不同连作年限土壤对甜瓜幼苗叶绿素含量和光合特性的影响

目的]探讨不同连作年限的土壤对甜瓜幼苗叶绿素含量和光合特性的影响。方法]选取连作1、3、5和7年的土壤盆栽甜瓜，以露地非连作菜园土壤为对照。定植后30d，测定甜瓜幼苗叶绿素含量、光合及荧光动力学参数的变化情况。结果]随着连作年限的增加，甜瓜叶片叶绿素含量、净光合速率、气孔导度、蒸腾速率、PSⅡ最大光化学效率、PSⅡ实际光化学效率、光化学淬灭逐渐降低，但胞间CO2浓度和初始荧光升高。结论]连作易造成甜瓜叶绿素合成受阻，PSⅡ反应中心受到光化学损害，光合电子传递受抑制，表明甜瓜不耐连作，尤其不适宜长期连作。

Effects of the Continuous Cropping Soil on Chlorophyll Contents and Photosynthesis Characteristics of the Melon

Objective] The research aimed to explore the effects of the continuous cropping soil on chlorophyll contents and photosynthesis characteristics of the melon.Method] The continuous cropping soil of 0,1,3,5 and 7 years were used to plant melon,with noncontinuous open ground soil as CK.The chlorophyll contents,parameters of photosynthesis and chlorophyll fluorescence dynamics of the melon were investigated after planting 30 days.Result] The results showed that the chlorophyll contents,net photosynthetic rate,stomatal conductance,transpiration rate,maximum photochemical efficiency,actual photochemistry efficiency of PSII and photochemical quenching decreased gradually with increasing planting on the continuous cropping soil,whereas intercellular CO2 concentration and initial fluorescence increased.Conclusion] The result suggests that the synthesis of chlorophyll is restrained,and the center of PSⅡ reaction is injured led to inhibit electronic transferring under continuous cropping condition.At the same time,the result shows that the melon is unable to bear continuous cropping,especially in a long period.