh phn loi hc thc vt ni ting Php. Trong thc vt ch Php xut bn nm 1778 ng xc nh cy no trc, cy no sau trong cc lot t nhin v ng tm lut trong vic nhp cc loi, cc b v cc h li vi nhau.

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2.6.3 Anh em h De JussieuC bn nh thc vt trong h Jussieu. Ba anh em Antoine (1688 - 1758) gim c Vn thc vt Paris; Joseph (1704 - 1779) nh thm him v thu mu Nam M v Bernard (1699 - 1777) ngi sng lp Vn thc vt hong gia Vecxy v chu trai ca h Antoine Laurent (1748 - 1836) ngi sng lp Bo tng Lch s t nhin Paris nm 1793. Trc cch mng Php mt t, mt quyt nh sp xp cc cy trong vn thc vt Vecxy theo h thng Linn. Vn thc vt khng sp xp theo h thng ny v Bernard de Jussieu thy rng cc cy trng tng t nhau (c ngha l c quan h h hng) nn c gp li vi nhau. iu ny khng phi lun lun l ng theo h thng gii tnh ca Linn m theo h thng nhng cy khng ging nhau hp li thnh nhm v chng c cng s nh. Tuy nhin nn nh rng tng tin ha v cc mt xch cho n thi ac Uyn mi c xy dng. Nm 1763 Antoine Laurent de Jussieu cng vi ch bt u mt cng vic xp cc cy theo nhm mt cch t nhin trong vn. Nm 1789 sut thi cch mng Php, ng cng b Genera Plantarum secundum ordines Naturaees disposita. Cng trnh a ra mt h thng t nhin c chp nhn rng ri; 100 nhm hin nay c coi l h m ng gi l b. y l nghin cu ni ting m nay vn c chp nhn. H thng Jussieu hn hn h thng Linn v l c s cho s pht trin xa hn ca h thng phn loi t nhin.

2.6.4 Gia nh De CandolleDanh ting ca gia nh De Candolle c bt u bi Augustin Pyramus de Candolle (1778 - 1841) (Hnh 2.2). Mc d sinh Geneve, De Candolle c o to ti Paris v chu nh hng ln ca cc nh thc vt Php lc by gi, nm 1813 cng b Thorie lmentaire de la botanique trong nu cc nguyn tc phn loi thc vt. S phn loi ca ng khc vi h thng Jussieu nhng l mt h thng phn loi t nhin. C gng ln ca A. P. de Candolle (t 1816 n khi cht 1841) l b Prodromus systematis Naturaeis regni vegetabilis. B sch phn loi v m t tt c cc loi cy c mch bit. D cha xong, l mt cng trnh nghin cu trn phm vi th gii ca mt vi nhm. By tp u do tc gi vit v mi tp tip do cc chuyn gia vit v ti 1873, Alphonse con trai ca De Candolle hiu chnh xut bn.

Hnh 2.2 A.P. de Candolle (1778-1841) (theo S.B. Jones, Jr.; A.E. Luchsinger, 1979)

2.6.5 George Bentham (1800 - 1884) v Joseph Dalton Hooker (1817 - 1911)S ch ca cc nh thc vt trong sut na u th k 19 l nhm pht trin v sa i cc h thng phn loi t nhin, nh cao ca thi i ny l cng b Genera Plantatum ca Bentham v Hooker (1862 - 1883). Bentham t o to tr thnh nh thc vt ngi Anh v Hooker l gim c vn thc vt Hong gia Kew gn Lun n, cun Genera Plantatum l mt cng trnh c ba tp bng ting La tinh, cho cc tn v m t tt c cc chi cy c ht. H thng phn loi m n sp xp r rng xut pht t h thng ca Jussieu v

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De Candolle. Genera Plantarum l mt trong nhng cng trnh ln nht m quan im loi da trn tng rng loi l nhng thc th c nh khng thay i qua thi gian v c to ha sinh ra trn Tri t. Mc d n hnh thnh sau ac Uyn v quan im loi l tin ac Uyn. Tuy nhin, ranh gii h v chi l da trn mi quan h t nhin phn nh di sn ca Jussieu. Mt nguyn nhn l cun sch rt c ch thm ch c by gi, hai ng chun b m t chi t nhng quan st thc t m khng phi sao chp theo cc ti liu tham kho. Nhng bn m t chi l chnh xc v y , cc chi ln chia thnh cc nhnh v phn nhnh cng nh s phn b a l. H thng phn loi ca h c chp nhn v s dng rng ri cc h thc vt thuc a Anh v cc ni khc. Cc bch tho Anh nh Kew v Bo tng Anh vn c sp xp theo n.

2.7

nh hng ca l thuyt tin ha acUyn i vi h thng hc

Vo gia th k 19 l mt giai on bt u ca tng tin ha. Cc quan st v su tp ca nhng ngi du lch th gii v nhng dng v tn cc mu vt tr li chu u lm cho n khng th qun nhng tri thc v ha thch ghi nhn v nhng bin d ca cc loi thc vt v ng vt. Lch s l thuyt v tin ha kch thch nhng nghin cu v h thng phn loi thc vt. Charles ac Uyn (1809 - 1882) v A. R. Wallace (1823 - 1913) vit mt bi bo vi u The tendency of species to from varieties and species by naturae means of selection c trc Hi Linn Lun n 1-6-1858. Vo 24-11-1859 cun Ngun gc cc loi ca ac Uyn ra i do vy, khoa hc v sinh vt c nhng thay i ln. Th k 20, quan im coi loi khng phi l bt bin m lun lun thay i, c mi ngi chp nhn. Cc th h v tn ca loi to ra ging nhau, loi l h thng cc qun th bin i v thay i theo thi gian v to ra cc lin kt gia cc c th c h hng gn gi.

2.8

Cc h thng pht sinh chng loi chuyn tip

Do tc ng ca hc thuyt ac Uyn, nhng nh phn loi bt u i n thng nht quan im tin ha th hin trong s phn loi ca h. Nhng h thng sau ac Uyn da vng chc trn hnh thi hc thc vt. Cc nh phn loi c gng sp xp cc nhm cy t nhin trong dng tin ha t n gin nht ti phc tp nht.

2.8.1 August Wilhelm Eichler (1839 - 1887)c l trung tm i u nghin cu hnh thi thc vt trong sut na sau ca th k 19. Vic phn loi trong thi k l c nht v hnh thi v cc nh hnh thi hc thc vt c bt u xem xt cc s liu ca h di nh sng thuyt tin ha. S lng cc cng trnh ng gp rt ln. Trong cng trnh quan trng nht l Eichler (cng b 1883) c nhiu ngi chp nhn. ng chia gii thc vt thnh thc vt khng ht (Cryptogamae) v thc vt c ht (Phanerogamae). Dng th nht gm Nm, To, Ru v khuyt thc vt; nhm th hai gm Ht trn Gymnospermae v Ht kn - Angiospermae. Angiospermae li chia thnh hai nhm Mt l mm - Monocotyledoneae v Hai l mm - Dicotyledoneae. Eichler khng chp nhn hay t nht l khng hiu khi nim tiu gim th sinh (tc l t hoa phc tp thnh hoa n gin), iu c th hin khi t v tr mt s nhm trong s phn loi.

