Studies On Effects Of Different Nitrogen And Light Intensity Levels On Vegetable Biomass Under Water Stress Control

The objective of this study is to evaluate the effect of different light intensities and nitrogen supply levels with different water stress on the biomass of Brassica Chinensis L. (Hangzhou you dong er) by a hydroponic experiment. The results showed that the dry biomass of the cabbages at 0%[w/v]PEG,100% natural light intensity (H1 L3) was significantly higher than in weak light intensity and water stress treatments under the same nitrogen treatment. Decreased nitrate was achieved in low nitrogen supply and high light intensity level. An almost 1.7-fold increase in nitrate content was found in plants at the 100% nitrogen supply and 0%PEG level (N4H1), compared with weak light intensity(L1).Under high light intensity, the plant has a high content of soluble sugar and increased nitrogen assimilation capacity. For plants grown on full nitrogen supply level and 0%PEG (N4H1) condition, Nitrate reductase, Glutamate dehydrogenase, Glutamine synthetase activity showed 65%,44% and 35% lower in weak light intensity(L2) condition than in high light intensity condition(L3). An optimal yield was reached at 60% of the traditional nitrogen application in the presence of adequate high light intensity supply and normal water content.We also evaluate the effect of different light intensities and nitrogen supply levels with different soil on the yield of Cucumissativus L. (Bomei 11) and Lycopersicon esculentum Mill (Zhongwang 9). The results show that high light intensity was especially important to the growth of the fruits. Under high light intensity, the plants had a high content of soluble sugar,ascorbic acid and low content of nitrogen. An almost 1.3-fold and 1.6-fold increase in soluble sugars was found in cucumber and tomoto at the 350Kgha^-1 nitrogen supply level (N2) and high light intensity treatment (L3), weak light intensity (L1).While Nitrate reductase decreased by 71% and 90% respectively in weak light intensity (L1) compared with high light intensity treatment (L3). An optimal yield was reached at 60% of the traditional nitrogen application (350 Kgha^-1) in the presence of adequate high light intensity supply and soil water content. Modulating the relationship between water stress, light intensity and nitrogen supply level could increase the biomass and promote the quality of the plant.