The effect of exogenous sugar solution and high concentration of CO2 on the contents of sugar and protein of Betula platyphylla leaves

The content of total sugar,sucrose,fructose and protein in the leaves of 3-yr.-old Betula platyphylla was measured after the treatment by three exogenous sugar solutions(sucrose,fructose,glucose) and three high concentrations of CO2(700,1400,2100μL·L^-1) for about a month in 1998.The results showed that spraying three exogenous sugar solutions increased markedly the content of sugar and protein of leaves under 700μL·L^-1 and 1400μL·L^-1 CO2.The effect of spraying exogenous sucrose solution was the best among the three exogenous sugars.The treatment of spraying exogenous sugar solution and 2100μL·L^-1 CO2 constrained the accumulation of total sugar and protein of leaves.There was no difference in protein content of leaves when spraying glucose and fructose solutions under 700μL·L^-1 and 1400μL·L^-1 CO2.The treatrnent of 2100μL·L^-1 CO2 concentration significantly increased the contents of total sugar,sucrose,fructose,and protein of leaves compared with that of the 700μL·L^-1 and 1400μL·L^-1 CO2 except the plants spraying fructose solution.there was positive correlation between the content of sugar of leaves and CO2 concentration when spraying same exogenous sugar solution.