Yun Kyungdahm, Timlin Dennis, Kim Soo-Hyung
School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA.
Adaptive Cropping Systems Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA.
Plants (Basel). 2020 Oct 14;9(10):1358. doi: 10.3390/plants9101358.
Plant simulation models are abstractions of plant physiological processes that are useful for investigating the responses of plants to changes in the environment. Because photosynthesis and transpiration are fundamental processes that drive plant growth and water relations, a leaf gas-exchange model that couples their interdependent relationship through stomatal control is a prerequisite for explanatory plant simulation models. Here, we present a coupled gas-exchange model for C4 leaves incorporating two widely used stomatal conductance submodels: Ball-Berry and Medlyn models. The output variables of the model includes steady-state values of CO2 assimilation rate, transpiration rate, stomatal conductance, leaf temperature, internal CO2 concentrations, and other leaf gas-exchange attributes in response to light, temperature, CO2, humidity, leaf nitrogen, and leaf water status. We test the model behavior and sensitivity, and discuss its applications and limitations. The model was implemented in Julia programming language using a novel modeling framework. Our testing and analyses indicate that the model behavior is reasonably sensitive and reliable in a wide range of environmental conditions. The behavior of the two model variants differing in stomatal conductance submodels deviated substantially from each other in low humidity conditions. The model was capable of replicating the behavior of transgenic C4 leaves under moderate temperatures as found in the literature. The coupled model, however, underestimated stomatal conductance in very high temperatures. This is likely an inherent limitation of the coupling approaches using Ball-Berry type models in which photosynthesis and stomatal conductance are recursively linked as an input of the other.
植物模拟模型是对植物生理过程的抽象，有助于研究植物对环境变化的响应。由于光合作用和蒸腾作用是驱动植物生长和水分关系的基本过程，一个通过气孔控制来耦合它们相互依存关系的叶片气体交换模型是解释性植物模拟模型的先决条件。在此，我们提出了一个适用于C4叶片的耦合气体交换模型，该模型纳入了两个广泛使用的气孔导度子模型：鲍尔-贝里模型和梅德林模型。该模型的输出变量包括二氧化碳同化率、蒸腾速率、气孔导度、叶片温度、内部二氧化碳浓度以及其他叶片气体交换属性的稳态值，这些值是对光照、温度、二氧化碳、湿度、叶片氮含量和叶片水分状况的响应。我们测试了模型的行为和敏感性，并讨论了其应用和局限性。该模型是使用一种新颖的建模框架在Julia编程语言中实现的。我们的测试和分析表明，在广泛的环境条件下，模型行为具有合理的敏感性和可靠性。在低湿度条件下，两个在气孔导度子模型上不同的模型变体的行为彼此有很大偏差。该模型能够复制文献中发现的转基因C4叶片在中等温度下的行为。然而，耦合模型在非常高的温度下低估了气孔导度。这可能是使用鲍尔-贝里类型模型的耦合方法的一个固有局限性，在这种方法中，光合作用和气孔导度作为对方的输入被递归地联系起来。
