9700 · 14.2
Homeostasis in plants flashcards
Revision flashcards for Cambridge 9700 Homeostasis in plants (syllabus 14.2). Flip, recall, then mark a real past-paper question.
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Why must plants maintain homeostasis?
To keep enzyme-catalysed reactions (e.g. photosynthesis) at optimal rates despite environmental change.
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What triggers stomatal closure in drought?
Abscisic acid (ABA) from roots when soil water is low; causes $K^+$ efflux from guard cells.
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How does light affect guard cells?
Light stimulates $K^+$ uptake, water entry by osmosis, turgidity, and stomatal opening.
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What is a xerophytic adaptation?
Structural or physiological feature reducing water loss in arid conditions (e.g. sunken stomata, thick cuticle).
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Role of the Casparian strip?
Suberin deposit in endodermis forcing water into symplastic pathway for selective mineral uptake.
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Turgor pressure in plants?
Pressure of cell contents against the cell wall when water enters by osmosis; maintains rigidity.
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Why close stomata at night?
Photosynthesis cannot occur without light; closure reduces unnecessary transpiration.
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How does high $CO_2$ affect stomata?
High internal $CO_2$ signals reduced need for uptake, promoting stomatal closure.