Hachi's posts

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Stomatal density is under both genetic (natural selection) and environmental (plastic) control

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Waxy cuticle prevents water loss from other parts of the leaf

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Amount of water lost depends on number of stomata and their pore size

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Stomata - main avenue of water loss. Flanked by a pair of guard cells that change shape to widen or narrow the gap

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Stomatal guard cells help balance a plant’s requirement to conserve water and perform photosynthesis

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Larger internal SA due to honeycomb of air spaces (spongy mesophyll)

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Leaves - large SA enhances light absorption, high surface-to-volume ratio aids in gas exchange

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No energy required - sunlight drives transpiration and lowers water potential in leaf air spaces

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Entire solution moves together (not just water or solutes)

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Flow doesn’t occur across plasma membranes of living cells - instead, within hollow, dead cells

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Bulk flow is driven by differences in ѰP (ѰS is not a factor) → water potential gradient in xylem is a pressure gradient

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Bulk flow in xylem vs. diffusion in plant cells

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Secondary growth adds new xylem each year (only youngest secondary xylem transports water)

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Root pressure (positive) can refill the blocked vessel elements