Effects Of CO₂ Concentration On Growth And Photosynthetic Physiology Of Cucumber In Greenhouse

In order to select the optimum CO2 fertilization concentration,we used the local cucumber cultivar"Xinghai 7" as the material to isolate four equal and independent spaces by using plastic films in a solar greenhouse.Then,the cucumbers were processed with different CO2 concentrations for observing the effects of cucumbers growth,photosynthetic physiology and chlorophyll fluorescence of photosystem II at different stages of cucumber growth in the greenhouse.The experimental results were as follows:1.Compared with CK,the 1200 ?mol/mol of CO2-treated group's plant height increased by 43.9%,stem diameter increased by 31.0%,leaf area increased by 25.3%,the number of leaves increased by 3,single cucumber fruit weight increased by 16.65%,yield of per plant increased by 1.34 times,yield of small plot increased by 39.0%.In addition,compared with CK group,fruit length increased by 29.41%and fruit diameter increased by 22.43%when the growth of the melon for 11st days.The treatment of 1200?mol/mol of CO2 was better than other treatments.2.At seedling stage,compared with CK,the 1600 ?mol/mol of CO2-treated group's leaf chlorophyll content increased by 12.7%,net photosynthetic rate increased by 115.0%,stomatal conductance and transpiration rate decreased by 45.6%and 20.3%respectively.apparent quantum efficiency increased by 38.6%,light saturation point decreased by 36.4%,light saturation point increased by 102.5%,the effective PS ? quantum yield increased by 145.4%,coefficient of photochemical quenching increased by 142.5%,and the non-photochemical quenching decreased by 16.7%.The treatment of 1600 ?mol/mol of C02 was better than other treatments at the seedling stage.3.At initial flowering stage,compared with CK,the 1200 ?mol/mol of CO2-treated group's leaf chlorophyll content increased by 16.0%,net photosynthetic rate increased by 59.3%,stomatal conductance and transpiration rate decreased by 36.4%and 23.6%,respectively,light saturation point decreased by 50.0%,light saturation point increased by 30.4%,maximum quantum efficiency of photosystem ? photochemistry increased by 17.9%,effective PS ? quantum yield increased by 26.5%,coefficient of photochemical quenching increased by 26.4%,and non-photochemical quenching decreased by 27.8%.The treatment of 1200 ?mol/mol of CO2 was better than other treatments at initial flowering stage.4.At full fruit stage,compared with CK,the 1200 ?mol/mol of CO2-treated group's leaf chlorophyll content increased by 16.27%,net photosynthetic rate increased by 61.0%,stomatal conductance and transpiration rate decreased by 5.8%and 14.7%respectively,apparent quantum efficiency increased by 23.0%,light compensation point decreased by 10.07%,light saturation point increased by 39.87%,effective PS ? quantum yield increased by 12.9%,coefficient of photochemical quenching increased by 8.5%and non-photochemical quenching decreased by 35.5%.The treatment of 1200 ?mol/mol of CO2 was better than other treatments at full fruit stage.Therefore,CO2 fertilization can effectively improve the biomass and photosynthetic capacity of cucumber plants in greenhouse.In this study,We found that the demands for CO2 in diverse growth and development stages were different.Furthermore,we discovered that the optimum CO2 concentration at seedling stage was 1600 ?mol/mol,at initial flowering stage was 1200 ?mol/mol and at full fruit stage was 1200 ?mol/mol.