PLANT PHYSIOLOGY
PHOTOSYNTHESIS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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) have higher rates of photorespiration.
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cancontinue to fix CO2 even at relatively low CO2 concentrations and high oxygen concentrations.
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do not use rubisco for carbon fixation.
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grow better under cool, moist conditions.
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Detailed explanation-1: -C4 plants can absorb CO2 even at much lower concentration i.e. 1-2 parts per million while C3 plants can absorb it only when it is about 50 parts per million. C4 plants can do photosynthesis in excessive heat and intense light where C3 plants are unable to do so.
Detailed explanation-2: -C4 plants such as maize, sorghum, and sugarcane, approximately have 50% higher photosynthesis efficiency than those of C3 plants such as rice, wheat, and potato [1]. This is because the different mechanism of carbon fixation by the two types of photosynthesis, as illustrated in Figure
Detailed explanation-3: -In C3 plants, the carbon dioxide fixation takes place only at one place. In C4 plants, the carbon dioxide fixation takes places twice (one in mesophyll cells, second in bundle sheath cells). C3 plants possess only one CO2 acceptor. C4 plants possess two CO2 acceptors (primary acceptor and secondary acceptor).
Detailed explanation-4: -The response of C3 species to increased [CO2] may be more positive than that of C4 species because photosynthetic rate of C3 species increases by approximately 58% due to doubled [CO2] (Drake et al. 1997). However, in C4 species, the photosynthesis is nearly saturated under recent ambient [CO2] (von Caemmerer et al.
Detailed explanation-5: -RuBisCO takes up oxygen to perform photorespiration when carbon dioxide concentration is low. In C4 plants, since carbon dioxide concentration is high at the RuBisCO site thus, photorespiration is highly reduced. C4 plants possess special leaf anatomy called ‘Kranz anatomy’ and undergo the C4 pathway of photosynthesis.