Effects Of Nitrogen Rates On Grain Yield And Quality Of Wheat For Different End Uses And Its Physiological Basis

Effects of nitrogen rates on grain yield and quality of wheat for different end uses and its physiological basis were studied by using two different winter wheat cultivars, Gaocheng 8901 (strong-gluten) and Shannong1391 (weak-gluten). The study set three levels of fertilizer N application amount: N 120,240 and 360 kg/hm2 and it was carried out in pool culture at the experimental farm of Shandong agricultural university from 2003 to 2004. The main results as follows: 1. Effects of nitrogen rates on the photosynthetic and senescence characters of wheat for different end uses in the latter development period The content of chlorophyll, chlorophyll fluorescence, photosynthetic rate and protective enzyme system had significant difference between GC8901 and SN1391, and responded to N differently. Chlorophyll content of the two cultivars was increased by using reasonable N and decreased by using excessive N. The light energy conversion efficiency, potential activity of photosynthetic reaction center â…¡, the non-photochemical dissipation of excess light energy which resisted the damage on photosynthetic apparatus of environmental stress ,and activity of protective enzyme of SN1391 were improved with increased N. Its photosynthetic rate of flag leaves was improved and leaf senescence was delayed. But the respond of GC8901 to nitrogen rate was on the contrary, its photosynthetic rate of flag leaves decreased markedly with the increased amount of N. We thought the main reason of the phenomena was: the ear bearing tille ability of GC8901 was increased by using more N, so that the plant population of GC8901 was bigger. The individual plant of this colony became weaker. 2. Effects of nitrogen rates on carbon metabolism of wheat for different end uses The carbon metabolic characteristics of SN1391, which had more starch, was different from GC8901 (low starch content) markedly, and responded to the amount of N differently. The photosynthetic rate of SN1391 and its activity of SPS could be increased by Using reasonable N , so that the exported ability of flag leaves was increased, and its sucrose content of grain, the activity of SS were increased, so that the substrate of starch was increased. At the same time, with using of N the activity of ADPGPPase, SSS and GBSS were increased, which advanced the synthesis of grain starch of SN1391, but excessive N was not useful to starch. The influence of N to starch synthesis of GC8901, which had low content of starch, was just on the contrary. Its starch accumulation of single kernel was decreased with more N. From this study we found that there were significant positive correlation between the activity of SPS and photosynthetic rate of wheat flag leaves, from which we guessed that photosynthesis may feed toward back to the activity of SS. We also found that the synthesis of amylose was latter than amylopection and its accumulation was lower too. The results of this study suggested that ADPGPPase played a vital role in the biosynthesis of starch, the activity of SSS was positive correlated with the accumulation amount of amlylopection, and the activity of GBSS closely related to amylose accumulation. 3. Effects of nitrogen rates on nitrogen metabolism of wheat for different end uses There was great difference between GC8901 and SN1391 in the assimilation, accumulation and distribution of N. The activity of NR and free amino acids content of GC8901,s flag leaves were higher than SN1391 and increased by using more N. Increasing the using rate of N also promoted the N accumulation of plant body and accelerated the transportation of free amino acids and N to wheat grain, at last increased the protein content of grain. Using suitable N could increased the activity of NR and free amino acids content of SN1391, and increased its grain protein content with more transported N to it. The result also showed that both wheat protein yield and starch yield were improved with reasonable N rate. Grain protein content was improved, while the grain yield was decreased with excessive nitrogen. 4. Effects of nitrogen rates on grain quality of wheat for different end uses The results showed that wheat grain quality was mostly decided by genotype and...