Comparative Leaf Morphology and Anatomy of some Nigerian ...

Journal of Science Research (2014) Vol. 13: 23-36

ISSN 11179333

Comparative Leaf Morphology and Anatomy of some Nigerian Rattans(Arecaceae – Calamoideae Beilschm.)

1Jayeola, A.A. 2*Aworinde, D.O. and 3Ogundairo, B.O.

AbstractCollections of 14 species of rattan palms were made from forest habitats along the coastal areas and major forestzones in Nigeria. The aim was to study the leaf morphological and anatomical characters of the palms with a view tofacilitating their identification. Morphological characters as well as anatomical features were examined. Analysis ofvariance (ANOVA) indicated significant differences (p≤0.05) among morphological characters such as trichomelength, internode length, cirrus length and leaf width. Trichomes were present in all the species except inAncistrophyllum novum Burr. and Laccosperma robustum (Burr.) [J. Dransf.] Presence of uniseriate epidermis,ergastic substances, sunken stomata and peripheral arrangement of vascular supply was noted and the significance ofthis is discussed in relation to the family Arecaceae. The high demand of rattan products has been a serious concernwith respect to the sustainability of rattan species worldwide. Conservation methods to ensure continued use ofrattan palms might be to sensitize farmers, foresters and users on the overall biology of rattan palms and theircultivation techniques.

Key words: Anatomy, Rattan palms, Taxonomy, Nigeria.

IntroductionThe rattans of Africa are represented by thethree endemic genera Laccosperma (G. Mann& H. Wendl.) Drude, Eremospatha (G. Mann& H. Wendl.) H. Wendl. and Oncocalamus(G. Mann & H. Wendl.) as well as by a singlerepresentation of the Asian genus CalamusLinn. In Nigeria, they are represented by 14species and are of vast economic importance.The range of rattans extends from the sealevel to more than 300m elevation, fromequatorial rainforests to monsoon savannasand the foothills of Himalayas [1]. Thus, thelarge number of rattan species is matched bygreat ecological adaptation and diversity.

1Jayeola, A.A. 2*Aworinde, D.O. and 3Ogundairo,B.O.1Department of Botany, University of Ibadan, Ibadan,Oyo State, Nigeria2Department of Biological Sciences, Ondo StateUniversity of Science and Technology, Okitipupa,Ondo State, Nigeria3Department of Biological Sciences, FederalUniversity of Agriculture Abeokuta, Ogun State,Nigeria*Corresponding Author E-mail:[email protected]

Most, admittedly crude, ecologicalpreferences for rattan species have generallybeen identified during taxonomic inventorywork, yet these broad ecological summariesare invaluable as a basis for establishingcultivation procedures.

Generally, rattan species are found in awide variety of forest and soil types. Somespecies are common components of the forestunder-storey; others rely on good lightpenetration for their growth; hence, somespecies are found in gap vegetation and mayrespond well to canopy manipulation. Otherspecies grow in swamps and seasonallyinundated forest, whereas others are commonon dry ridge tops. Taxa such as Calamusdeeratus (G. Mann & H. Wendl.), C.pilosellus Becc., Laccosperma secundiflorum(G. Mann & H. Wendl.) Kuntze, L. leave (G.Mann & H. Wendl.) Kuntze andEremospatha wendladiana Dammer ex Becc.were found in a wide array of forest types,ranging from dry to wet habitat andoccupying all the strata of the habitat whereasothers exhibited restricted distribution. Thepetiole in most rattan palms is somewhatvariable in length [2]. Usually, it is much

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longer in juvenile than in mature leaves and itmay be absent altogether. The petiole, wherepresent, and the rachis are often heavilyarmed with spines and has been speculatedthat the spine is not necessarily adapted forthe climbing process but appear to function asa means of trapping light from the forestcanopy probably for the primary purpose ofnutrients accumulation [3].

In terms of utilization, [4] stated that thelargest demand for canes is for makingfurniture, for which they provide both framesand decorative trimmings and facings. [5]

noted that the unsplit canes are utilized asbroom handles, sewer rods, walking sticks,ski sticks and snow brooms, while split canesare used for chair seats and in basketryworks.[4] listed the uses of canes to includemats, handicrafts and souvenirs. Rattans have

also been used for items such as belts,wristlets, lashing of articles such as axe-heador other instrument heads to their handle [3].In spite of their diverse indigenous uses, littleis known about their leaf micro-morphology.The objective of this work was to elucidatethe leaf anatomical characters of the rattanpalms with a view to facilitating theiridentification, even from leaf fragments.

