| Among the elements required by plant, nitrogen is the largest one, and at the same time it is a limited factoring the signal plant ,natural ecosystem and artificial ecosystem. The experiment of water culture and sand culture were carried out with different crop such as wheat, corn and sunflower to study effect of nitrogen and N form on the yield and physiological characteristics, we also devise the field experiment to search the relationship between NR activity of different genotype and its mass, yield and protein content of kernel. The aim is to supply the evidence for optimum and scientific fertilizer. The results as follows:I.We accomplished the water culture of winter wheat from regreen梛oints stage to matured stage, we harvested the wheat. The ultimate reason of N rate affecting the growth of wheat is that it affected the water content of wheat tissue.Water culture experiment was carried out with winter wheat ( Triticum aestivum) at the tillering stage to study the influence of nitrogen rates on some nitrogenous substances and water content . The results showed that with the increase of N rates, the content of endogenous nitrate, the soluble protein were all increased in leaf and root. The content of chlorophyll per plant increased with the increasing of the N rate, there was a biological dilution phenomena about the content of chlorophyll. N rate affected the water content. Because N rate influenced the nitrogenous substances and water content, so it led the remarkable difference in leaf area per plant, fresh weight and dry weight of root and shoot .The conclusion was that supplying the optimum N rate, water content of wheat was higher, biomass was higher, too.We accomplished the life-cycle of winter wheat from regreen-joints stage to matured stage adopting methods of water culture. At the stage of reproduction, supply the different N rate lasting 15 d to study the influence of that one on the some physiological characteristics and biomass. The results showed as follows: with the increasing of exogenous N rates, the leaf area, the photosynthetic rate and the content of chlorophyll were all enhanced: In the condition of supplying deficient nitrogen rate, the content of DNA of root and leaf was increased. It had the remarkable impact on the biomass and yield of wheat when supplying the deficient nitrogen rate at the booting stage.2. Dicotyledon and monocotyledon had different response to the nitrogen stress. Two kind of crop were cultivated at different N concentration (Hoagland solution, l/3NHoagland solution, l/9NHoagland solution) under sand culture. The results showed that: at low N concentration, membrane permeability, activity of root systemincreased while water consumption, amount of N uptake, activity of NR and amount of free ammonia acid decreased; supplying the lower nitrogen, the water consumed decreased, but water use efficiency (WUE) was increased. Compared the crops, nitrogen deficient had grater effect on monocotyledon than on dicotyledon.3. The different crop had the different response to N form. The rate of NH/桸 to N03桸 was 50:50 was the optimum proportion for wheat growth. Nitrate N was the better form for corn seedling growth.Nitrogen form had a remarkable effect on the physiological characteristics and yield when treated wheat with different N form at the stage of vegetation and reproduction growth being conducted together. Solution culture experiment was carried out with winter wheat (Xiaoyan 22) as an indicator crop to study the influence of different form of N on the nitrogenous compounds in leaf and root and on some physiological characteristics at the stage of the vegetative and reproductive growth being conducted together, and different ratios of ammonium N to nitrate N as well as sole urea were adopted in solution for this purpose. The results showed that when the ratio of NO"3-N to NHVN was 50 I 50, the leaf area was largest, and the chlorophyll, root activity was the highest in all treatments. Consequently, this ratio resulted in higher shoot and grain yie...
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