What does optimization theory actually predict about crown profiles of photosynthetic capacity when models incorporate greater realism?
What does optimization theory actually predict about crown profiles of photosynthetic capacity when models incorporate greater realism?
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DOI：
10.1111/pce.12091
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发表时间：
2013-08-01
影响因子：
7.3
通讯作者：
Farquhar, Graham D.
中科院分区：
文献类型：
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作者：
Buckley, Thomas N.;Cescatti, Alessandro;Farquhar, Graham D.
植物冠部光合能力的测量曲线通常与平均辐照度的曲线不匹配：能力与辐照度的比率随着辐照度的增加而降低。这不同于从简单模型推断的最佳配置文件。为了确定这是否可以通过从这些模型中省略生理或物理细节来解释，我们使用一个新模型进行了一系列思维实验，该模型比以前的模型更加真实。我们使用光线跟踪来模拟水平均匀树冠中8000片树叶的辐照度。对于一个子样本的500片叶子，我们同时优化了氮分配（池之间代表羧化，电子传递和光捕获）和气孔导度使用transdermally明确的光合作用模型。几个模型功能造成的容量/辐照度比随辐照度系统地变化。然而，当叶片吸收率根据需要而变化，以优化光捕获N的分布时，容量/辐照度比通过树冠增加-也就是说，与所观察到的模式相反。这种趋势被抵消气孔或叶肉导度的限制，这导致叶绿体CO2浓度下降，随着光照的增加系统。我们的研究结果表明，高度相关的气孔导度的限制，可以帮助调和的假设，光合氮的最佳分配的意见。
Measured profiles of photosynthetic capacity in plant crowns typically do not match those of average irradiance: the ratio of capacity to irradiance decreases as irradiance increases. This differs from optimal profiles inferred from simple models. To determine whether this could be explained by omission of physiological or physical details from such models, we performed a series of thought experiments using a new model that included more realism than previous models. We used ray-tracing to simulate irradiance for 8000 leaves in a horizontally uniform canopy. For a subsample of 500 leaves, we simultaneously optimized both nitrogen allocation (among pools representing carboxylation, electron transport and light capture) and stomatal conductance using a transdermally explicit photosynthesis model. Few model features caused the capacity/irradiance ratio to vary systematically with irradiance. However, when leaf absorptance varied as needed to optimize distribution of light-capture N, the capacity/irradiance ratio increased up through the crown - that is, opposite to the observed pattern. This tendency was counteracted by constraints on stomatal or mesophyll conductance, which caused chloroplastic CO2 concentration to decline systematically with increasing irradiance. Our results suggest that height-related constraints on stomatal conductance can help to reconcile observations with the hypothesis that photosynthetic N is allocated optimally.