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六十年代关于光合作用 C_3、C_4途径的研究证明,植物在光下进行光合作用吸收 CO_2放出O_2的同时,还进行一种相反过程,即吸收 O_2放出 CO_2的“光呼吸”现象。光呼吸所分解的原料是光合作用的中间产物——乙醇酸。它不象正常呼吸那样,可提供植物生命活动的“能量”。目前认为是一种无谓的消耗。C_4植物如玉米、高粱、甘蔗等,在光合作用过程中,由于具有特殊的 CO_2固定途径,其光呼吸所释放的 CO_2能很快地被光合作用重新吸收利用。因此,光呼吸很微弱,CO_2补偿点低,甚至接近于零,光合效率高;而 C_3植物如水稻、小麦、大豆、烟草等,则具有较强的光呼吸,其 CO_2补偿点高,约为60P·P·M 或更高,光合效率低。C_3植物通过光呼吸损失的 CO_2常达光合作用同化 CO_2的30～50%,这对植物有机物的积
Studies on the pathways of C_3 and C_4 in photosynthesis in the 1960s proved that plants under light photosynthesis absorbed CO_2 to emit O_2, and an opposite process was also carried out to absorb the phenomenon of CO_2 “photorespiration” absorbed by O_2. Photo Respiratory decomposition of raw materials is the intermediate product of photosynthesis - glycolic acid. It does not provide the “energy” of plant life activities, as normal breathing does. Currently considered a senseless consumption. C_4 plants such as corn, sorghum, sugar cane and so on, in the process of photosynthesis, due to the special CO_2 fixed pathway, the CO_2 released by its photorespiration can quickly be reabsorbed by photosynthesis. Therefore, the photorespiration is very weak, CO 2 compensation point is low, even close to zero, photosynthetic efficiency; and C 3 plants such as rice, wheat, soybeans, tobacco, etc., has strong photorespiration, the CO 2 compensation point is high, 60P · P · M or higher, photosynthetic efficiency is low. C_3 photosynthesis through photosynthetic CO2 loss of photosynthesis often assimilates CO_2 30 ~ 50%, which plant organic matter plot