桑树叶片光合生理性状对土壤水分含量和光照强度的响应

用CIRAS-2便携式光合仪测定不同土壤水分含量条件下2年生桑树叶片净光合速率(Pn)、蒸腾速率(Tr)、水分利用效率(WUE)、光能利用效率(LUE)等光合生理参数,分析桑叶光合生理特性对土壤水分含量和光照强度的响应规律,为建立桑树的节水高产栽培技术提供理论依据。结果表明:随着土壤相对含水量(RWC)的降低(由94.3%梯度降至28.7%),桑叶的Pn、表观量子效率(Φ)、LUE先升高后降低,暗呼吸速率(Rd)、光补偿点(LCP)先降低后升高,Tr、光饱和点(LSP)一直呈降低趋势。综上认为,桑树叶片的光合生理参数对光照强度、土壤水分含量的变化具有明显的阈值响应,有利于桑树进行高光合作用和维持高水分利用效率的适宜土壤相对含水量为44.8%～77.8%,最适土壤相对含水量为52.0%左右,适宜的光照强度为800～2 000μmol/(m2·s)。

Responses of Photosynthetic Physiological Characteristics of Mulberry Leaf to Soil Moisture and Light Intensity

In present study,we measured net photosynthetic rate(Pn),transpiration rate(Tr),water use efficiency(WUE) and light use efficiency(LUE) of two-year-old mulberry leaves under different soil water conditions by using CIRAS-2 portable photosynthesis system.The response pattern of photosynthetic physiological parameters of mulberry leaf to soil moisture and light intensity was analyzed to provide theoretical basis for developing mulberry cultivation technology with characteristics of water saving and high yield.The results showed that with the decreasing of relative soil water content(from 94.3% to 28.7%),Pn,apparent quantum yield(Φ) and LUE increased first and then declined,while dark respiration rate(Rd) and light compensation point(LCP) decreased first and then increased,and Tr and light saturation point(LSP) decreased all the time.The above results suggest that photosynthetic physiological parameters of mulberry leaves had threshold response to the change of soil moisture and light intensity.Higher net photosynthetic rate and water use efficiency were observed under the conditions of relative soil water contents from 44.8% to 77.8%(the optimum relative soil water contents were around 52.0%) and photosynthetic active radiation from 800 to 2 000 μmol/(m2·s).