materials including mineral ions, sugars & hormones are moved around the leaf dissolved in water. this is carried up the plant via a transpiration pull.
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what are the factors affecting transpiration?
light, temperature, humidity, air movemen (wind)
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how does light affect transpiration?
stomata open for CO2 to enter for photosynthesis. when in light the stomata is open allowing for water to be lossed. in the dark they are shut.
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how does temperature affect transpiration?
rise in temp increases kinetic enrgy of water molecules increasing the rate of evaporation. it also dcreases the air outside the leaf decreasing the water potential.
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how does humidity affect transpiration?
it affects the water potential gradient between leaf and air. when the outside has high humidity the gradient is reduced and rate of transpiration is lower.
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how does air movement affect transpiration?
vapour is collected around stomata. this increase water potential around the stomata reducing transpiration rate. however, the wind disperses the vapour decreasing water potential of air increasinf the rate of transpiration.
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what are xeropytic plants?
plants that do not have a good supply of water developing adaptations to limit water loss.
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what are the adaptations xerophytes develop?
thick cuticle- waterproof layer so less water can escape. rolling up of leaves- protecting lower epidermis and stomata trapping still air so there is no water potential gradient. hairly leaves- traps moist air on leaf surface reducing water potential
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what are the adaptations xerophytes develop? cont.
stomata in pits or grooves- traps moist air next to leaf reducing water potential. reduced surface are to volume ratio- smaller surface area the slower the rate of diffusion.
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what makes root hair cells good for water exchange?
large surface are & short diffusion pathway being thin.
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why and how does water move into the root hairs?
due to the soil having a high water potential compared to root hair so water moves into roots via osmosis.
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what are the 2 pathways for water absorption??
symplastic and apoplastic
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where in the cell does water move in the apoplastic pathway and why?
they move along the cell wall due to the cohesive preoperties and tension caused by water molecules.
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where in the cell does water move in the symplastic pathway and why?
move across the cytoplasm via osmosis.
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how does water move through cells in the symplastic pathway?
through plasmodesma. each following cells also has a lower water potential causing water to moves in through a water potential gradient
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how does wate move into the xylem?
when the water reaches the casparian ***** water is forced into the protoplast. this is due to a water potential gradient caused by the active transport of the salts and minerals causing water to diffuse via osmosis.
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