BIOL-2356EL Lecture 6: BIOL 2356 Lecture 6
27 Sep 2018
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Document Summary
Photosynthesizing plants face an important ecological dilemma: uptake of co2 is associated with loss of water. Photosynthesis: synthesis of carbohydrates from co2 by green plants using sunlight. Transpiration: loss of water vapour from plants, mostly via stomata. Evaporation: loss of water vapour, usually from soil surface. Respiration: using organic matter as a source of energy (atp) by all organisms, mostly upon release of co2. When there is light, temperatures are high and water evaporates easily. Water loss through transpiration is high if stomata are open. Cam plants open their stomata and assimilate co2 at night. At night air is humid: reduced water loss. However, photosynthesis can only happen in daylight: temporal separation of energy capture and initial carbon assimilation. During night they take in co2 and during the day they fix it to sugar. During the day the stomata is closed so they don"t loose water. Cam plants are often succulent: large vacuole to store malate.
