Effect of nitrogen on taste compounds,nitrate and yield of cucumber in solar-greenhouse

In order to examine the relationship between nitrogen rate,flaver quality,and yield of cucumber,an experiment was conducted to study the effect of nitrogen on taste compounds,nitrate concentration and enzyme activities of cucumber fruits in solar-greenhouse using single factor design.Results showed that the soluble sugar and Vc contents decreased with the increase of N application rate within the range of 0900 kg/ha,while organic acids,tannin and nitrate concentration increased gradually with increasing of N.There was a significant correlation between soluble sugar of cucumber fruits and SPS activities in leaves,Vc content and APX activities,and nitrate concentration and NR separately.The SPS,APX and NR activities of leaves were all higher than those of fruits.There were significant difference among different treatments on yield.The yield of N300 and N600 were higher than that of N0 remarkably,but N900 was lower than that of N0 obviously.600kg/ha N could be considered as the top limit under this experimental condition.