transport in plants Flashcards
adaption of root hair cell
-long narrow tubular extension which increases SA:V for absorption
-high concentration of salts, amino acids and sugars in cell sap of root hair cell for a low water potential so water can diffuse into it through osmosis
-large vacuole to take in water
-mitochondria to release energy for active transport of mineral salt ions
function and adaptation of xylem
-conducts water and mineral ions from soil to stem and leaves
-provides mechanical support, prevents the collapse of xylem vessels
-xylem cells have on protoplasm to reduce the resistance to water flowing through it
-walls are thickened with lignin which is a hard and rigid substance that prevents the collapse of the vessel
function and adaptation of phloem
-move organic solutes through leaves to whole plant
-companion cells have many mitochondria which provides the energy needed for companion cells to load sugar from mesophyll cells into the sieve tube through active transport
-holes in the sieve plates allow rapid flow of manufactured food substances through the sieve tube cells
what are sieve tube and companion cells
sieve tube cells are living cells with no nucleus or vacuole, thin cytoplasm, sieve plates
-companion cells have cytoplasm, nucleus and mitochondria that provides sieve tube cells to the sieve tube cells, helps transport food by active transport
describe translocation
-loading of sugar into the sieve tube at the source, reducing the relative water potential in the sieve tube members causing osmosis from surrounding cells
-uptake of water causes a positive pressure that results in a flow
-this pressure is diminished by the removal of sugar from sieve tube at sink, which is changed to starch which is insoluble and does not exert osmotic pressure
-xylem recycles relatively pure water by carrying it back from the sink to the source
describe root pressure
-cells that surround the xylem vessels actively pump mineral ions into the xylem vessels
-water potential in the xylem vessel decreases, creating a water potential gradient
-water moves in by osmosis from these cells into xylem vessels, as water continues to enter the xylem, increasing pressure pushes the water column upwards but is unable to bring water all the way up
what is capillary action
-spontaneous movement of water along narrow tubes contributing to upwards movement of water in small plants
-force of attraction between water molecules, and FoA between water molecules and inner surface of capillary tube
define and describe transpiration pull
-the loss of water vapour from aerial parts of the plant, especially through stomata of the leaves
-as water leaves the mesophyll cells, a tension is created
-cohesion of water molecules and adhesion of water molecules to xylem wall causes water to move upwards
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describe the movement of water inside a leaf
-water continuously moves out of mesophyll cells creating a thin film of moisture over their surfaces
-water evaporates from thin film of moisture and moves into intercellular air spaces, water vapour accumulates in large air spaces near stomata
-water vapour diffuses through the stomata to the drier air outside the leaf
-as water from mesophyll cell diffuses out, water potential of cell sap decreases, begin absorbing water from cells deeper inside the leaf, cells in turn remove water from xylem vessels
-results in suction force that pulls column of water up the xylem vessel
describe the effects of humidity, wind, temperature and light on transpiration
-higher humidity, lower evaporation water from leaf due to decreased concentration gradient, slower rate
-higher wind speed, maintain concentration gradient as it blows water vapour away from leaf, higher evaporation, higher rate
-higher temperature, higher rate of evaporation, higher rate
-sunlight, stomata opens increasing rate of transpiration
how does wilting occur
Wilting occurs when plants lose more water through transpiration than they can absorb from the soil, causing their cells to lose turgor pressure and the plant to droop.
