Department of Biology, Sonoma State University, Rohnert Park, CA, USA.
Plant Cell Environ. 2011 Jan;34(1):89-112. doi: 10.1111/j.1365-3040.2010.02228.x. Epub 2010 Oct 7.
Leaf respiration continues in the light but at a reduced rate. This inhibition is highly variable, and the mechanisms are poorly known, partly due to the lack of a formal model that can generate testable hypotheses. We derived an analytical model for non-photorespiratory CO₂ release by solving steady-state supply/demand equations for ATP, NADH and NADPH, coupled to a widely used photosynthesis model. We used this model to evaluate causes for suppression of respiration by light. The model agrees with many observations, including highly variable suppression at saturating light, greater suppression in mature leaves, reduced assimilatory quotient (ratio of net CO₂ and O₂ exchange) concurrent with nitrate reduction and a Kok effect (discrete change in quantum yield at low light). The model predicts engagement of non-phosphorylating pathways at moderate to high light, or concurrent with processes that yield ATP and NADH, such as fatty acid or terpenoid synthesis. Suppression of respiration is governed largely by photosynthetic adenylate balance, although photorespiratory NADH may contribute at sub-saturating light. Key questions include the precise diel variation of anabolism and the ATP : 2e⁻ ratio for photophosphorylation. Our model can focus experimental research and is a step towards a fully process-based model of CO₂ exchange.
叶片呼吸在光照下仍会继续，但呼吸速率会降低。这种抑制作用具有很强的可变性，其机制也知之甚少，部分原因是缺乏一个可以生成可检验假说的正式模型。我们通过求解与广泛使用的光合作用模型相耦合的 ATP、NADH 和 NADPH 的稳态供应/需求方程，为非光呼吸 CO₂释放推导了一个分析模型。我们使用该模型评估了光对呼吸抑制的原因。该模型与许多观察结果一致，包括在饱和光下具有高度可变的抑制作用、在成熟叶片中具有更大的抑制作用、与硝酸盐还原同时发生的同化率（净 CO₂和 O₂交换的比率）降低，以及 Kok 效应（在低光下量子产率的离散变化）。该模型预测在中等至高光下或与产生 ATP 和 NADH 的过程（如脂肪酸或萜烯合成）同时，会启用非磷酸化途径。呼吸抑制主要受光合作用腺嘌呤核苷酸平衡控制，尽管光呼吸 NADH 可能在亚饱和光下发挥作用。关键问题包括同化作用的精确昼夜变化和光磷酸化的 ATP : 2e⁻ 比值。我们的模型可以集中进行实验研究，是朝着基于全过程的 CO₂交换模型迈出的一步。
