Farquhar Graham D, Busch Florian A
Research School of Biology, Australian National University, Acton, ACT, 2601, Australia.
New Phytol. 2017 Apr;214(2):570-584. doi: 10.1111/nph.14512.
Mitochondrial respiration often appears to be inhibited in the light when compared with measurements in the dark. This inhibition is inferred from the response of the net CO assimilation rate (A) to absorbed irradiance (I), changing slope around the light compensation point (I ). We suggest a model that provides a plausible mechanistic explanation of this 'Kok effect'. The model uses the mathematical description of photosynthesis developed by Farquhar, von Caemmerer and Berry; it involves no inhibition of respiration rate in the light. We also describe a fitting technique for quantifying the Kok effect at low I. Changes in the chloroplastic CO partial pressure (C ) can explain curvature of A vs I, its diminution in C plants and at low oxygen concentrations or high carbon dioxide concentrations in C plants, and effects of dark respiration rate and of temperature. It also explains the apparent inhibition of respiration in the light as inferred by the Laisk approach. While there are probably other sources of curvature in A vs I, variation in C can largely explain the curvature at low irradiance, and suggests that interpretation of day respiration compared with dark respiration of leaves on the basis of the Kok effect needs reassessment.
与黑暗中的测量结果相比，线粒体呼吸在光照下似乎常常受到抑制。这种抑制是根据净二氧化碳同化率（A）对吸收辐照度（I）的响应推断出来的，在光补偿点（I ）附近斜率发生变化。我们提出了一个模型，该模型对这种“科克效应”提供了一个合理的机理解释。该模型使用了由法夸尔、冯·卡默勒和贝里提出的光合作用数学描述；它并不涉及光照下呼吸速率的抑制。我们还描述了一种用于在低I值下量化科克效应的拟合技术。叶绿体二氧化碳分压（C ）的变化可以解释A与I关系曲线的曲率、C4植物中该曲线的变缓和C3植物在低氧浓度或高二氧化碳浓度下该曲线的变缓，以及暗呼吸速率和温度的影响。它还解释了莱伊斯克方法所推断的光照下呼吸的明显抑制。虽然A与I关系曲线的曲率可能还有其他来源，但C 的变化在很大程度上可以解释低辐照度下的曲率，并表明基于科克效应来解释叶片的日间呼吸与暗呼吸相比需要重新评估。
