Effects Of Water And Nitrogen Fertilizer On Growth And Nitrogen Metabolism Of Maize Seedling

Water and nitrogen are key factors for the growth of plant. In order to research themechanism for the functions of water, nitrogen in the growth of plant, We studied theeffects of water(8.8%, 13.2%, 17.6%), nitrogen forms (NANO₃, NH₄Cl, NH₄NO₃. Urea)and amount (0.1gN/kg, 0.3gN/kg, 0.5gN/kg) on biomass production, totle nitrogen, nitratereductase activity, nitrate content and water use efficiency in maize planted in pot. Themain results are showed as follows:1 The biomass production, nitrogen content, water use efficiency were influenced bynitrogen forms. Increasing the amount of NH₄⁺ -N and NO₃^- -N might enhance nitratecontent and nitrogen assimilation in maize seedlings. It was higher than the other threenitrogen forms in yield of above-ground and root, amount of nitrogen, water useefficiency. Nitrogen forms had little influence on totle nitrogen content. The nitrate ofNaNO₃ treatment was significantly lower than the other three nitrogen forms. Thisphenomenon may be related to the higher nitrate reductase activity by supplying NANO₃.2 The nitrate reductase activity of maize leaves and root were influenced by nitrogenforms. Whatever nitrogen content was, the order of nitrate reductase activity in maizeleaves displayed as: NH₄Cl＞NaNO₃＞NH₄NO₃＞Urea. The nitrate reductase activity ofmaize leaves was significantly higher at 0.1gN/kg by supplying NH₄Cl, while at 0.3gN/kgand 0.5gN/kg the NH₄Cl and NaNO₃ treatments were higher, but there's no significantdifference between them. The nitrate reductase activity of maize leaves was the highest bysupplying nitrate whatever the water content was. When water content at 13.2%, 17.6%,the nitrate reductase activity of maize root was higher by supplying NH₄NO₃. The nitratereductase activity of maize leaves and root was higher by supplying NaNO₃ than others.3 The biomass production, nitrogen content, water use efficiency were influenced bynitrogen amount. The absorption of nitrogen was increased with the increasing of theapplication of nitrogen fertilizer, which displayed in the high contents of nitrogen, totlenitrogen uptake and water use efficiency. The biomass production in maize was increasedunder the appropriate amount of nitrogen fertilizer, but it may reduced under theaxcessive irrigation and application of nitrogen fertilizer, espacially in ammoniumchloride and Urea. With the increasing of application of nitrogen fertilizer, the nitratecontent of maize leaves was raised4 It played different trend of the nitrate reductase activity in root and leaves with theincreaseing of nitrogen content. The nitrate reductase activity of maize grown was increased and nitrate reductase activity of maize root was reduced. This phenomenonmight related to the transfer of nitrate nitrogen from root to leaves by increasing thenitrogen content. Besides high amount of NH₄Cl and NH₄NO₃, the ratio of root nitratereductase activity/leaves nitrate reductase activity was bigger than one, so the reduction ofnitrogen was mostly in root in the seedlings of maize.5 The biomass production, nitrogen content, water use efficiency were influenced bywater. The totle nitrogen, nitrogen absorbed and biomass production were increased withthe appropriate increasing of irrigation. Lower water content could promote the growth ofroot and increase the root-shoot ratio. The nitrate nitrogen was higher at water content8.8% by supplying NH₄Cl, NH₄NO₃ and Urea, while supplying NaNO₃ the nitratenitrogen reached the highest at 13.2%.6 With the irrigation of water, the nitrate reductase activity of maize root wasincreased and the activity of maize leaves was reduced. It showed that the reduction ofnitrogen was mostly in root in the seedlings of maize.