Department of Biology, University of Kaiserslautern, Postfach 3049, D-6750, Kaiserslautern, Federal Republic of Germany.
Planta. 1979 Jan;145(3):219-23. doi: 10.1007/BF00454444.
Using an open gas-exchange system, apparent photosynthesis, true photosynthesis (TPS), photorespiration (PR) and dark respiration of sunflower (Helianthus annuus L.) leaves were determined at three temperatures and between 50 and 400 μl/l external CO2. The ratio of PR/TPS and the solubility ratio of O2/CO2 in the intercellular spaces both decreased with increasing CO2. The rate of PR was not affected by the CO2 concentration in the leaves and was independent of the solubility ratio of oxygen and CO2 in the leaf cell. At photosynthesis-limiting concentrations of CO2, the ratio of PR/TPS significantly increased from 18 to 30°C and the rate of PR increased from 4.3 mg CO2 dm(-2) h(-1) at 18°C to 8.6 mg CO2 dm(-2) h(-1) at 30°C. The specific activity of photorespired CO2 was CO2-dependent but temperature-independent, and the carbon traversing the glycolate pathway appeared to be derived both from recently fixed assimilate and from older reserve materials. It is concluded that PR as a percentage of TPS is affected by the concentrations of O2 and CO2 around the photosynthesizing cells, but the rate of PR may also be controlled by other factors.
利用开放气体交换系统，在三个温度下和 50 到 400 μl/l 的外部 CO2 之间，测定了向日葵（Helianthus annuus L.）叶片的表观光合作用、真光合作用（TPS）、光呼吸（PR）和暗呼吸。随着 CO2 的增加，PR/TPS 的比值和细胞间隙中 O2/CO2 的溶解度比值均降低。PR 的速率不受叶片中 CO2 浓度的影响，也不受叶片细胞中氧气和 CO2 溶解度比值的影响。在 CO2 浓度限制光合作用的情况下，PR/TPS 的比值从 18 到 30°C 显著增加，PR 的速率从 18°C 时的 4.3 mg CO2 dm(-2) h(-1)增加到 30°C 时的 8.6 mg CO2 dm(-2) h(-1)。光呼吸 CO2 的比活度是 CO2 依赖性的，但与温度无关，穿过乙醛酸途径的碳似乎既来自最近固定的同化产物，也来自较老的储备物质。因此得出结论，PR 作为 TPS 的百分比受光合作用细胞周围 O2 和 CO2 浓度的影响，但 PR 的速率也可能受到其他因素的控制。