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2.8.2 Adolf Engler (1844 - 1930) v Karl Prantl (1844 - 1839)Engler l gio s thc vt hc Trng i hc Tng hp Berlin v Gim c Vn thc vt Berlin t 1889 - 1921 (hnh 2.3) ng ta ngh mt h thng phn loi da trn h thng Eichler ch khc v chi tit. Cng vi Prantle ngi gip vic ca ng cng b Die Naturalichen Pflanzenfamilien trong nhiu tp t 1887 n 1915. Cng trnh gm cc kha, bn m t tt c cc h thc vt, nhiu hnh v. Hai ng o to nhiu mn tip tc s nghip ca mnh. Cun sch ca hai ng c mt gi tr thc tin ln hn nhiu so vi gi tr v phn loi ca n. S ca Engler c nhiu ngi cng nhn bi v tnh chi tit v tng hp ca n. Hu ht cc bch tho khng phi ca Anh v nhiu h thc vt trn th gii vn theo cch sp xp ca cun sch . Hnh 2.3 Engler khng c nh xy dng h thng theo tin trnh tin ha. Adolf Engler (1844-1930) ng ta tin rng hoa n c v n tnh l nguyn thy v cng (Theo S.B. Jones, Jr.; A.E. Luchsinger1979) trnh trc , ng ph nhn s tiu gim th sinh. H thng phn loi ca ng c tip tc kim tra bi nhng mn ca ng ta v cng b nhiu ln trong Syllabus der Pflanzenfamilien. Tp hai ca ln xut bn 12 v ln cui cng c Melchior hiu chnh cng b 1964. Qua qu trnh sa cha, v tng th c mt s thay i nh mc d mt s h thay i trong h thng phn loi. H thng Engler hin nay c coi nh l li thi v hu ht cc nh thc vt khng ng vi kt lun v hoa nguyn thy.

2.9

Cc h thng pht sinh chng loi

Cc h thng phn loi m h thng phn nh s tin ha gi l pht sinh chng loi. Vo th k 20, s tc ng ca ch ngha ac Uyn v di truyn hc ln ton b h thng hc thc vt v cc h thng phn loi c ngh u th hin tnh pht sinh chng loi, mt trong nhng thnh tu v h thng l cha nhiu thng tin. Thc t h thng pht sinh chng loi v h thng t nhin tng t nhau. Cc chi v h hu nh khng khc nhau, s khc nhau l v tr sp xp h v b cng nh coi hoa g l nguyn thy. Trng phi Engler xem hoa n c, n tnh l nguyn thy. V d hoa nguyn thy theo Engler s ging nh hoa n tnh ca Salix hoc Populus. H thng pht sinh chng loi coi hoa nguyn thy theo ngha hoa t tin v chng c nhiu cnh trng, nhiu l i, nhiu nh t do v nhiu l non ri xp xon nh hoa Magnoliaceae - Ranunculaceae. Ngoi ra ht phn l mt rnh cha c mch. Nhng h nguyn thy thnh thong dnh cho t hp Ranales. Thut ng nguyn thy n gin ha theo vn cnh ca Engler l mt khi nim xut pht t nguyn nhn trong khi vn cnh chng loi pht sinh nguyn thy ngha l ci g u tin. Theo cc nh c thc vt hc, t hp Ranales c trng l u tin v vy nhng c tnh cht l nguyn thy.

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2.9.1 Charles E Bessey (1845 - 1915) (Hnh 2.4)Gio s Trng i hc Nebraska, Bessey c Asa Gay o to, mt nh thc vt Harvard. Bessey l ngi M u tin c ng gp ln cho l thuyt phn loi thc vt. Nm 1894 do nh hng ln ca t tng ac Uyn, mt h thng phn loi pht sinh chng loi da trn nguyn tc tin ha ca cht hu c cng b. ng coi cy c hoa l n nguyn xut pht t mt dng tin ha l i din cho mt chui mt xch lin tc. H thng da trn mt b nhng cu chm ngn hay l nhng quan im v du hiu nguyn thy tm thy trong cc thc vt c n nhng c im tin b nhng cy tin b hin nay. H thng ca ng l h thng ca Bentham v Hooker thay i vi s nhn mnh gc Ranales l nguyn thy v pht trin ln cc thc vt hai l mm v mt l mm khc. S phn loi cui cng ca tc gi khc cng b ngn gn c tnh khi qut sau khi ng mt vo nm 1915.

Hnh 2.4 Charles Bessey (18451915) (theo S.B. Jones, Jr., A.E. Luchsinger, 1979)

2.9.2 John Hutchinson (1884 - 1972)Nh thc vt Anh, Hutchinson hp tc vi vn thc vt Hong gia Kew. Trong cc cng trnh ca ng Families of flowering plants (1973) v Genera of flowering plants (1964 - 1967) ng a ra h thng phn loi ging nh h thng Bessey nhng khc rt nhiu c tnh c bn. c bit nht Hutchinson cho cy c hoa xut pht t nhm tin c hoa gi tng (c ngha l nhng cy trung gian gia Ht trn v Ht kn) v chia thnh ba dng: Mt l mm, Hai l mm thn tho, Hai l mm thn g. Mt l mm nguyn thy xut pht t Hai l mm nguyn thy thn tho, im xut pht trong Ranales. Hutchinson coi dng g tin ln dng tho l hng quan trng nht trong hai l mm. Dng g xut pht t dng cy g v dng cy tho t dng Ranales cy tho. Cng trnh Hutchinson v cc h, chi ring l v c bit i vi Mt l mm l hon ho. S phn chia Hai l mm thnh dng cy g, dng cy tho c xem l khng t nhin v nhng h hng gn gi li t xa nhau.

2.10 Cc h thng phn loi hin iHin nay, cc h thng phn loi gii thc vt tip tc c ci tin v nhng thng tin cng ngy cng cp nht. Trong nhng nm gn y, cc h thng phn loi cy c hoa c b sung nhiu dn liu c thc vt, sinh ha, di truyn, nhng thng tin siu cu trc qua vic s dng knh hin vi qut v knh hin vi in t truyn hnh. Nhng ti liu dng lin kt vi cc thng tin thu t cc phng php truyn thng nh gii phu so snh, t hnh thi hc. Nh phn loi thc vt M, Robert Thorne cng b mt tm tt h thng ca mnh vo nm 1968 v trnh by chi tit hn vo nm 1976. Armen Takhtajan (1969, 1970, 1987, 1989, 1997) nh thc vt Nga; Arthur Cronquist (1968) nh thc vt M, h gii thiu tng quan v cc h thng phn loi ca h. Ba h thng ny u da trn h thng Bessey v h thng truyn thng trn nguyn tc tin ha vi nhng thng tin hin i nht.

