water transport pathways

Question 1

define water potential as a mechanism of movement in plants

Answer 1

• water potential = the tendency of water to move by osmosis, from a high to low water potential
• pure distilled water has the highest water potential of 0 (everything else will be negative)
• this is the basis by which water moves to the areas it is needed within plants

Question 2

explain what is meant by apoplastic pathway

Answer 2

• a method of osmosis through the root hair cells, where water moves through the cell walls and intercellular spaces
• this pathway can only be used until water reaches the Casparian strip
• cohesion and tension forces pull the water up
• fastest movement as minimal resistance

Question 3

what is meant by the symplastic pathway

Answer 3

• a method of osmosis through the root hair cells, where water moves through the cytoplasm via plasmodesmata (connecting cytoplasmic links)
• to begin this pathway, water must be actively transported into cells

Question 4

explain the cohesion-tension theory

Answer 4

water molecules form hydrogen bonds with each other, causing them to stick together. the surface tension of the water also creates this sticking effect. therefore as water is lost through transpiration, more can be drawn up the stem from the roots