Effect of Different Light Intensity and CO_2 Concentration on Photosynthesis and Chlorophyll Fluorescence Parameters of Grafting Cucumber Leaves in Greenhouse

With grafted cucumber in greenhouse as test material,the diurnal changes photosynthetic rate and chlorophyll fluorescence parameters of grafting cucumber leaves in greenhouse were studied under different light intensity and CO2 concentration,and the relationship between photosynthetic rate and chlorophyll fluorescence parameters was also analyzed to provide theoretical basis and practical support for high yield and good quality cultivation of grafting cucumber in greenhouse.The results showed that the diurnal changes of Pn,qP under 100%light intensity were double-peak curve,and a phenomenon of midday depression appeared.It under 15% and 32%light intensity were unimodal curve,showed that proper shade could effectively relieve the midday depression phenomenon.The Pn values of treatment combination of100%light intensity+high concentration of CO2 was the biggest,it could effectively improve photosynthetic efficiency,so it was the better combination.The Fv/Fm,qP,NPQ values under 32%light intensity were the biggest increasing middle concentration of CO2 and photosynthetic rate(Pn)value was bigger also,so it was a better combination,showed that under the condition of weak light in winter,increasing CO2 concentration appropriately could improve photosynthetic efficiency,then reduced the influence of light intensity inadequate.