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Chng 3 Loi v s hnh thnh loi3.1 Loi l g*

Phn loi hc l da trn s ging nhau hay khc nhau ca cc c th. Trc y phn loi hc l mt khoa hc m t da trn s bin i cc du hiu hnh thi. S phn loi ca cc nh phn loi hc th k 18 - 19 t cc c th ging nhau trong mt nhm gi l loi. Cc loi ging nhau xp thnh mt chi v cc chi ging nhau xp thnh mt h. Vi nhng tin b ca ch ngha ac Uyn vo cui th k 19 quan im v loi tin ha xm nhp vo phn loi. L thuyt tin ha ac Uyn cho rng loi l nhng dng cc loi trong mt chi c quan h tin ha vi nhng nhnh h hng; chi v h i din s phn ha t xa xa trong dng tin ha . Trc ac Uyn ngi ta cho rng loi do thng to ra v khng bin i theo thi gian. l tng ca ng sng to c bit. Quan im loi ca ac Uyn dn n s pht trin cc s phn loi pht sinh chng loi. Phn loi pht sinh chng loi tin on v mi quan h pht sinh chng loi t quan im ng ta cho tng v h thng phn loi n nguyn. Cc chi, h, u phn nh quan nim l cc thnh vin trong mi nhm u c mt ngun gc chung. Th no l loi hnh thi Trong thc t, mt nhm c th thc vt c nhng nt c bn ging nhau c coi l mt loi. V l tng, loi c th tch ra bi cc c im hnh thi khc nhau vi cc loi h hng. l iu cn thit c s phn loi thc t m qua c th gip ngi khc c th phn loi c. i khi kh c th xc nh ranh gii loi chnh xc theo quan im loi pht trin, cc mu vt c coi nh l mu vt sng sinh ra cc qun x gm nhiu c th lin quan vi nhau v di truyn. Nhiu kiu khc nhau v loi c pht trin do cc c ch v tin ha hay di truyn khc nhau. V vy trong khi thu mu, mt nguyn tc phi thu nhiu ni, nhiu mu thy c y cc mc phn ly trong mt loi, trnh c s nhm ln khi thu cc mc phn ly thnh cc loi khc nhau. Cc loi khc nhau c c ch tch bit sinh sn khc nhau; c ch hoc gim s lai hoc ngn cn s lai cho. V d nh nhiu loi sinh sn hu th, mt s sinh sn hu th, mt s do qu trnh a bi, s bin i s th nhim sc hoc c ch khc. Mt loi ang trn ng tin ha, trong h thng qun th sng c th tm thy nhiu giai on khc nhau hay mc khc nhau ca s phn ly v hnh thi. Tm quan trng ca s phn ly b nh hng bi Fosberg (1942) - ng ta quan st rt nhiu qu trnh tin ha, cc giai on phn ly khc nhau. Th no l loi sinh hc Trong thc t loi sinh hc kh p dng c vi cy. Cc loi lng bi kh c th trao i gen, nhng v mc ch thc tin, cc mc a bi khc nhau trong cc loi hnh thi c coi l mt loi khi nhiu cy tip xc chng c th trao i gen v c th lai hu th. Th h lai u tin gia cc loi gii hn kh nng hu th t hu th hon ton n mt phn hoc bt th hon ton. V nguyn nhn ny hay nguyn nhn khc, kh nng hay mt kh nng cho con lai v trao i gen khng th dng nh l mt tiu chun lm gii hn loi

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trong phn ln thc vt. Tm li loi sinh hc bao gm nhng qun th, m cc c th trong cc qun th c th lai vi nhau v cho con ci c kh nng sinh sn bnh thng.

Loi Loi

Phn loi (kiu sinh thi)

Loi

Phn loi (kiu sinh thi)

Hnh 3.1. S phn ly ca mt loi trong mi trng tng i ng nht thnh cc phn loi c mi trng phn bit v c th thnh hai loi nu s phn ha ca cc qun chng tip tc.

Nhng taxn di loi (trong loi)

Mt loi cha nhiu bin i trong cc qun th ca n, ba bc trong loi c quan tm trong phn loi thc vt v c cng nhn chnh thc l phn loi, (subspecies), th (varietas) v dng (forma). Phn loi v th c p dng cho cc qun th loi cc giai on phn ha khc nhau. Qu trnh chung ca tin ha v hnh thnh loi trong thc vt l phn tch t cc loi hay h thng cc qun th ng nht v hnh dng thnh hai hay nhiu h thng qun th (Hnh 3.1). S phn ha c lin quan n s thch ng vi cc khu a l hay kh hu khc nhau hoc vi cc a phng m cc sinh cnh sinh thi tch bit nhau. Sut qu trnh thch ng i vi sinh cnh khc nhau cc qun th a phng s c s tch bit nhau v di truyn. S phn ha v di truyn c th hin qua cc c im va hnh thi v va sinh l, thng cc qun th phn ha hay cc kiu sinh thi chim nhng ranh gii cnh nhau, y chng giao phi vi nhau. Thng c s t qung t t hay t ngt trong nhng m hnh bin i gia cc qun th khc nhau ty theo th nng ca mi trng. Cc kiu sinh thi thng to thnh c s cho s phn ha thnh cc phn loi hay th. Forberg (1942) cho rng cc giai on phn ha c th c ch ra cc bc trong loi m cc qun th loi quy nh. iu gip cho cc nh phn loi hc gii quyt mt cch mm do bng cch a ra cc bc trong loi. Th l bc trong loi u tin c dng. Theo Linn l nhng bin dng u tin do mi trng to ra. Phn loi c Persoon a ra t nhng nm u ca th k 19 c coi nh nhng bin i ln ca loi. Gray (1887) coi th l mt bin i ln trong loi. Nm 1926, Hall gii thch rng thut ng th c nhiu cng dng rt nhiu ci khc nhau t ni (race) n ging cy trng (cultivar). Mt s khc nh Fernald coi th nh mt s phn chia a l ca loi v phn loi nh mt phn ca t hp loi. Trng phi California do Hall

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thnh lp s dng thut ng phn loi v trng phi ng Fernald ng h s dng th i vi n v trong loi. Trong thc t phn loi v th c cng nhn l nhng bin dng v hnh thi. Cc qun th ca chng c mt m hnh ring, s bin i ty thuc vo s phn b a l v i hi v sinh thi. Bc phn loi v th c p dng thng ty thuc vo tng ni v tng nh phn loi hc, ty theo tp qun hay t tng ch o ca h. Dng ni chung c cng nhn v m t l nhng bin i lc c, v d cy hoa t ngt mt s cy c hoa trng. Nu hoa trng khng c lin quan vi bt k nhng c im ca cy nh s phn b a l hay sinh thi th chng c gi l dng. ngha phn loi thp i vi phn loi nh hay ri rc m t tch ra cc dng c mt s t nh phn loi hc hin i dng, nht l khi nghin cu v cy cnh.