Materials and MethodsThe leaf specimens used were obtained fromliving collections made from forest habitatsalong the coastal areas and major forest zonesin Nigeria between the years 2006 and 2008during the periodic field trips (Fig. 1;Table 1).

Fig. 1: Geographical distribution of rattan species in Nigeria and the collection sites.

Laccosperma robustum

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Table 1: List of Representative Specimens Studied

F.R. = Forest Reserve; C.R.S. = Cross River State.

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The leaves were pressed and identified at theForestry Research Institute of Nigeriaherbarium (FHI) and University of Ibadanherbarium (UIH); voucher specimens weredeposited in the herbaria. Fresh specimenswere used for the anatomical investigation.From five specimens of each of the 14 taxastudied, 1cm2 portions were cut at the apical,median and basal regions of the preservedmature leaflets. Samples were revived byboiling in water and fixed in formaldehydeacetic acid (FAA 50%) for 24 hours [6]

followed by dehydration in series of ethanol(30-95%). Infiltration was done withparaplast (soft wax) and tissue mat (hardwax) using tertiary butyl alcohol (TBA) asbase for 24-48 hours at 50°C [6]. Infiltratedspecimens were transferred into theembedding liquid (melted wax poured intoimprovised moulds) to cast hard blocks.Trimming of the relatively hard polymerisedblocks was done with the aid of disposableknives. The transverse sections, about 13µm,were made with Leica 820 II rotarymicrotome available in the pathologylaboratory at the International Institute ofTropical Agriculture (IITA) Ibadan, Nigeria.Using, one-way disposable knife, eachsection was transferred into drops of warmdistilled water on a clean slide on whichadhesive had been previously rubbed. Thewarm distilled water served in a place ofwater bath for stretching the sections. Afterdrying on a slide warmer (Fisher slidewarmer SE 2417), slides were de-waxed inxylene and subsequently hydrated throughethanol series (5-30%). Staining was donewith safranin for 15-20 mins. andsubsequently rinsed in distilled water anddifferentiated ethanol series (30-95%);counterstained in fast green for 5secs,

transferred into xylene for 5mins., cleared inclove oil for 10mins. and mounted in DPX®

mountant. Anatomical descriptions followedthe conventions established by [6] as modifiedby [7]. Data were expressed as mean ± SD,and differences in means were assessed forsignificance at P≤0.05 by Duncan’s MultipleRange Test (DMRT) [8].

ResultsMorphologyQuantitative morphological parameters of therattans are presented in Table 2. The leafletwidth differs among the species of rattansstudied; it ranged from 1.9cm inAncistrophyllum novum Burr. andOncocalamus manni H. Wendl. to 24.1cm inCalamus pilosellus Becc. The leaflet widthsin Laccosperma secundiflorum andEremospatha hookeri are not significantlydifferent. The same trend was observed forAncistrophyllum novum and Oncocalamusmanni, and Calamus deeratus andEremospatha wendladiana. Mean number ofpaired leaflets of the species differs; thisranged from 4.5 in Laccosperma robustum(Burr.) J. Dransf. to 48 in Laccospermaopacum (G. Mann & H. Wendl.) andCalamus deeratus (G. Mann & H. Wendl.)The values observed are similar inOncocalamus macrospatha Burr. and O.acanthocuenis Drude both having 18 each.Also, the numbers of paired leaflets aresimilar in Oncocalamus wrightianus Hutch.,O. manni H. Wendl. and Calamus pilosellusBecc. each having 35. The remaining specieshave variable number of paired leaflets whichcould be diagnostic.

27

Table 2: Quantitative Morphological Parameters of the Rattans Studied

Values are mean ± SD; n=3. Means followed by the same alphabet in the same column are not significantly different (Spearman, p>0.05); n.p. = not present.

