The Effects Of Elevated CO₂with High Temperature Stress On The Metabolism Of Carbohydrate And Starch In Greenhouse-Cucumber

To investigate the regulation effect of elevated CO2to thermal damage on plants, taking the cucumber variety Jin You No.36as experimental material, research the effects of elevated CO2to the content of carbohydrate and starch, enzyme activities in sugar metabolism and some related physiological indexes. We study the relationship between the content of photosynthate in the leaves and fruits of the cucumber based on the theory of ’source and sink’, which is conductive to research the way to keep or increase the photosynthetic capacity of cucumber, and could offer scientific theoretical basis for the formulation of the production technology of cucumber produced in the greenhouse and under the high temperature in the summer. The results showed that:1Heat stress could decrease the leaf areas, reduce the content of chlorophyll, change the leaves yellow and white. At the same time, the growth of the plant under heat stress was restrained, the height of the plant was lower, but the stem diameter was higher. The leaf areas and the content of chlorophyll recovered significantly under the treatment of heat stress with CO2enrichment, the height and stem were also increased significantly.2CO2fertilization could break the phenomenon of "noon break" when the temperature was high at noon and boost the photosynthesis to continue. Heat stress could weaken the photosynthesis of the leaves and fasten the decomposition of starch,all of the content of carbohydrate*fructose-. sucrose and reducing sugar in the leaves increased, while the content of all kinds of the carbohydrate and starch decreased in the fruits. CO2fertilization under the treatment of heat stress could boost the photosynthesis of the plant, the content of fructose and sucrose in the leaves decreased, the content of carbohydrate%reducing sugar and starch increased, while he content of all kinds of the carbohydrate and starch increased in the fruits. CO2enrichment with heat stress could strengthen the sink strength and fasten the transportation of the photosynthetic products.3The correlation between the content of fructose and the activity of AI and NI were apparently higher in both leaves and fruits compared with the CK. The content of fructose was significantly and positively correlated with the activity of AI and NI in the leaves. The correlation between the content of sugar and the activity of SS in the leaves increased apparently with the CO2enrichment under the normal temperature, while the correlation between the content of sugar and the activity of SPS decreased. The correlation between the content of fructose and the activity of SPS increased which was significantly and positively correlated in the fruits. The correlation between the content of sucrose and the activity of SPS increased in the leaves under the treatment of CO2enrichment with heat stress, while the correlation between the content of sugar and the activity of SS decreased. Under the treatment of CO2enrichment with heat stress, the content of fructose was significantly and negatively correlated with the activity of SPS in the leaves, the content of sucrose was significantly and positively correlated with the activity of SS and was significantly and negatively correlated with the activity of AI and NI in the fruits, the content of fructose was significantly and positively correlated with the activity of SS.