Transpiration Flashcards
define osmosis
movement of water from low solute concentration across a selectively permeable membrane
define transpiration
the loss of water through leaves by evaporation through the stomata
what are adaptations of a root hair cell
-large surface area because it has a long projection, to allow for efficient absorption of water osmosis and minerals via active transport
what’s the transpiration pull
evaporation of water from the mesophyll cells pulls other water molecules from the xylem tissue
how does water enter the root cortex
-soil has a higher water potential than inside a root hair cell
-water enters the root hair cell by osmosis
-water moves out of the root hair cell to the root cortex
-water continues, so a water potential gradient is set up across the root cortex
what is the purpose of transpiration
-supplies water for leaf cells
-carries mineral ions
-provides water to keep plant cells turgid
-allows evaporation from leaf (cools it
why doesn’t water pass out from the top of the leaf
there is a waxy cuticle on the top of the leaf which prevents water loss in that direction
how does water exit the leaf
-water leaves the spongy mesophyll cells and evaporates into the air spaces of the spongy mesophyll layer where the water potential is lower,
-then continues to move down the concentration gradient out of stomata.
-This sets up a transpiration stream as water is ‘pulled up’ the xylem and moves down the concentration gradient to replace lost water further up the plant
what do plants need to stay alive
-sugars, minerals and water to stay alive
which way does water and sugar go through the plant
water goes up, and sugar goes down the plant
what does gas exchange do
allows oxygen from photosynthesis to be released into the atmosphere and CO2 from respiration to be released through diffusion
why do plants need transport systems
-they are multicellular
-surface area to volume; diffusion alone is insufficient to supply resources
what does the xylem do
-transports water and minerals
-dead cells arranged end-end
-vessels have no cytoplasm, just a lumen
-xylem walls contain woody materials(lignin) that is very strong and impermeable to water
what does the phloem do
-transports products of photosynthesis from leaves to other parts of the plant(regions of storage or utilisation)
-sucrose, amino acids are transported
-living cells are arranged end-end
-end of each cell is a wall of cellulose with holes(sieve plates)
-cytoplasm extended through holes in sieve plants and link each cell with the next
-cells have no nucleus - controlled by companion cells that lie next to the tube
how are plants adapted to reduce excessive water loss
-thick leave(reduces Surface area : volume
-thick waxy cuticle
-stomata concentrated on underside of leaves
-hairs on leaves trap moist layer for longer to reduce concentration gradient
-curled leave to trap moist layer of air (stomata sunken in close stomata at day)
