[Effects of different NO-N/NH-N ratios on cucumber seedlings growth, nitrogen absorption and metabolism under suboptimal temperature and light intensity].

Cucumber (cv. Zhongnong 26) was used as material, the effects of NO-N/NH-N ratios on growth and physiological characteristics of cucumber seedlings under suboptimal temperature and light intensity (18 ℃/10 ℃,180 ± 20 μmol·m·s) were studied. Total nitrogen in the nutrient solution was equal and three NO-N/NH-N ratios, 26:2, 21:7 and 14:14, were applied as treatments. The results showed that cucumber treated by NO-N/NH-N=21:7 had the longest total root length, the biggest root volume and root surface area, and the maximum number of root tips. H-ATPase activity and relative expression of genes encoding nitrate transporter (NRT) and ammonium transporter (AMT) in cucumber roots were increased significantly by the treatment of NO-N/NH-N=21:7. In addition, nitrate reductase (NR), glutamine synthetase (GS) and glutamate synthase (GOGAT) in cucumber leaves under the treatment of NO-N/NH-N=21:7 were higher. As a result, the nitrogen content and biomass of cucumber were significantly increased. Compared with the plants under the treatment of NO-N/NH-N=26:2 or 14:14, cucumber seedlings under the treatment of NO-N/NH-N=21:7 had the highest biomass and total dry mass (DM) which were increased by 14.0% and 19.3% respectively under suboptimal temperature and light intensity. In conclusion, under suboptimal environmental conditions, NO -N/NH-N ratio could be adjusted to increase nitrogen absorption and metabolism of cucumber and alleviate the de-trimental effects caused by suboptimal conditions and promoted the cucumber growth.