Water in Plants Flashcards
diffusion
molecules of any substance have the tendancy to spread out evenly to the available space; occurs along concentration gradient
turgor pressure
happens when the solute concentration in them is higher than that outside
transpiration
water vapor/droplets given off in leaves of plant
tension cohesion model
water is pulled up the plant; transpiration in leaves create tension; tension extends from leaves to stems to roots; tension draws up water; soil-root-root xylem-stem xylem-leaf mesophyll-atmosphere
osmosis
water moving into or out of a plant cell
pressure flow hypothesis
water is pushed up the plant; water moves into the root tissues by osmosis; explain water transport in spring when soil is wet; does not explain large plants in hot summers; explains sugar translocation
plasmolysis
occurs when solute concentration in a plant cell is lower than that outside;
root pressure model
food is converted into sucrose before translocation; sucrose in the phloem moves from a source (leaf) to sink (root/fruit)
sink
root cell; connected to a companion cell; root/fruit
source
leaf
What is NOT part of the transpiration-cohesion-tension mechanism for the ascent of xylem sap?
the diffusion of water into the xylem of roots
In the pressure flow hypothesis of translocation what causes the pressure?
the accumulation of minerals and water in the root xylem
What is the main force by which most of the water within xylem vessel moves toward the top of a tree?
the evaporation of water through stoma
Plants require water for…
enzyme and chemical activity; cell content; photosynthesis
All of the following describe an important component of the long distance transport process except…
pressure flow from source to sink
