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Photorespiration, , e Itis athe light dependent process of oxygenation of RuBP and release of carbon, dioxide by photosynthetic organs of plants., , e Photorespiration decreases the rate of photosynthesis when oxygen concentration is, increased from 2-3% to 21%., , e Presence of light and higher concentration of Oxygen results in the binding of, RuBisCO enzyme with 02 to form., , RuBisCO + O2 — PGA + phosphoglycolate, , This pathway involves Chloroplast, Peroxisome and Mitochondria. Photorespiration do, , not occurs in C4 plants., , C3 plants C4 plants, , , , 1. The leaves show Kranz anatomy in, 1. The leaves do not have Kranz anatomy., oo leaves., 2. Photorespiration occurs., , 3. RuBisCO is the first acceptor of CO2., 4. PGA is the first stable product., , 2. Photorespiration does not occur., 3. PEP is the first acceptor of CO2., , 9/10, Material Downloaded From SUPERCOP, , 5. Plants are adapted to all climates. 4. OAA is the first stable product., 6. Mesophyll cells perform complete 5. Plants are adapted to tropical climate., , photosynthesis. 6. Mesophyll cells perform only initial, , fixation., , , , Factors affecting photosynthesis, , 1. Light- as light intensity increases, the rate of photosynthesis also increases until light, saturation point., , 2. Carbon dioxide concentration- with increase in concentration of CO, rate of, photosynthesis increase till the compensation point., , 3. Temperature- it does not influence the rate of photosynthesis directly but at higher, temperature enzyme activity is inhibited due to denaturation of enzymes which affect the, dark reaction., , 4. Water- due to increase in amount of water, rate of photosynthesis does not increase, , proportionally as after saturation no more water is required during photosynthesis., , Blackman’s Law of Limiting Factors states:, , If a chemical process is affected by more than one factor, then its rate will be determined by, the factor which is nearest to its minimal value: it is the factor which directly affects the, process if its quantity is changed.