The Stem

water from this willlow's roots must travel upward.sideways, and downward through its stems to reach the most distant leaves. Food produced by the outermost leaves travel up, across, and down to reach the roots.

ROLE

• brown, rigid stems= long life span for plant

• vascular bundles in monocots are scattered throughout the stem cross section

• vascular bundles in dicots are gathered together in orderly rings
  
• supports and gives nutrition to the plant

• holds plant's leaves up to the sun

FUNCTION

1. water + dissolved mineral nutrients are transported from the roots to the leaves ( performed by the xylem)
   
2. newly manufactured food molecules are transported from the leaves to the roots for storage ( performed by the phloem)
   
3. food stored in the root is transported to any plant part that needs it ( performed by the phloem)
   

SECONDARY STRUCTURES

Stolons

• above-ground horizontal stems

• produce new plants where the nodes in the stem touch the ground

Rhizomes

• underground, horizontal stems
  
• have long and thin stems or thick and fleshy stems
  


• reproduces asexually= node of the stems has a bud
  
• have enlarged sections called tubers

Corms

• a short, thickened, underground, upright stem where food is stored

EPIDERMIS
ROLE

• layer of cells that protect the inner tissues

SECONDARY STRUCTURES

• covered by a cuticle

• stomata allows gases to enter and exit
  
• contains chloroplasts to perform photosynthesis
  

CORTEX AND PITH

ROLE & FUNCTION

• region of ground tissue between the epidermis and the vascular bundles is the stem cortex; the region of ground tissue in the center of the stem is the pith

• cortex= cells are irregular in shape and arrangement

• pith= cells walls are thin and there are more air spaces among the cells

• cortex stores food in the form of starch

• pith stores water and small amounts of food
  
• the cortex and the pith don't transport food and water
  

SECONDARY STRUCTURES

• turgor helps keep stems straight