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

Herba Ephedrae Cortex Eucommiae Medulla TetrapanacisLignum 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  ① upper 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 stem 1.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）

 ② Subterraneous stem  Rhizome  Tuber  Corm  bulb

abnormal subterraneous stem Ⅰ.rhizome Ⅱ.rhizome Ⅲ.tuber Ⅳ.corm Ⅴ.bulb 1.scaly leaf 2.terminal bud 3.bulb plate 4.adventitious root Ⅵ. bulb

The abnormal subterraneous stem 1.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 Stem  ① Structure of Stem Apex  meristematic zone  elongation zone  maturation zone

 ② Primary Structure of Dicot Stems  epidermis （ trichome and stoma ）  cortex  vascular cylinder Definition :  endarch:  The order of differentiation and maturation of primary xylem of stem is from the inside to outside, and is known as endarch.

Primary structure of Dicot stems 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

③ Secondary Structure of Dicot Stems A. 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 ① phellem ② phellogen ③ phelloderm 3.Cortex 4.Phloem fibre 5.Vascular bundle ① phloem ② cambium ③ xylem 6.pith

transverse section radial ～ tangential ～

Ⅰ.transverse section Ⅱ.radial section Ⅲ.tangential section 4.Secondary xylem 5.ray 6.Annual ring 7.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 Rhizoma Transverse section of huanglian rhizoma 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

④ Structure of Monocot Stems  ① Without cambium and phellogen  ② Closed collateral vascular bundle or amphivasal bundle  ③ No pith endodermis

Transeverse section of stem of Monocot and Dicot

⑤ Gymnosperm Stems  Like Woody Dicot Stems, but different parts is that it has tracheid,rays, xylem parenchyma without xylem 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 Monocotyledoneae and Dicotyledoneae?  2.what is the function of the stem?  3.How about the secondary structure of the woody stem?