羊草(Leymus chinensis)叶片光合参数对干旱与复水的响应机理与模拟

Modeling the responses of leaf photosynthetic parameters of Leymus chinensis to drought and rewatering

利用典型草原优势植物羊草（Leymus chinensis）对不同水分胁迫与复水响应的植物光合生理生态模拟实验与野外观测资料，分析研究了羊草叶片光合参数Kcmax（Rubisco的最大羧化速率）、Jmax（最大光合电子传递速率）和TPU（磷酸丙糖利用率）对干旱与复水的响应机理。结果表明，无论是模拟实验还是野外观测均显示羊草叶片的光合参数随着土壤水分的增加呈抛物线曲线变化，但各光合参数最大值对土壤水分的响应不同。温室模拟下的羊草光合参数Vcmax，Jmax和TPU在土壤含水量分别在15．56％，15．89％和16．23％时达到最大，而野外观测羊草的光合参数Vcmax，Jmax和TPU在土壤含水量分别为16．89％，17％和16．79％时达到最大。复水后羊草植株叶片光合参数的变化取决于前期干旱的影响，土壤含水量18％～19％和15％～16％处理的羊草复水后光合参数能够恢复正常，前者甚至超过正常水平，说明适宜的水分胁迫在复水后能够提高羊草叶片的光合能力，促进光合作用；土壤含水量10％～12％和7％～9％处理下的羊草复水后光合参数则不能恢复到正常水平。土壤含水量15％～16％可能是羊草光合能力在水分胁迫后能否恢复的阈值。

The global environmental change caused by the greenhouse gas emissions led to the increasing changes of temperature and precipitation patterns, and drought and other extreme weather events have occurred frequently. In order to understand and predict the effects of global change on terrestrial ecosystems, it is necessary to obtain the responses of leaf photosynthetic parameters to global change required by process-based model. The responses of photosynthetic parameters of Leymus chinensis to drought and rewatering would be studied in this paper, in order to reveal the mechanisms of the photosynthetic parameters of Leymus ehinensis responding to water stress and rewatering, and to develop the model of photosynthesis parameters responding to water and temperature for accurately simulating photosynthesis. The photosynthetic parameters of typical steppe grass Leymus chinensis was studied based on the data from the greenhouse simulating experiment in Institute of Botany, the Chinese Academy of Sciences and the field observation in Inner Mongolia typical steppe ecosystem research station, Institute of Atmospheric Environment, China Meteorological Administration, Shenyang. The photosynthetic parameters V cmax （ the maximum rate of carboxylation）, Jmax （ the maximum potential rate of electron transport） and TPU （the triose phosphate utilization） were obtained from the ACI curve （the relationship curve of net photosynthetic rate and intercellular CO2 concentration） of Leymus chinensis measured by the portable photosynthesis system （ Li-cor, Lincoln, NE, USA）. The relationship between the photosynthetic parameters of Leymus chinensis and soil moisture content could be expressed as a parabola curve. The maximum values of V J and TPU would appear when the soil moisture contents were 15.56% , 15.89% and 16.23% in greenhouse conditions and 16.89%, 17% and 16.79% in the field, respectively. The influence of rewatering on the photosynthetic parameters of Leymus ehinensis depended on the level of water stress prior to it. The photosynthetic parameters of Leymus chinensis under the soil moistures of 18%- 19% and 15% - 16% could recover from the water stress quickly, even some of them would increase. It implied that slight water stress could improve photosynthesis and photosynthetic parameters. However, the photosynthetic parameters under the soil moistures of 10%- 12% and 7%- 9% could not recover from the water stress previous. This study also indicated that when the soil moisture is less than 10% - 12%, the photosynthetic parameters of Leymus chinensis would not recover to the normal level even if the rewatering happens.