Reagent in biochemical reactions and transport medium
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Describe the water uptake by roots
Water is drawn up the xylem by the transpiration stream to replace water loss at the leaves. Water crosses the membrane and cytoplasm of the cells. Water crosses living cells of cortex by suction. Water enters toots by osmosis.
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How are root hair cells adapted to their function?
They have a large surface area, they have no chloroplasts and a large vacuole
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What does the xylem transport?
Water and minerals
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How does the xylem move?
Up the stem
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xylem gives the plant...
mechanical support
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In the vascular bundle, xylem is in the...
Middle
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The cells in xylems have no...
Cell content
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Xylem tissue is strong because...
of the presence of lignin
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What does the phloem transport?
Food and nutrients
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How does the phloem move?
Up and down
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Where is phloem in the vascular bundle?
Outside
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What does the cortex do?
It acts as a winter store for starch
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Define transpiration
Loss of water vapor from plant leaves by evaporation of water at the surface of the spongy mesophyll cells followed by the diffusion of water vapour through the stomata
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Why does wilting occur?
Water loss exceeds water uptake, cells become flaccid and tissue become limp.
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Why can't water vapor diffuse into the leaf?
Because the spaces between the spongy mesophyll cels are saturated
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Define a transpiration stream
The flow of water through the plant to replace the water loses by evaporation from the leaf
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Which atmospheric conditions affect transpiration?
Wind, high temperature, low humidity and high light intensity
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Why does transpiration increase if the wind blows?
Water vapor is moved away from the leaves, increasing water potential gradient between the leaf and the atmosphere
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Why does high temperature increase transpiration?
It increases the water holding capacity of air
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How does low humidity increase the rate of transpiration?
It increases the water potential gradient between the leaf and the atmosphere
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How does high light intensity increase the rate of transpiration?
More photosynthesis occurs
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How can leaf structure reduce transpiration?
Waxy cuticle may be thick, stomata may be sunk into pits, leaves may be rolled up with stomata on the inner surface, leaves may be turned into needles
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Define translocation
Movement of sucrose and amino acids in the phloem from sources to sink or vice versa
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How are cacti (xerophytes) adapted to reduce water loss?
Their stem photosynthesizes, their leaves are reduced to spines, their stomata are sunk into grooves, their stem stories water, they have an extensive root system
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How are aquatic/pond plants adapted to reduce water loss?
Their stomata are at the upper side of the leaf, they have a thin cuticle, there is little lignin in the xylem
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Why do aquatic plants have little lignin in the xylem?
Because they are supported by water
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Other cards in this set
Card 2
Front
Describe the water uptake by roots
Back
Water is drawn up the xylem by the transpiration stream to replace water loss at the leaves. Water crosses the membrane and cytoplasm of the cells. Water crosses living cells of cortex by suction. Water enters toots by osmosis.
Card 3
Front
How are root hair cells adapted to their function?
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