Ball-Berry气孔导度模型及其修正模型是评价植物叶片气孔调节的重要工具。该文从CO₂分子在叶片气孔中扩散这个最基本的物理过程出发, 应用物理学中的分子扩散和碰撞理论、流体力学与植物生理学等知识, 严格推导出叶片气孔导度的机理模型。利用美国Li-Cor公司生产的Li-6400光合作用测定仪控制CO₂浓度、湿度和温度, 测量了华北平原冬小麦(Triticum aestivum)的光响应数据和气孔导度数据。拟合结果表明: 推导的气孔导度机理模型较之Ball-Berry气孔导度模型和Tuzet等气孔导度模型, 能更好地描述冬小麦的气孔导度与净光合速率之间的关系。如果用气孔导度的机理模型耦合光合作用对光响应的修正模型, 则耦合模型可以很好地描述华北平原冬小麦叶片气孔导度对光强的响应曲线, 并可直接估算冬小麦的最大气孔导度和对应的饱和光强, 同时可以研究最大气孔导度是否与最大净光合速率同步的问题。拟合结果还表明: 冬小麦在30 ℃、560 μmol·mol^-1CO₂, 或在32 ℃、370 μmol·mol^-1CO₂条件下, 最大气孔导度与最大净光合速率并不同步。

Aims The stomatal conductance model of Ball-Berry and its subsequent refinements is an important tool to evaluate performance of stomatal regulation of plant leaves. Our objective was to derive the mechanism model of stomatal conductance and provide a theoretical basis for these empirical models of stomatal conductance.
Methods By means of the diffusion and collision theory of CO₂ gas in physics, hydromechanics and plant physiology, we derived a relationship between stomatal conductance of leaves, net photosynthetic rate and intercellular CO₂ concentration. We measured the light-response of photosynthetic rate and stomatal conductance of Triticum aestivum under different chamber CO₂ concentrations and different air temperatures in North China Plain using a gas analyzer Li-6400. The measured data of stomatal conductance of T. aestivum to irradiance in North China Plain were simulated by coupling the mechanism model of stomatal conductance and non-rectangular hyperbola model, rectangular hyperbola model and modified model of light-response of photosynjournal.
Important findings A mechanism model of stomatal conductance was derived without additional hypotheses. It determined that the Ball-Berry stomatal conductance model had sound theoretical basis despite the model having deficiencies. The mechanism model shows advantages over the Ball-Berry model and model of Tuzet et al. for T. aestivum. If the mechanism model of stomatal conductance is coupled with a modified model of light-response of photosynjournal, the coupled model could simulate well the light-response data of stomatal conductance of T. aestivum. The fitted results show that stomatal conductance of T. aestivum to irradiance increases with light intensity until saturation light intensity, and then decreases with light intensity. The saturation light intensity and maximum stomatal conductance of T. aestivum can be calculated directly by the coupled model. Furthermore, we can use the coupled model to study whether maximum stomatal conductance coincides with maximum net photosynthetic rate. The fitted results also show that the maximum stomatal conductance and the maximum net photosynthetic rate are not synchronous at 30 ℃ and 560 μmol·mol^-1 CO₂ or 32 ℃ and 370 μmol·mol^-1CO₂. Additionally, the coupled model can describe not only part of the light-response curve of stomatal conductance below light saturation, but also the range of levels above the saturation light intensity under different environmental conditions.