· Plants need water for... -photosynthesis -a medium to carry out chemical reactions -to keep cells firm for functioning, and prevent wilting*Water comprises 70-95% of a plant's weight· Two ways of losing heat -Convection: only occurs if the temperature of a leaf is higher than its surroundings. -Evaporation: ~Water from leaf surface withdraws heat from a plant because energy is absorbed by water -can occur even if the temperature of the leaf is below that of the surrounding air*A typical leaf dissipates about 50% heat by evaporation, 50% by convection -Plants with a bias to convective heat loss: xenophytes ~thick fleshy tissues in which water is stored -Plants with a bias to evaporation: ~good at uptaking water and transporting water · Water uptake by root -rhizosphere (读作[raizosphere]): the volume of soil as
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