Abstract: In order to investigate the effect of water use efficiency (WUE) on the interaction between water cycle and carbon in ecosystem, we developed a light-response model of intrinsic water use efficiency (WUE_i) and a light-response model of instantaneous water use efficiency (WUE_inst) based on a mechanistic model of light-response of photosynthesis, respectively. Meanwhile, both WUE_i and WUE_inst of soybean (Glycine max) were simulated by the corresponding model. The results showed that WUE_inst increased with CO₂ concentration, while WUE_i did not have such obvious change tendency. Furthermore, the maximum WUE_i and WUE_inst at 600 μmol·mol^-1 were 2.82 and 1.94 times higher than that at 300 μmol·mol^-1, respectively. If WUE_i and WUEinst were converted into the same unit (e.g. μmol CO₂·mol^-1 H₂O or μmol CO₂·mmol^-1 H₂O), the latter was 39 times or more than the former. Consequently, it is concluded that WUE_inst could more truly reflect the WUE of soybean leaves. Moreover, this study provides a mathematical tool for quantitative investigation of the variation of WUE of plant leaves.

Key words: intrinsic water use efficiency, instantaneous water use efficiency, mechanistic model of photosynthesis-response, water use efficiency model

摘要： 为探究水分利用效率(WUE)对生态系统水循环和碳循环相互作用的影响,本研究利用光合作用对光响应的机理模型构建内禀水分利用效率模型和瞬时水分利用效率模型,并利用2个模型拟合大豆叶片的内禀水分利用效率(WUE_i)和瞬时水分利用效率(WUE_inst)。结果表明,瞬时水分利用效率随着CO₂浓度的增加而增大;内禀水分利用效率则不存在明显的变化规律。CO₂浓度为600 μmol·mol^-1时的最大瞬时水分利用效率和最大内禀水分利用效率分别是300 μmol·mol^-1CO₂下的2.82倍和1.94倍。将内禀水分利用效率和瞬时水分利用效率换算成相同的单位(如μmol CO₂·mol ^-1 H₂O或μmol CO₂·mmol^-1 H₂O),后者是前者的39倍,甚至更多。综上所述,利用瞬时水分利用效率能更真实地反映出大豆叶片的水分利用效率。本研究为定量研究植物叶片水分利用效率的变化规律提供了数学工具。

关键词: 内禀水分利用效率, 瞬时水分利用效率, 光响应机理模型, 水分利用效率模型