3.2

S hnh thnh loi lin quan vi bin i v tin ha

Cng vi tnh a dng, tnh phc tp v cu trc v bn cht thch ng ca cy, cc nh h thng hc m t cc taxn, pht hin cc h thng phn loi v lm sng t qu trnh tin ha. Cc nh h thng hc c gng pht hin c ch v cc qu trnh trong Thc vt c hoa: 1) hng tin ha ca chng, 2) nh hng ca cc m hnh bin i v 3) nguyn nhn hnh thnh loi. Cc nh phn loi c in nhn mnh sn phm cui cng ca s tin ha v s khc nhau gia cc taxn. S tin ha cht hu c l nhng dng chuyn tip ca cc nguyn liu di truyn ca cc qun th qua thi gian, l do s chn lc t nhin ph hp vi nhng tng tc ca mi trng (Dobzhansky et al, 1977). Tin ha khng ng ngha vi s hnh thnh loi. Tin ha l s tch ly t t ca nhng bin i nh v mt di truyn qua nhiu thi gian dn n s hnh thnh loi (Stebbins, 1950).

3.2.1 Ngun bin iTnh phc tp v a dng ca i sng thc vt th hin trong loi v gia cc c th trong cng mt loi. Nhng dng bin i to ra c s ca tin ha v phn loi. S tin ha cy c th c pht hin bng vic phn tch cn thn cc bin i , cc nh h thng hc thng chia vi nhng bin i trong cc qun th c ba thnh phn: 1) bin i pht trin, 2) bin i do mi trng v 3) bin i do di truyn. 3.2.1.1 Bin i pht trin Cy gi thng khc hn cy mm. S bin i pht trin ny c quy nh v mt di truyn. L gi ca Eucalyptus mc cch v thng xung trong khi l non ca nhiu loi mc i v xp ngang theo trc ng. L cy mm ca Fraxinus l n nhng l gi l kp lng chim. V giai on ht l thi k c tnh cht quyt nh nht trong i sng thc vt, cc tnh cht tn ti trong sut thi k c tnh quyt nh gi tr sng. L cy mm dng kim ca Juniperus v Thuja c kh nng quang hp hn l vy nh trong cc cnh gi. Cc nh h thng hc sinh hc nghin cu s khc nhau v pht trin trong vn v nh knh, trong sut chu trnh sng. S bin i v pht trin l nhng iu th v tm hiu hnh thi v tin ha. 3.2.1.2 Bin i mi trng

28

Cc thc vt hon ton bin i v mt s loi c th bin i bng cch thay i m hnh sng ca chng p ng vi s bin i ca mi trng. Hin tng hc thay i do s thay i nh sng, nc, cht dinh dng, nhit v t. V d c in c tm thy trong mt s loi Sagittaria. Nhng cy c l hnh mi tn khi nh ln, l dng di khi chm lt theo dng chy ca nc v bu dc rng khi nm trn mt nc. Loi Ranunculus aquatilis (hnh 3.2) c l b ct x khi chm trong nc nhng trn cng thn s c l x thy khi nh cao khi mt nc. Loi Stellaria media ni ngho v kh ch cao 3 cm v ni t m v tt cao qu 20 cm. Cc nh phn loi phi pht hin v phn bit nhng bin i ca mi trng. iu lun lun xy ra cy ng gen trong nhng iu kin khc nhau. Khi th nghim vi nhng cy hoang di, biu hin bn ngoi lun lun bin i khi mc trong cc mi trng khc nhau (Clausen, Keek and Hiesey, 1940) nhng tnh cht m d dng bin i l kch thc cy, cc c quan, s lng cnh, l hoc hoa. Nhng tnh cht kh bin i theo iu kin mi trng l s phn thy, rng, lng ca l, kch thc, hnh dng v s lng cc thnh phn ca hoa. Tnh nhy cm c gi tr sinh tn v ng gp cho s tin b ca c th v n cho php cy iu chnh theo mi trng m chng sng.

Hnh 3.2. Loi Ranunculus aquatilis vi l chm v l ni mt nc (Weaver & Clemnt, 1938)

3.2.1.3 S bin i di truyn Bin i di truyn l kiu th ba ca cy (bin i genotyp). Bin i gen m c th k tha do hai ngun: 1) t bin v 2) Phiu bt gen v ti t hp. t bin l s bin i kh nng truyn trong nguyn liu di truyn. l ngun bin i cui cng trong loi v b sung kh nng bin i di truyn. Khi dng rng ri, thut ng bao gm c t bin gen v t bin im (thnh vin nucleotit) v t bin th nhim sc. * t bin gen:

29

t bin gen l s thay i v tn s ca cc phn t nucleotit m n s lm i hng nhng hot ng gen (Grant, 1975). thc vt bc cao, nhng t bin gen c th hin nhiu tnh cht. Vai tr ca t bin gen trong s bin i tin ha ty vo mt s nhn t: 1) tng gi tr nh hng ca chng ln c th, 2) u vit thch nghi hay khng thch nghi ca cc c th t bin v 3) vai tr gen t bin trong s tng tc gia qun th v mi trng. Mi trng m trong t bin xut hin s c nh hng ln n mi lin kt ca n trong cc qun th a phng. Tr khi mi trng ang bin i, cc t bin chc chn mc thch ng thp nht ca loi. Nu loi iu chnh tt vi mi trng sng th nhng t bin nh chc c th cho php n tn ti trong mi trng mi hay mi trng ang bin i, tr nhng bin i mnh chc chn lm ngho chc nng ca n. Con lai gia hai kiu sinh thi ca Potentilla glandulosa chng minh rng nhng tnh cht ca chng c kim tra bi mt lot gen gi l gen bi (Clausen, 1951). Nh cc gen bi, s khc nhau v tnh k tc trong nhiu c tnh lun lun c xc nh bi hai hay nhiu gen c lp c tc dng ging nhau v tng cng (Grant, 1975). Mi mt trong cc qun th ca Potentilla chuyn ha hoc thch nghi tn ti di mt s iu kin c bit. Tnh thch nghi ca Potentilla tch ly nhiu bin i nh qua thi gian hn l nh t bin (Grant, 1963). * t bin th nhim sc Nhng t bin th nhim sc gm: 1) s tng bi cn ca b th nhim sc (Polyploid), 2) tng bi lch (aneuploid) tc l mt i hay thu thm nhng th nhim sc v 3) thay i ton b cu trc. Thay i cu trc c th: 1) thiu hay mt mt on ca th nhim sc, 2) gp i mt on, 3) s i ch mt on. S thay i trong cu trc ca th nhim sc khng sinh ra cc gen mi nhng chc nng lin quan ti vic ti t hp gen c o, s sp xp gen mi v nhng nhm lin kt khc nhau (Stebbins, 1971). * Phiu bt gen v ti t hp S vn chuyn v trao i gen gia cc qun th nui trng c m t nh phiu bt gen. S ti t hp l kt qu ca cc t hp gen c trc y. Phiu bt v ti t hp c lin quan ti cc gen sn c trong t nhin. Nhng qu trnh l ngun bin i chnh nhanh chng trong t nhin v c mang n do th tinh cho gia cc c th, cc qun th v cc loi. Ti t hp to ra s sp xp cc gen mi do th tinh cho, do chuyn on ca cc th nhim sc tng ng tip theo bin i s t hp c lp ca th nhim sc khi phn bo. Nhiu bin i kiu gen trong qun th c th do ti t hp ca cc gen khc nhau m cc gen tn ti trong nhiu th h. Tim nng ca nhng thay i lun lun c trong cc qun th c tm quan trng ln (Grant, 1963). Tnh a dng v sinh ha c chng minh mt cch r rng s tn ti ca kho bin i ln trong cc qun th t nhin ca cc c th khc nhau (Avise, 1974; Hamrich and Allard, 1975). - Kiu sinh sn: Cc kiu sinh sn ca thc vt phi hiu nh gi s ti t hp. S sinh sn gm: 1) th tinh cho, 2) t th tinh, 3) sinh sn dinh dng t n v 4) sinh sn v tnh t ht (khng c s th tinh) (Grant, 1971). Nu sinh sn dinh dng hay sinh sn v tnh hng n thay th sinh sn hu tnh, qu trnh gi l t sinh (apomixis) (Stebbins, 1950). T sinh ph bin trong cc thc vt c lin kt vi s lai trong loi v a bi cao. l chng trnh sinh sn m n lin quan n s phn b th nhim sc trong phn bo (Grant, 1970). T th tinh hng n gim s ti t hp nhng s th tinh cho lm tng s ti t hp.

