PLANT SYSTEMS QUESTION 1988:		L. PETERSON/AP BIOLOGY

	Trace the pathway in a flowering plant as the water moves from the soil 
	through the tissues of the root, stem, and leaves to the atmosphere. Explain
	the mechanisms involved in conducting water through these tissues.



STANDARDS:		

 ANATOMY AND PATHWAY:				Max. = 6 points

__  Pathway....some relationship from root to leaf required for a 10
       mention of "root tissue -> transport tissue -> leaf tissue
	       e.g.  root hair -> xylem -> stomata

Max. 5 - Anatomy of Pathway
__  Soil water or capillary water
__  Root hairs or Epidermis
__  Cortex or Parenchyma
__  Plasmodesmata
__  Endodermis
__  Pericycle
__  Procambium
__  Xylem or Vessels or Tracheids or Vascular Bundle
__  Petioles
__  Mesophyll Cells or Leaf Parenchyma
__  Intercellular Spaces
__  Stomata or Guard Cells

Max. 2 - Additional Points
__  Symplastic - water moves through protoplasts, plasmodesmata
__  Apoplastic - water moves along cell walls
__  Elaboration of Sylem - e.g. dead cells, hollow cells, main water transport
__  Casparian Strip - involvement in directional or selective flow
__  10% of water through the cuticle

MECHANISMS OF WATER MOVEMENT:		Max. = 6 points
	Explanation of Mechanism = 1 point / Name alone = 0 point
__  Osmosis - diffusion of water through semipermeable membrane
__  Transpiration - evaporation of water from leaf
__  Cohesion - water forms chain through H bonding, molecules adhere to each other
__  Adhesion - water adheres to cell walls, unlike molecules attract
__  Root Pressure - water enters root due to solute accumulating in root cells, force
         exerted by root cells on water column
__  Water potential - negative pressure in leaves; positive pressure in roots;
	           	flow is along gradient of decreasing water potential

Max. 2 - Additional Points
__  Root hairs - large surface area -> absorption
__  Stomatal mechanism - open stomates allow transpiration/how guard cells act to 
         regulate flow
__  Stomate placement relative to rate of transpiration, effect on transpiration
__  Root pressure - requires an energy dependent mineral movement into xylem
__  Guttation (proof of root pressure)
__  Elaboration of water potential relative to cohesion and adhesion