13. Uptake and Movement of Water Flashcards
water moves from ____ water potential to ___ water potential
high ; low
water moves from areas of ___ solute concentration to areas of ___ solute concentration
low ; high
water moves from more ___ water to more ___ water
pure ; diluted
the highest water potential is a value of ___ which is the water potential of ___ water
0 ; pure
water moves by 2 forces:
diffusion and bulk flow
water moves via diffusion in these places:
entering root tips
leaving leaves
water moves via bulk flow in this place:
xylem
when water enters roots, there are two pathways:
apoplast and symplast
the apoplast root pathway
water and nutrients flow through cell walls and intercellular spaces (abiotic), eventually is blocked by casparian strip
the symplast root pathway
water and nutrients flow through cell membranes and plasmodesmata (connecting cells), this is the biotic pathway
the casparian strip
blocks the abiotic/apoplast pathway into the root, forces everything that enters a plant via roots to pass through a membrane
gymnosperm xylem
tracheids, perforations of complex put membrane
angiosperm xylem
use vessel elements, wide and short, perforated by simple pit membranes
secondary xylem is laid down by:
vascular cambium
secondary xylem is also called:
wood
secondary walls of xylem are made of:
cellulose and lignin
lignin: non-carb polymer that binds the cells fibers and vessels, water impermeable
essentially, glucose bound in fiber bundles, glued together with lignin
why do secondary xylem need to be so strong?
they withstand a lot of negative pressure from the difference in water potential at the leaves vs the roots
transpiration pull
the transpiration of water from leaves causes water to move up xylem, the negative pressure at the leaves causes a tension = pulling force
