What part of the plant determines how much water is exchanged with the atmosphere?
The leaves (the stomata)
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What are stomata?
Variable valves covering leaf and stem, facilitating gas exchange of CO2 and water
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What are guard cells?
The cells around the stomatal opening which control the opening and closing
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Where are stomata found?
Tops (and sometimes bottom) and stem
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What is it called when a plant has stomata on both the upper and lower side of the leaf?
Amphistomatous
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What is it called when a plant only has stomata on the lower surface?
Hypostomatous
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What affects the size, distribution and frequency of stomata?
Genotype, leaf position and growth conditions
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Name some environmental stimuli which stomata are responsive to
Light, heat, humidity (inside and outside cell), CO2, air pressure, touch
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What is the diffuse capacity of the leaves?
The product of stomatal number and stomatal aperture
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Describe the stomatal conductance
The modern method, shows amount of water lost per square meter per second (mol H20 m-2 s-1)
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What does the stomatal conductance show?
The higher the stomatal conductance, the more stomata are open
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Describe reciprocal of conductance
Used before we could measure water loss, also known as stomatal resistance (cm s-1)
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What does the reciprocal of conductance show?
The higher the stomatal resistance, the more closed stomata
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How does potassium ions in the leaves affect the plant?
the higher the concentration, the more water is taken up as the concentration gradient increases inside the cell
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Explain how guard cells control the opening and closing of the stomatal aperture
Water increase, higher turgor pressure in guard cells, microfibrils in guard cells allow them to expand and so they buckle, increasing size of opening between the adjacent walls
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What does the opening and closing of stomata throughout a day show?
Endogenous circadian rhythm
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What happens when the roots detect drying soil?
Abscisic acid is generated in root tips, passes up the xylem and to the stomata, signalling them to close
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Other cards in this set
Card 2
Front
What are stomata?
Back
Variable valves covering leaf and stem, facilitating gas exchange of CO2 and water
Card 3
Front
What are guard cells?
Back
Card 4
Front
Where are stomata found?
Back
Card 5
Front
What is it called when a plant has stomata on both the upper and lower side of the leaf?
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