movement of water into plants Flashcards
(23 cards)
why is water potential in a plant always negative
-the cytoplasm contains mineral ions and sugars that will lower the water potential
why do plant cells in pure water take in water by osmosis
-the water potential in the cell is lower than the water
why do plant cells in pure water not burst
-there is an opposing pressure from the strong cellulose cell wall
-as pressure builds, reduces influx of water
what happens during water uptake
-cell becomes turgid
-water inside exerts pressure on wall (pressure potential)
-as pressure builds, reduce influx of water
what is the pressure potential
water inside cell exerts pressure on cell wall
what happens during water loss
-cytoplasm and vacuole shrink
-cytoplasm no longer exerts pressure on cell wall
-plasmolysis of cell
-tissue = flaccid
what are the 3 paths that water can take
-symplast
-vacuolar
-apoplast
what is the apoplast pathway
-water passing through the spaces in the cell walls and between cells
-doesnt pass through any plasma membranes
-dissolved mineral ions and salts can be carried
what does water in the apoplast pathway move via
-mass flow
-not osmosis as it doesnt pass through a membrane
what is the symplast pathway
-water enter cell cytoplasm through plasma membrane
-passes through plasmodesmata from one cell to the next
what is the vacuolar pathway
-similar to symplast
-except water isnt confined to the cytoplasm of cells
-able to enter and pass through vacuoles too
what is the water potential
the measure of the tendancy of water molecules to diffuse from one region to another
what is osmosis
-the passage of water molecules
-down their potential gradient
-across a partially permeable membrane
what is turgid
-swollen state of plant cells that have taken in water by osmosis
-reached max state of swelling
-cell wall exerts pressure to prevent any more water entering cell
whats flaccid
-when tissue is soft
-no longer turgor
what is plasmolysis
-content of cell shrunk due to loss of water by osmosis
-plasma membrane separated from cell wall
how does water move from cell to cell
-when plant cells touch water molecules move from less negative to more negative water potential
how does water get into xylem from cortex
-at the point in which endodermis seperates root cortex from stele
-apoplast pathway is blocked by coating of suberin (casparian strip)
-casparian strip gives plant more control over what enters xylem
what is the stele also known as and what is it
the medulla
-central core of vascular tissue in a plant root or stem
what is the casparian strip
-a coating of suberin (fat)
-gives plant more control over what enters xylem as it forces water to go through cell membrane of endodermal cells which is selectively permeable
why does the casparian strip give plants more control over what enters xylem
- it forces water to go through cell membrane of endodermal cells which is selectively permeable
what is the cortex of the cell
- region of parenchyma tissue located between the epidermis (outer layer) and the vascular tissue
how is osmosis encouraged into the medulla and xylem
-mineral ions actively transported into medulla
-making water potential more negative
-so water follows by osmosis