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3.2.2 Chn lc t nhin cho s bin i tin ha xy ra, phi c mt ngun bin i di truyn v sc mnh iu khin. Sc mnh u tin c gi l chn lc t nhin v l quan trng nht trong qu trnh tin ha. H qu s chn lc t nhin l s thch nghi hay l s iu chnh vi iu kin mi trng. S chn lc t nhin l c ch m nh cc qun th c bin i p ng vi iu kin mi trng (Grant, 1963). Chn lc t nhin thc hin vi s sinh sn khc ca mt s kiu gen. Cc kiu gen c li chin thng trong qu trnh sinh sn. S thch ng ca thc vt cho php chng sng thun li trong iu kin mi trng sng. Chn lc t nhin thit lp v gi li nhng t hp gen trong phm vi t nhng bin i n gin n nhng bin i c lin quan n dng sng ca cy.Cc m hnh chn lcChn lc nh hng Chn lc n nh Chn lc ph hu

Cc th h

Loi b Loi b Loi b

Loi b

Trung bnh

Trung bnh Gi tr di truyn

Trung bnh

Hnh 3.3. Ba kiu chn lc: nh hng, n nh, ph hy (Grant, 1977)

Cc nh tin ha m t ba loi chn lc: 1) n nh, 2) nh hng v 3) ph hy (hnh 3.3, Grant, 1977) nhng ci c xc nh bi mi trng sng ca chng. Chn lc n nh c li cho nhng c th bnh thng tc l loi b nhng bin dng khc vi dng chnh v t nhiu n nh vi mi trng. Chn lc nh hng xy ra trong mi trng bin i nhiu hng tc l nhng bin i t m n kh tip theo l nhng thay i v m hnh thi tit. Chn lc phn ly gy p lc ln mi trng khng ng nht to ra nhng chn lc ph hy. iu b gy qun th ng nht thnh cc qun th con khc vi qun th m lc u theo cc hng khc nhau, v d nh s hnh thnh cc kiu sinh thi thch ng vi cc iu kin mi trng a phng ring l.

3.2.3 S bin i trong qun th v s phn ha ni gingNhiu nm th nghim chng minh mt cch r rng rng cc qun th loi cy c hoa a phng bin i rt ln. S bin i th hin qua cc c im hnh thi v s khc nhau bn trong nh l Allozym, th nhim sc, cc sn phm ca cy... (Heslop - Harrison, 1964). S bin i dng (bin i t t) v khm ca cc kiu sinh thi khc nhau tch bit c th c cng nhn. Cc kiu m hnh ty thuc vo s phn b a l v sinh thi ca loi c

31

lin quan. Cy g rng, nhng cy c trn ng c v nhng cy khc mc trn nhng din tch ln m trong iu kin mi trng thay i t t hng n s thay i dng. Tuy nhin nhng thc vt chim nhng lnh th m ni b tch ra thnh cc khm ca cc iu kin sinh thi mt cch r rng th s hng n nhng bin i v khm. Nhng m hnh khm thng lin quan n iu kin t ai v m. Trng th nghim l mt k thut ln pht hin nhng s bin i v bn ngoi ca loi v khm ph s khc nhau gia cc kiu sinh thi (Langlet, 1971). Vo u th k 19, A. P. de Candolle trng nhiu dng cnh nhau. Vo gia th k 19, cc nh thc vt Php A. Goldan trng so snh nghin cu nhiu loi hoang d Php pht hin ra nhiu bin dng kiu sinh thi. ng tch ra thnh nhiu loi Linn. V d nh ng chia Erophila varna thnh 200 thc th m hin nay chng c gi l Gordanol. l kt qu ca s tch bit. Vo nhng nm 20 ca th k XX, V. Turesson trng th nghim ch ra s phn ha v di truyn ca cc c th. ng dng thut ng kiu sinh thi cho nhng ni sinh thi thch ng v ngh mt thut ng sinh thi hc gen gii quyt vn sinh thi hc ca cc kiu sinh thi (Langlet, 1971). Turesson iu tra mt s loi cy ph bin pha Nam Thy in m mc trong cc sinh cnh khc nhau. Khi mu ca cc loi mc trong nhng vn ng nht th ng thy chng c phn bit bi s lng cc c im ch r ca s phn ha v mt di truyn. ng ta chng minh cc kiu sinh thi v mt kh hu v th nhng trong cc loi cy tho sau mt thi gian ngn Edinburgh. J. W. Gregor nghin cu chi M cng chng minh cc dng sinh thi. iu ch ra v mt di truyn l c nhng bin i t t trong loi, n lin quan n iu kin mi trng. Cng trnh c in Bc M c tin hnh bi mt nhm cc nh khoa hc: Jens Clausen, nh t bo hc; David Keck, nh phn loi hc, William Hiesey, nh sinh thi hc. Vo nhng nm 30 th k trc, h xy dng nhng th nghim ba v tr California v y c phn bit mt cch r rt v kh hu v cao (Clausen, 1951). Mt th nghim c t trng i hc Tng hp Stanford cao 1212m, mt khc Mather v pha Ty ca Sierra Nevada 1400m v th ba Timberline cao 3000m gn nh ca Sierra Nevada. Trong nghin cu ca mnh, h chn nhng cy lu nm mc dc theo lt ct t bin ti nh ni cao. H la chn nhng cy m chng mc thnh bi. Nhng cy ny c th c phn chia to ra nhng nhm ng nht v mt di truyn m chng c trng ln lt trong ba vn (hnh 3.4).

