Transport in plants

(d, f, g, i, j)

* define the term transpiration 

* describe the factors that affect transpiration rate

* describe how a potometer is used to estimate transpiration rates

*  describe, with the aid of diagrams, the pathway by which water is transported from the root cortex to the air surrounding the leaves, with reference to the casparian strip, apoplast, symplast and vacuolar pathways, xylem and stomata

* explain the mechanism by which water is transported from the root cortex to the air surrounding the leaves, with reference to cohesion, adhesion and the transpiration stream.

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  • Created by: EClou
  • Created on: 02-04-15 18:25
what is cohesion?
the attraction of water molecules for one another
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What is adhesion?
the attraction of water molecules of the walls of the xylem
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where are root hair cells located?
the epidermis of plant roots
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how do roots absorb water?
root hair cells absorb minerals for the soil particles by active transport, this lowers the WP of the cytoplasm so water is taken in across the plasma membrane by osmosis.
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what is the casparian strip and what is its function?
a waterproof strip found in the cell walls of the endodermis,
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what three processes help water move up the stem?
1. root pressure, 2. transpiration pull, 3. capillary action
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what is the cohesion-tension theory?
the idea that as water that evaporates from the leaf is replaced by the xylem, tension is created and maintained by the cohesion between water molecules in the column of the xylem.
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define transpiration
the loss of water by evaporation from the aerial parts of a plant.
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what is the transpiration stream?
water leaving in the leaf must be replaced from below, therefore water moves up the xylem from the roots.
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give three ways in which the transpiration stream is useful.
1. water is required in the leaves for photosynthesis, 2. water maintains turgidity, 3. the flow of water can carry useful minerals up the plant.
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what three processes does transpiration involve?
1. osmosis from xylem to mesophyll, 2. evaporation from mesophyll surface to to intercellular spaces, 3. diffusion of water vapour from intercellular spaces through the stomata.
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why are the stomata open during the day?
to allow gaseous exchange for photosynthesis.
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what is a potometer used for?
estimating the rate of water loss.
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what are the three errors of the potometer experiment?
1. water is used in photosynthesis, 2. water used in vacuoles to maintain/return turgidity in wilted shoot, 3. extra water may be produced by respiration.
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what three things must you check before starting the potometer experiment?
1. there are no air bubbles anywhere in the apparatus, 2. the shoot you have selected has not wilted, 3. the apparatus it air/water tight
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give three environmental factors that affect the rate of transpiration:
1. wind, 2. relative humidity, 3. light.
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give three physical factors that affect the rate of transpiration:
1. thick waxy cuticle - impermeable, 2. stomata in pits - trap water vapour, 3. hairy leaves - trap water vapour
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what happens if too much water is lost from a plant?
plant cells will lose turgidity, non-woody plants will wilt and eventually die, and woody plants' leaves will wilt, so the plant will eventually die.
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give three functions of the casparian strip
it blocks the apoplast pathway forcing water into the symplast pathway so that the minerals pass through the cytoplasm.
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2
once water has entered the xylem, it cannot pass back into the cortex
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3
nitrate ions are actively transported from the cytoplasm of the cortex to the xylem by active transport
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Other cards in this set

Card 2

Front

What is adhesion?

Back

the attraction of water molecules of the walls of the xylem

Card 3

Front

where are root hair cells located?

Back

Preview of the front of card 3

Card 4

Front

how do roots absorb water?

Back

Preview of the front of card 4

Card 5

Front

what is the casparian strip and what is its function?

Back

Preview of the front of card 5
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