Stem

• Stem - Main axis of the plant that bears all structures located above the ground.

  Structure: alternating system of nodes and internodes.

  Function: highway for the  conduction of water, minerals, salts, and  manufactured food; bear and support the leaves, flowers, and fruits.
• Parts of a stem:

  Node – attachment site of petiole

  Internode  –  segments  between

  nodes

  Leaf scar – mark left by a fallen leaf

  Lenticels – tiny pores on stems

  Buds – underdeveloped structures that may grow into leaves, shoots, or flowers

  • Terminal, lateral, accessory, adventitious
  • Protected, naked
  • Vegetative, flower, mixed

  Bundle scars  – cut ends of vascular bundles
• Twig Parts

  A) terminal (apical) bud

  B) stipule scar

  C) lateral (axillary bud)

  D) node

  E) lenticels

  F) internode

  G) leaf scar

  H) vascular bundle scars

  I) terminal bud scale scars

  
• Types of stems:

  Underground stems

  • Bulb – flattened and consist of short, disc-like stems enclosed in
  • overlapping layers of fleshy leaves
  • Corm – vertical thick stems that have thin, papery leaves
  • Rhizome – stems that grow horizontally below the ground
  • Stem tuber – swollen ends of the underground lateral stems

  Aerial stems

  According to texture:

  • Herbaceous
  • Woody / arborescent
  • Suffrutescent

  According to direction of growth:

  • Erect
  • Ascending / assurgent
  • Decumbent
  • Prostate / procumbent
  • Creeping / repent
  • Climbing
• Parts of a Stem

  A) Node

  B) Internode

  C) Bud

  D) Bud

  
• Underground Stems

  A) bulb

  B) corm

  C) rhizome

  
• Aerial Stems

  A) arborescent

  B) suffrutescent

  C) prostrate

  D) decumbent

  E) repent

  
• Stem Modifications

  A) caudex

  B) cladodes

  C) scape

  D) stolon

  E) culm

  
• Stem modifications

  • Boles - unbranched stems of forest trees
  • Caudex - unbranched woody stems
  • Culm - hollow or solid stems
  • Stolons/runners - stems that lie flat on the ground
  • Scrape - leafless flowering stem
  • Cladophyll - resembles a leaf in form and appearance