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Thung Lch H lng Yosemite Tenaya Aspen

ng c Tuolumne

H Big Horn

nh Conway

Vng Sierra Nevada

Cao nguyn Great Basin

Thi Bnh Dng Vng ven bin

Thung lng Jacquin

Hnh 3.4. S phn ng ca cc chng ca loi Achillea trng trong vn Stanford. Nhng cy ny c ly t lt ct ngang ngTy ca Trung Carlifornia. Nhng mi tn ch ra ngun gc ca cc qun chng, cn s ch ra nhng bin i v cao v cc cy tiu biu (Clausen, 1951)

Hnh 3.4. S phn ng ca cc chng ca loi Achillea trng trong vn Stanford. Nhng cy ny c ly t lt ct ngang ng-Ty ca Trung Carlifornia. Nhng mi tn ch ra ngun gc ca cc qun chng, cn s ch ra nhng bin i v cao v cc cy tiu biu (Clausen, 1951)

33

Nh vy nhng cy ng nht v mt di truyn c so snh trong cc mi trng khc nhau ca mi vng. Cng trnh ca h chng minh mt cch r rng rng cc qun th a phng c s thch ng ring bit vi mi trng ring ca chng. Cng trnh nghin cu California t c s cho hng nghin cu v sinh thi gen hin nay v c nh hng n cc nh phn loi thc vt (hnh 3.5). Hu ht cc loi c phn chia do s phn b ca chng cng nh m hnh nui trng thnh cc qun th a phng nh (Grant, 1963). iu cung cp tng trong s chn lc t nhin c th xy ra lm bin i gen m khng cn tr nhng phiu bt gen t nhng qun th bn cnh. Nhng qun th a phng c th c phn ha v mt sinh thi v a l v to thnh cc kiu sinh thi khc nhau. Cc kiu v loi sinh thi nh th c th l c s ca cc phn loi v th trong phn loi hc. Nhng ni thun khit vi ngha l h thng qun th ng nht khng tn ti trong t nhin (Grant, 1963). Thay th vo , nhng s khc nhau v a l v sinh thi hc tm thy trong cc m hnh c biu din trong (hnh 3.6). Nhng ni bnh thng mang tnh nguyn vn, nu chng tip tc c tr th ni s to ra nhng vng sinh thi trung gian. Nu cc loi c m t v cho tn th chng c gii hn bi s t qung r rng trong m hnh bin i ca chng. S pht trin mi ca di truyn hc qun th lm cho c th nghin cu nhng kiu gen ca mt c th mt cch ngu nhin v pht hin nhng bin i trong cc locut gen ring bit (Dobzhansky et al., 1977). Nhng thng tin di truyn c M ha trong cc tn s nucleotit ca phn t ADN v c chuyn thnh cc aminoaxit, to nn cc prtin hoc enzym. Nhng bin i trong prtin c coi l nhng bin i v gen. in di gel c cc nh di truyn s dng pht hin cc cu thnh ca aminoaxit trong cc prtin hoc enzym ring l. Prtin v enzym c tch ra t cc b phn ca cy. Cc cht tch chit c t trong gel. Gel cng vi cc cht chit ph thuc vo dng in. Mi mt prtin trong mu s chuyn dch trong trng in ca gel theo mt tc ty thuc vo kch thc v trng lng cc phn t ca chng. N c th c nhn thy bng cch s dng cc cht mu dng cho mt s prtin v enzym. K thut nh vy cho php pht hin s bin i di truyn v c p dng rng ri. Vo khong 15 hoc 20 enzym hoc prtin ring bit c nghin cu coi nh l tnh ton v nhng bin i trong qun th, khng phi tt c cc bin i u c pht hin bng cch s dng in di. Mc d k thut in di c mt vi hn ch nhng nhng nghin cu chng minh rng nhiu c th c kh nng ln trong bin i di truyn.

34

Timberline Cht Cht Cht Cht Cht Cht

Mather

Stanford

Hnh 3.5. S phn ng ca cc c th loi Achillea borealis vng ven bin Carlifornia khi chuyn vn thc vt Stanford (gn bin) Mather (4000 phit) v Timberline (10.000 phit)

35

Vng trung gian gia cc chng qun a phng Cc chng qun a phng

Th nng mi trng theo vng a l ca loi

Hnh 3.6. Gii hn (vng ln) ca cc loi v cc qun chng a phng c s phn ha a l v sinh thi v cc vng trung gian. Ni chung cc loi khng lin tc trong ton phm vi m ch xut hin ni thch hp.

Hnh 3.5. S phn ng ca cc c th loi Achillea borealis vng ven bin Carlifornia khi chuyn vn thc vt Stanford (gn bin) Mather (4000 phit) v Timberline (10.000 phit) Hnh 3.6. Gii hn (vng ln) ca cc loi v cc qun chng a phng c s phn ha a l v sinh thi v cc vng trung gian. Ni chung cc loi khng lin tc trong ton phm vi m ch xut hin ni thch hp.

3.3

S hnh thnh loi v s tch bit

Stebbins (1950) nhn mnh rng nguyn tc quan trng nht xut hin trong qu trnh tin ha l s tin ha v ngun gc ca loi. nh ngha hin nay v loi nhn mnh tm quan trng ca tnh lin tc v di truyn v hnh thi trong loi v tnh t qung gia cc loi h hng gn gi. Cc nh h thng hc nhn thy rng mt dy nhng bin i di truyn c th tn ti trong loi. Cc n v di loi l da trn s tch bit cha hon ton v mt hnh thi, do cn phi tng cng s tch bit v sinh thi v a l. Hai nhn t l cha kha khng nh s tch bit v mt di truyn. Tuy nhin cc n v phn loi vn tn ti bng s trao i gen hn ch v s thch ng vi mi trng a phng.

3.3.1 S tch bit v sinh snC ch tch bit l nhng hin tng hc m n s ngn cn s lai to gia cc n v gn gi. Chng da trn nhng nhn t sau: 1) s cch xa v khng gian, 2) cc nhn t mi trng, v 3) sinh hc sinh sn. C ch tch bit lun lun c t ra mt trong hai phm tr, c ch trc hp t l c ch ngn cn s th tinh hoc c ch sau hp t l c ch xy ra sau s th tinh. Nhn chung hu ht cc v d tch bit trong thin nhin c gii quyt bng cch t hp ca mt hoc nhiu c ch hn l mt c ch ring l. S tch bit a l tn ti gia hai loi m gii hn a l ca chng c tch ra bi nhng ch trng ln hn bn knh pht tn ca ht phn v ht. Platanus occidentalis v P.

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orientalis mc t nhin Bc M v a Trung Hi. Chng phn bit v mt hnh thi v tch bit v khng gian rng. Khi mang v trng vi nhau trong vn chng cho con lai c kh nng hu th. Khi khu phn b hai taxn khng chng ln nhau th cc loi c gi l xa nhau. Khi khu phn b hai loi chng ln nhau th cc loi trng nhau.

