Morphology of Stems

Introduction to Stems and External Features 
·         Stem is the axis of the plant other than the root

·         In most plants stems are located above the soil surface but some plants have underground stems

·         Functions of the stem

§  Stems support the leaves and other structures e.g. flowers, fruits 

§  Stems are used for vegetative reproductive i.e. cuttings

§  Stems position leaves to receive maximum sunlight

§  Stems determine size and shape of the plant

§  Facilitates movement of water, minerals, and manufactured food in the plant

§  Some stems carry out photosynthesis

§  Stores foods

·        External features of the stem

·         External structures of the stem

§  Internodes: distances separating one node from another

§  Nodes: Points at which leaves are attached

§  Lenticels: Breathing pores

§  Buds:Growth of shoot

§  Terminal or apical but, at tip of plant

§  Axillary bud in nodes on stem

§  Bud scale scars: Indicate where terminal bud has been located previous year

§  Leaf scars:

§  Show where leaf was attached

·          Internal structures of the stem

§  Usually consist of three tissues, Dermal tissue, Ground tissue and Vascular tissue

§  The dermal tissue

§  Covers outer surface of stem and usually functions to waterproof, protect & control gas exchange

§  The Ground tissue

§  Mainly of parenchyma cells and fills in around the vascular tissue, sometimes functions in photosynthesis

§  The Vascular tissue

§  Provides long distance transport and structural support

§  Arrangement varies widely among plant species

Selective Focus Photography of Green Leaf on Branch With Snow

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