苹果叶片蒸腾速率动态模拟

The Dynamic Simulation of Transpiration in Apple Leaves

为了解不同小气候条件下苹果叶片的蒸腾速率(Tr)动态变化,构建了气孔-蒸腾耦合模型,并进行模拟研究。其中,叶片Tr根据Penman-Monteith公式计算,气孔导度(Gs)根据气孔的半机理模型计算。利用在‘富士’苹果园(Malus domestica Borkh.cv.‘Fuji’)观测数据拟合了相关模型参数。模拟结果表明,Tr随空气温度和叶片水势(Ψl)的增加而迅速增加,随CO2浓度的增加而降低。当光合有效辐射(PAR)低于光合作用的光饱和点时,Tr随PAR的增加而线性增加,超过光饱和点后Tr的增加不显著。结果显示,蒸腾作用主要是由饱和水气压差和Gs驱动,气孔变化是影响蒸腾的主要因素。不同小气候因子对Tr的影响各不相同,且它们之间还存在强烈的交互作用。在一天当中,Tr随Gs的增加(降低)而增加(降低)。在晴天,一天中单位面积的苹果上层叶片能蒸发2.7L水,其最大Tr约4mmol/(m2·s)。研究表明,通过构建叶片Tr和Gs耦合模型可模拟出不同小气候条件和Ψl下苹果叶片Tr的动态响应。

A coupled model of leaves transpiration rate（Tr） and stomatal conductance（Gs） was developed to simulate the dynamic variation of Tr in apple canopy.The model used the Penman-Monteith equation to compute the interactive effects between Tr and microclimatic factors.And Gs was caculated by the semi-mechanism model.The experiment was conducted in a ＇Fuji＇ apple（Malus domestica Borkh.cv＇.Fuji＇） orchard.The parameters of the model were tested by the data observed in upper canopy from 2007 to 2008 during the growing seasons.The mathematical simulation indicated that Tr increased rapidly with increasing Ta and Ψl;but decreased with increasing air CO2 concentration.Tr consistently increased with the increase of PAR when PAR was below photosynthesis light saturation point.And only a slightly increase was found when PAR excess light saturation point.It was shown that Tr was driven mainly by stomatal conductance,the most influential factor,and vapor pressure deficit.And the influences of these factors were different and there were strong interactive effects of various microclimatic factors on Tr.During the course of 1 day,transpiration increased（decreased） as net radiation and stomatal conductance increased（decreased）.Maximum transpiration rates of the upper canopy leaves were about 4 mmol/（m 2.s）on clear days.Over 24 h,a unit leaves area lost 2.7 L of water in clear weather and about 1.6 L in cloudy weather.In conclusion,the response of Tr to microclimatic factors and leaf water potential（Ψl）could be simulated by the coupled model.