3.3.2 S tch bit v sinh thiL do phn ha ca mi trng sng i hi. Mc d cc thc vt sng trong cng mt ni nhng s lai cho b ngn cn bi v sng trong nhng sinh cnh khc nhau. Hai loi Vernonia mc vng trung du Gorgia, V. noveborcensis sng ven ng hoc ng c m c nhiu nng v V. glauca sng trong vng cy g cng that nc v chu bng y c hai loi u sng trong cng mt vng nhng con lai t khi c mc d ngi ta c th lai to rt d dng trong nh knh... S khc nhau v di truyn c kim tra trong cc du hiu sinh sn v nhng thi quen m cng c th lm cn tr s trao i gen. Nhng loi cng khu phn b c th b cch ly theo ma v s ra hoa xy ra trong nhng thi gian khc nhau. S cch ly gia hai loi trn c tng cng bi s khc nhau v thi gian ra hoa. Mt loi n r vo gia ma h cn ma kia vo cui ma h. S cch ly v dn tc hc l mt c ch rt quan trng i vi ng vt, n c lin quan n nhng thi quen thm ving hoa ca mt vi cn trng v chim. Mt s Chim, Ong v Bm m cng nh cc cn trng v chim khc c tnh chuyn ha c bit, chng c s nhy cm v th gic gip cho n c kh nng phn bit c cc hoa trn c s mi v, mu sc, hnh dng... (Grant, 1963). V d nh Chim rui b thu ht bi nhng hoa mu , cn Bm m b thu ht bi hoa mu trng. Mt s vt truyn phn th n nh cho tng loi hoa v chng c bn nng n thm mt loi hoa no trong qu trnh thm ving. Tnh u vit ca tp qun n thm cc loi hoa ca cc cn trng l vn hiu qu ca nng lng (Heyric v Raven, 1972). Mt nhm cy c lp c hoa pht trin mt ni no v nhng c ch nhn bit hoa, mt loi cn trng s thu nhn c nhiu mt hoa v ht phn trong mt thi gian ngn bng cch thm ving ca mt loi. S khc nhau v cu trc trong cc b phn ca hoa c th s ngn cn s th phn cho. S cch ly c hc xy ra trong nhiu h vi cu trc hoa phc tp nh Thin l v Phong lan. Trong c hai h , ht phn thng c dnh li trong ti phn hoc khi phn vi kch thc v hnh dng khc nhau. Cc ti phn ring l chc s c nh bi vt mang phn, s mang n nhng ch h trn b nhy. V tr ca phn trn cn trng c th l trn u hoc di ngc rt quan trng i vi vic truyn phn c hiu qu cao (Digldodson, 1966). S th phn gia cc loi khng cn phi dn n s hnh thnh nhng con lai hu th. Nhiu bc pht trin s xy ra trong s th phn v sn xut con lai hu th. Nhng chng ngi ca s pht trin s xut hin cc giai on khc nhau trong khi to ra nhng cy trng thnh hu th c ngha l cc ng phn s khng t n non, cc non s khng t n trng hoc l hp t kt hp s b cht i, ni nh y gy ra s cht ca phi, qu khng pht trin y , s lng ht tiu gim, ht khng ny mm, cc cy non b cht, cc bao phn b thui, cc giao t bt th (Grant, 1963).

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V bt th ca con lai, cc con lai th h u tin c to ra v n hoa nhng nhy b thui hoc cc ht phn khng in hnh b thui i, tnh bt th ca con lai c th ch mt phn pht trin. N khng th gy ra do s tch ra khng bnh thng th nhim sc trong phn bo. S gp i s lng th nhim sc c th mt phn vt qua nhng kh khn phn bo nhng khng nh hng n tnh bt th ang pht trin. Tnh bt th tch ra l do s chuyn ch, o v sp xp li cc th nhim sc khc, cng nh do s khc nhau v cu trc bn trong ca th nhim sc. Con lai gia hai loi c th th hin nhiu mc tiu gim trong tnh hu th. Mt vi con lai s hon ton hu th, mt s khc na hu th cn s khc na bt th hon ton. S ngn cn cui cng ca s trao i gen gia cc loi, ph v con lai xy ra trong th h th hai hay cui cng. Trong mt s giao nhau gia cc loi Veronya, nhng con lai th h u hon ton hu th nhng th h th hai c nhng bin i lin tc t hon ton hu th n hon ton b cht i. Nhng nguyn nhn dn n s ph v con lai cha c hiu mt cch y nhng c th c lin quan n cu trc th nhim sc, n hm lng gen v cng nh s khc nhau bn trong cu trc ca th nhim sc. iu gy ra nhiu kh khn cho s pht trin, m nhng kh khn lin quan n sinh l hc v s hnh thnh ca giao t. C ch cch ly pht trin bng cch to ra s phn phn ly tin ha v cc phn ca h thng qun th phn bit v mt sinh thi, hnh thi v sinh ha. Cc vt cn ca s trao i gen bt u pht trin. V d nh s c mt ca truyn phn, c bit vi s lng ln trong mt phn ca khu phn b loi chc phi qua s chn lc t nhin to ra nhng knh thch ng ca cu trc hoa hng n ph hp nht i vi cn trng . S thch ng t t v s khc nhau trong cu trc ca th nhim sc trong mt phn ca qun th s dn n ngun gc vt chn th nhim sc. Ngun gc cc c ch cch ly khng phn bit vi bt k cc kiu tin ha khc.

3.4

S hnh thnh loi

L s phn ly tin ha v s phn ha ca h thng qun th ng nht u tin thnh hai hay nhiu loi cch bit. S hnh thnh loi i hi s bin i di truyn m s bin i bao trm trong cc h thng qun th cng thm s cch ly. Vo nhng nm 60 ca th k XIX, nh ng vt hc ngi c Wagner (1889) v nh thc vt o Kerner (1896 - 1897) a ra mt tng rng tnh phng x a l v sinh thi ca cc qun th l song song bi s phn ly v sinh l v hnh thi. Nh ng vt hc ngi M Mayr v cc nh tin ha lun khc nhn mnh s cn thit ca khong cch khng gian i vi s hnh thnh loi. Quan im ny thit k nn l lun a l ca s hnh thnh loi. C s ca tng ny l mt nguyn tc m trc khi cc qun th c th phn ha th phi c mt sc p v s phn ly chn lc t nhin. Nhng iu kin ni chung thng gp trong bt k s phn ly no m c th to nn mt c ch cch ly hoc i vi ni hoc loi (Grant, 1963). Thm vo yu t phn ly phi c cch ly v mt di truyn ban u s khng b ln t bi s trao i gen vi nhng qun th bn cnh. Trong mt s nhm ng vt h hng, s phn ha prtin v enzym c lin quan cht ch n s phn ly hnh thi thnh cc ni phn loi, loi hoc chi (Avise, 1974). C hai kiu thay i tin ha c bn: tin ha ngnh, loi v tin ha phn ly. Theo thi gian m trong loi phi tin ha thnh ci g khc vi t tin ca n c gi l tin ha ngnh. Ngc li, h thng qun th duy nht n l m n tin ha phn ly thnh hai ng ring l gi l tin ha phn ly. V cc qun th s phn ly v mt di truyn nn c ch tch bit cch ly cng bt u pht trin. S cch ly sinh sn mt phn tn ti ph bin trong cc

