BIO130H1 Lecture Notes - Lecture 4: Stoma, Hemiepiphyte, Cactus
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BIO130H1 Full Course Notes
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Lecture 4: physical challenges for terrestrial plants, emphasis on tradeoffs and alternative lifestyles. Tradeoffs on photosynthesis: compromises with light, temperature and water. Mostly evergreen, lasting several seasons e. g. hardwood trees such as maples, oaks. Mostly evergreen, lasting several seasons e. g. hardwood trees such as maples, oaks e. g. some coniferous trees such as pines, firs and spruces. Large leaf surface area = good for light harvesting and carbon dioxide consumption, but bad for overheating and water loss by evapotranspiration via stomata. Combat overheating by growing in shady habitats and evaporative cooling via stomata. Combat water loss by closing stomata, but risks no photosynthesis and overheating. There must be a tradeoff between water conservation and rapid growth. It can grow without incurring heat load and water loss via leaves. Small sa: v ratio, less likely to overheat. In prickly pear, microphylly is extreme where there aren"t any leaves. Reduced leaf size to none at all in very hot/dry habitats.