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AnatomyPhotomicrographs of the species studied arepresented in Plates 1-7. The epidermis iscomposed of rectangular cells with outerthickened wall and few sunken stomata. Theepidermal cells are in longitudinal files andare usually square or rectangular. One ormore cell layers immediately beneath theepidermis form a colourless hypodermis andoften indistinct. The peripheral bundles aresometimes irregularly and incompletely fusedto form an almost continuous peripheralsclerotic cylinder in Laccosperma robustum(Burr.) J. Dransf. The ground tissue of theleaf axis contains numerous scattered,longitudinal-running, large vascular bundlesamong which are interspersed occasionallywith small vascular bundles. The groundparenchyma of the central part of the axis wasuniform in all the observed genera. Thevascular tissues are sheathed by two distinctlayers; the outer sheath is parenchymayous,compact and always uniseriate. The cells areclearly distinguishable from the adjacentmesophyll cells which sometimes arerectangular or elongated as found inEremospatha macrocarpa (G. Mann & H.Wendl.) and E. hookeri H. Wendl. The innersheath is mostly sclerotic, often multiseriateand immediately surrounds the vasculartissue.

DiscussionThe morphological parameters observed in allthe species revealed that differences exist inthe internode length, cirrus length and leafletswidth, and such differences could be used inthe delimitation and identification of the taxa.The qualitative and quantitative charactersare not genus-bound. The characters occur insimilar proportions in different genera. The

correct identification of rattans is essential inestablishing priorities for conservation anduse strategies.

The absence of trichomes in Ancistro-phyllum novum and Laccosperma robustumwhich often is a reflection of physiologicalresponse to a combination of environmentalfactors could be useful for diagnostic purposeat the species level. This is in agreement with[9] who used trichomes to delimit five speciesof economic rattan in Ghana. The anatomicalvariation observed in this study shows thatthe most promising characteristic features inspecies separation are the trichome length,internode length and cirrus length. Thefeatures suggested by [10] for genericseparations are of little diagnostic value at thespecies level as many characters overlapamong the species. During ontogeny [11], theshape of the leaves changes with change inthe internode shape to avoid self-shadingwithin a crown; however, with the possiblecombination of several anatomical andmorphological characters, an experiencedplant anatomist could succeed in identifyingthe rattan species of Nigeria especially whenthe geographic source of the rattan is known.The unique mix of characteristics such asdurability and flexibility make rattan verygood raw materials for furniture andhandicraft industries [12]. The high demand ofrattan products has been a serious concernwith respect to the sustainability of rattanspecies worldwide [13]; among these concernsare their use as food, for furniture andhousehold handicrafts, habitat destruction,and little or no conservation efforts. Viablemethods to remedy the situation might be tosensitize farmers, foresters and users on theoverall biology of rattan palms and theircultivation techniques.

29

Plates 1a-c: Transverse sections of Oncocalamus macrospathus Burr. and Laccosperma secundiflorum (G. Mann &H. Wendl.) Kuntze leaf. a, apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) UE = uniseriateepidermis; ES = ergastic substances; PF = Phloem field.

→UE

→

→

PF

ES

←PF

30

Plates 2a-c: Transverse sections of Oncocalamus wrightianus Hutch. and Ancistrophyllum novum Burr. leaf. a,apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) UE = uniseriate epidermis; ES = ergasticsubstances; PF = Phloem field.

UEES→ ↓PF→

31

Plates 3a-c: Transverse sections of Eremospatha macrocarpa G. Mann. & H. Wendl. and Laccospermum robustum(Burr.) J. Dransf. leaf. a, apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) UE = uniseriateepidermis; ES = ergastic substances; PF = Phloem filed; DR = Druses.

←ES

UE↓ ↓PF

DR↓

32

Plates 4a-c: Transverse sections of Laccosperma opacum G. Mann. & H. Wendl. and Oncocalamus manni H.Wendl. leaf. a, apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) DR = druses; ES = ergasticsubstances; PF = Phloem field.

DR

ES

↓↓

PF↓→PF

33

Plates 5a-c: Transverse sections of Laccosperma leave (G. Mann. & H. Wendl.) Kuntze and Calamus pilosellusBecc. leaf. a, apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) UE = uniseriate epidermis; ES= ergastic substances; PF = Phloem field.

ES

UE↓ ↓

PF↓↓PF

34

Plates 6a-c: Transverse sections of Calamus deeratus G. Mann. & H. Wendl. and Eremospatha wendladianaDammer ex Becc. a, apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) UE = uniseriateepidermis; VE = Vessel element.

UE↓

→VE

35

Plates 7a-c: Transverse sections of Eremospatha hookeri H. Wendl. and Oncocalamus acanthocuenis Drude leaf. a,apical region; b, mid-region; c, basal region. (Scale bars = 100µm.) UE = uniseriate epidermis; PF = Phloemfield; DR = Druses.

UE↓←PF

↓DR

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