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qun th a phng ca loi do s cch qung v khng gian, ma ra hoa, nhn t th phn, yu cu sinh thi... S phn ly ca cc kiu sinh thi p ng vi mi trng s cng c thm mt kiu sinh thi c chuyn ha i vi mi trng ca n, c ch cch ly c th c xy dng s trao i gen. V s phn ly tng ln, cc yu t ca qun th c th ngy cng t c kh nng trao i cho. S phn ly s dn n s cch ly v s cch ly s to iu kin cho s hnh thnh loi, c ngha l s kin ny s thc y s kin kia. C nhng cuc tranh lun khng th kt thc v c s phn ly m khng c s cch ly a l hoc l s hnh thnh loi trong vng phn b c th xy ra. S hnh thnh loi trong vng s gy ra vng phn ha i vi qun th h hng gn gi m cc qun th cng chung sng trong mt khu phn b a l. Cu tr li cho iu cha c lm sng t. V mt l thuyt, kh nng hnh thnh loi trong vng hnh nh l chc chn hn nu cc cy t th tinh bi v iu s dn n s thu hp dng gen. Mc d nhiu nh tin ha lun gim mc ti thiu s phn ha trong vng v n chc l xy ra di s phn ly mnh m, s phn ly sinh thi, s tiu gim v lai to xa hoc l s thay i cu trc trong th nhim sc. Trong mt v d c s phn ha nhanh (40 - 60 nm) ca cc qun th Anthoxanthum v Odoratum mt loi b lai xa trn nhng tiu chun 20 x 35m c pH ph hp (Snaydon, 1970). S bin i th nhim sc khng lin quan n sinh thi a l c thng bo California.

3.4.1 Lai toVai tr ca lai to trong hnh thnh loi v tin ha l mt ch tranh lun trong phn loi hc (Grant, 1963), Linn ngh ngun gc lai i vi mt s loi cy. Vo cui th k XIX, u th k XX, ngi ta tin rng lai to c th l im xut pht ca loi mi. Mi n nhng nm 50, cc nh thc vt min cng cng nhn nhng con lai trong t nhin. Hin nay cc nh h thng hc thc vt coi con lai gia cc loi l ph bin trong mt s chi. Chi Si v chi Hng dng c cc loi m cc loi kh c th xc nh c bi v chng l s lai to gia cc loi.

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Mc tch bit

Chi

Thi gian

Loi

Ni a l Ni a phng

Qun th t tin

Cy phn ly

Hnh 3.7. Cc giai on phn ly. S phn ly tng th s tch bit tng

S lai to trong thin nhin ph bin trong cc cy nhiu nm hn l cc cy mt nm. Bn cht cy nhiu nm m bo rng s lai to ngu nhin gia cc loi khng cn tr n s tn ti chng. T cc kiu gen c gi bng cc dng sng nhiu nm. Tuy nhin khng c s chn lc mnh chng li s lai to trong nhng cy nhiu nm. S lai to gia cc loi ph bin trong thc vt nhiu hn l trong ng vt. C mt s nguyn nhn l: 1) s cch ly dn tc hc c hiu qu hn i vi ng vt, 2) cc nh ng vt c th b qua mt vi s lai to bi v ng vt khng phi d dng thu mu nh vi thc vt, 3) v cu trc phc tp v tn s pht trin ca ng vt c quan h vi thc vt, s lai to chc chn hn gy ra cn tr trong vn tng tc v pht trin gen ng vt hn l thc vt. Con lai nhn chung th h th nht c nhng c trng l trung gian gia cc loi b m. Nhng con lai nh th i din cho s giao phi cho gia nhng b m c thch ng tt v pht trin bnh thng. Nhng con lai ca th h th nht cng thng c tnh cht trung gian v cc nhu cu sinh thi ca chng. Chng thng c s yu th v cnh tranh t khi mi trng ang bin i (tr khi ni sng trung gian c sn). Hai loi cng khu phn b c th tch bit nhau v sinh thi. Mt loi mc trong ni m cn loi kia mc ni kh. Mt v d ca iu xy ra gia Vernonia faciculata v V. bandwii Tip theo s lai to t nhin khi con lai th h th nht quay tr li vi loi b m. C mt vi nguyn nhn xy ra, nhiu cy c kiu gen b m tn ti s tng kh nng lai cho vi cc thnh vin trong nhm b m. Tnh hu th ca con lai c th thp hn so vi chng to ra, cc ht phn t c kh nng sng st hn l b m. Tuy nhin hu ht hiu qu lai gia cc loi c hin tng lai tr li lai vi b m. Kt qu trong vic tha k (s tr li) ca con lai hng n kiu b m. Cc con lai lai ngc thng thnh t hn v chng c xu hng t n nh cao ca s thch ng ca b m chng. S lai ngc c th gy ra trong s vn chuyn ca gen t loi ny n loi khc qua con lai v ngc li. l s lai o. S lai o c th dn n lm bin i trong cc m hnh bin i ca b m bi dng gen.

Cc giai on

40

nh hng chung ca s lai to phn ln ty thuc vo mi trng m y n xy ra. Trong mi trng n nh, chc chn khng c nh hng quan trng trong mi trng khng n nh mi hoc ang bin i th cc con lai c th thch ng tt hn b m ca chng bi v con lai thng c lin quan n ni sng b tc ng m Anderson (1949) to ra l mt giai on, mt sinh cnh lai.

3.4.2 Th a biS tng i b th nhim sc l mt trong nhng qu trnh t bo hc ph bin v tch bit nht. N th hin s tin ha ca cy c hoa (Stebbins, 1971). Khong 40% cc loi cy c hoa v t l cao hn i vi Dng x l a bi. nh hng hnh thi v sinh l ca th a bi c th hin kch thc t bo tng, tiu gim s phn chia t bo, thay i v hnh dng, cu trc cc b phn ca cy, tnh hu th thp v c s khng cn bng v sinh l. V mt truyn thng, th a bi pht trin t mt loi c bit nh l mt hin tng t a bi hoc t hai loi b m gi l ng a bi hay lng a bi. Tuy nhin, tnh trng cc trng thi trong thin nhin phc tp hn nhiu so vi iu v tnh trng a bi t nhin thng c s t hp khc nhau ca th nhim sc. Nhng giao t khng tiu gim (2n) do khim khuyt ca phn bo c th t hp cho ra th t bi (Horlan v de Wet, 1975). Th a bi c th sinh ra t khim khuyt ca phn bo c t trong sut qu trnh pht trin m iu v sau pht trin thnh hoa a bi (4n). Cng ging nh lai to, th a bi thng lin quan n cc dng sinh trng. Nhng cy mt nm c khuynh hng tn s a bi thp nht v cy tho nhiu nm c tn s a bi cao hn cy g. S lai gia cc loi thng xy ra trong cc th a bi vi s lai cho gia cc loi b m vi con chu lai cc mc a bi khc nhau lm m i s tch bit gia cc taxn.

3.4.3 T pht sinhS thay th sinh sn hu tnh bng sinh sn v tnh gi l s pht sinh. Qu trnh thng rt ph bin trong Thc vt c hoa v Dng x, thnh thong xy ra trong cc n hoc chi dinh d