黄荆光合作用对土壤逐渐干旱和CO 2浓度的响应

Response of photosynthesis of Vitex negundo to soil gradual drought and CO 2 concentration.

应用CIRAS-2型光合测定系统,测定土壤逐渐干旱过程中2年生盆栽黄荆(Vitex negundo)光合作用的CO 2响应过程,采用直角双曲线修正模型和指数改进模型对其响应过程进行拟合,分析了黄荆光合作用与土壤水分的定量关系。结果表明:2种模型都能较好地拟合黄荆光合作用CO 2响应过程,当土壤相对含水量(RWC)在54.6%~78.1%时,指数改进模型的整体拟合效果更好,超出此范围时直角双曲线修正模型具有更好的拟合效果。当RWC分别在35.4%~90.4%、35.4%~90.4%、44.2%~68.1%和54.6%~68.1%时,指数改进模型拟合对应水分区间的羧化效率(CE)、光合能力(P nmax)、CO 2补偿点(Γ)和光呼吸速率(R p)更为精准,超出各水分范围时直角双曲线修正模型拟合精度更高。在各个土壤水分下对CO 2饱和点(CSP)的拟合精度均表现为直角双曲线修正模型高于指数改进模型。通过建立平均净光合速率(n)与土壤相对含水量(RWC)的函数关系,明确了维持黄荆光合作用较高水平的RWC范围为49.5%~81.2%,最适宜的RWC在65.4%左右,维持黄荆光合作用最低RWC在19.9%左右。

Using CIRAS-2 photosynthetic system,the CO 2 response of Vitex negundo photosynthesis was measured in the process of soil drying gradually.The CO 2 response process of V.negundo were fitted by modified rectangular hyperbola model and modified exponential model and the quantitative relationship between photosynthesis and soil moisture was analyzed.The results showed that the CO 2 response process of V.negundo photosynthesis could be well fitted by the two models,and when the relative soil water content(RWC)was between 54.6%and 78.1%,the overall fitting effect of the modified exponential model was better.When the RWC was beyond the range,the modified rectangular hyperbola model had better fitting effect.When RWC was 35.4%~90.4%,35.4%~90.4%,44.2%~68.1%,54.6%~68.1%,respectively,it was more accurate to fit the carboxylation efficiency(CE),photosynthetic capacity(P nmax),CO 2 compensation point(Γ)and photorespiration rate(R P)of the corresponding water range with the modified exponential model,the fitting accuracy of the modified rectangular hyperbola model was higher when the RWC was beyond the range.The fitting accuracy of CO 2 saturation point(CSP)under different soil moisture was higher with the modified rectangular hyperbola model than with the modified exponential model.By establishing the function relationship between the average net photosynthetic rate(n)and the relative soil water content(RWC),it was concluded that the RWC range of maintaining the higher level of photosynthesis of V.negundo was between 49.5%and 81.2%,the most suitable RWC was about 65.4%,and the lowest RWC of maintaining photosynthesis of V.negundo was about 19.9%.