Section Two Stems Definition: important vegetative organ. Physiological function conduction supporting function preservation breeding Medicinal value.

Section Two Stems Definition: important vegetative organ.

Physiological function conduction

supporting function

preservation

breeding

Medicinal value

Herba Ephedrae Cortex Eucommiae

Medulla Tetrapanacis Lignum Aquilariae Resinatum

一、Morphological Features and types

of Stem

1. morphological features☆ Definition: node , internode ,

shoot

☆ buds In fact it is meristem or immature structure of developing organs.

According to the growth location of buds

Normal bud : terminal bud,axillary bud,accesory bud

Adventitious bud

The outer form of stem

1.terminal bud

2.Lateral bud

3.node

4.Leaf scar

5.internode

6.lenticel

According to the nature of the development of buds

Leaf bud

Flower bud

Mixed bud

According to the activity of buds

Active bud

Dormant bud

Naked bud Scaly bud

According to bud scales with or without

Way branching stems

1.Monopodial branching

2.Sympodial branching

3.Dichotomous branching

4.False dichotomous branching

☆2.Stem types woody stem: tree, shrub, subshrub, woody vine

herbaceous stem: annual herb, biennial herb, perennial herb, herbaceous vine succulent stem

erect stem

twining stem

climbing stem

screeping stem

☆ 3.Stem Modifications

①upper terraneous stem Leafy stem

Shoot thorn

Hook-like stem

Stem tendril

Tubercle,bulblet

False bulb

Abnormal

aerial stem

1.Leafy shoot

2.leafy stem

3.hook-like stem

4.Shoot thorn

5.stem tendril

6.Tubercle

7.bulblet

Anomalous aerial stem1.Leafy shoot （天门冬） 2. leafy stem （仙人掌） 3. hook-like stem （钩藤）

4.Shoot thorn （皂荚） 5. stem tendril （葡萄） 6. tubercle （示珠芽）

②Subterraneous stem

Rhizome

Tuber

Corm

bulb

abnormal subterraneous stem

Ⅰ.rhizome .rhizome .tuber .corm Ⅱ Ⅲ Ⅳ

Ⅴ.bulb 1.scaly leaf 2.terminal bud 3.bulb plate 4.adventitious root

Ⅵ. bulb

The abnormal subterraneous stem1.rhizome （姜） 2. tuber （半夏） 3. corm （荸荠）4.bulb （洋葱） 5.lognitudinal onion 6.bulb （百合）

二、 Inner Structure of Stem①Structure of Stem Apex

meristematic zone

elongation zone

maturation zone

②Primary Structure of Dicot Stems

epidermis （ trichome and stoma ） cortex vascular cylinder

Definition : endarch: The order of differentiation and maturation of primary xyle

m of stem is from the inside to outside, and is known as endarch.

Primary structure of Dicot st

ems

1、 epidermis

2、 cortex

3、 vascular cylinder

4、 collenchyma

5、 parenchyma

6、 phloem fiber

7、 primary phloem

8、 fascicular cambium

9、 primary xylem

10、 pith rays

11、 pith

双子叶植物茎的初生构造（横切）

Transverse section of sunflower

1 、 epidermis

2 、 collenchyma

3 、 resin canal

4 、 cortex

5 、 phloem fiber

6 、 pith rays

7 、 primary phloem

8 、 sieve tube

9 、 fascicular cambium

10 、 vessel

11 、 xylem fiber

12 、 xylem parenchyma

13 、 pith

③Secondary Structure of Dicot StemsA. Woody Dicot Stems

Fascicular cambium , Interfascicular cambium ,

secondary xylem , secondary phloem

Definition :annual ring , early wood , late wood ,

sap wood , heart wood , rhytidome

1.Epidermis

2.Periderm

①phellem phellogen②phelloderm③

3.Cortex

4.Phloem fibre

5.Vascular bundle

①phloem cambium②

③xylem

6.pith

transverse section

radial ～ tangential～

Ⅰ.transverse section Ⅱ.radial section

Ⅲ.tangential section4.Secondary xylem

5.ray6.Annual ring7.Sap wood

8.Heart wood

Early wood

and

late wood

Sap wood and

Heart wood

B. Herbaceous Dicot Stems

The model sketch of herbaceous stem

1.non-glandular hair

2.Glandular scale

3.Collenchyma

4.Epidermis

5. glandular hair

6.Endodermis

7.Fibre

8.Phloem

9.stone cell

10.xylem

The detail drawing of herbaceous stem

c. Rhizome of Dicot Stems

一、 Normal Structure of RhizomaTransverse section of huanglian rhizom

a

1 、 phellem

2 、 cortex

3 、 stone cell group

4 、 5 、 rays

6 、 phloem

7 、 xylem

8 、 pith

Transverse section of the rhizome

of Huanglian

1.cork

2.cortex

3.Stone cells

4.Pericyclic fibre bundles

5.cambium

6.phloem

7.Pith ray

8.xylem

9.pith

二、 Anomalous Structure of Rhizome of Dicot Stems

（ 1 ） Anomalous structure of rhubarb rhizoma

Up， 1、 phloem

2、 cambium

3、 xylem rays

4、 star dots

Down， 1、 vessel

2、 cambium

3、 phloem

4、 grume cavity

5、 rays

Transverse section of rhizome

of Dahuang

1.xylem

2.pith

3.Allotype vascular bundle

（ 2 ） Transverse section of Mihuadou stems

（ 3 ） Transverse section of spikenard Rhizoma

1 、 phellem

2 、 phloem

3 、 xylem

4 、 pith

5 、 cranny

④Structure of Monocot Stems

①Without cambium and phellogen

②Closed collateral vascular bundle or amphivasal b

undle

③No pith endodermis

Transeverse section of stem of Monocot and Dicot

⑤Gymnosperm Stems

Like Woody Dicot Stems , but different parts is that

it has tracheid ,rays , xylem parenchyma without x

ylem fiber. Meanwhile secondary phloem is simple.

Transverse Section of Gymnosperm

1、 epidermis 2、 phellem

3、 phellogen

4、 cortex basic meristem

5、 epithelia 6、 phloem

7、 cambium 8、 xylem rays

9、 resin canal

10、 secondary xylem

11、 pith rays

12、metaxylem

13、 protoxylem

14、 pith

Review Questions一 .Definition node , internode , exarch , endarch , annual

ring , early wood , late wood , sap wood , heart wood

二 .simple answer 1.what is the difference of the stem of Mono

cotyledoneae and Dicotyledoneae? 2.what is the function of the stem? 3.How about the secondary structure of the

woody stem?