| Oilseed Rape, as a significant oil crop with planting advantage, has aroused widespread concern increasingly. With the new oilseed rape variety springing up possessing high yield and high quality, low nutrient utilization efficiency has become a new bottleneck, which constrain the further development of oilseed rape production. Especially because of high nitrogen (N) demand and low utilization rate, the development of rape career are restricted. As a result, how to raise the N fertilizer efficiency has become a central issue in plant nutrition research area. In the whole plant growth and development period, phytohormones play a critical regulatory role in the process of physiological metabolism and morphogenesis. However, effect of phytohormones on N reutilization and N efficiency regulation were few reported in recently.The experiment was conducted by daubing solutions of different growth regulators such as auxin(IAA), cytokinin(6-BA) and abscisic acid(ABA) to rape pod with two rapeseed varieties(A and B) under normal and deficient N conditions. The effect of N reutilization and efficiency during later stages of rape and corresponding mechanisms were studied, aiming at revealing physiological mechanisms of N utilization efficiency in rape, and providing a scientific basis for improving N utilization efficiency in rape.The results of the yield, yield components and nitrogen physiological efficiency indicated that the growth regulators significantly increased the rapeseed yield, N physiological efficiency, single pod number and grain number per pod, but had little effect on weight of thousand seeds. Different growth regulators had different influences on above indexes. ABA mainly impacted on grain number per pod, while IAA and6-BA on the grain yield and plant pod number. The effect of each growth regulator on single index differed in rape variety difference and different N treatments. IAA exhibited optimized effect on nitrogen physiological efficiency in rape variety A under normal N condition, while6-BA had a good effect under N deficient condition. As to rape variety B, IAA exhibited best impact under normal and deficient N conditions. In addition, nitrogen physiological efficiency of biomass and grain yield in normal N condition was lower than that in N deficient condition. Comparing with the grain yield, yield components and N physiological efficiency of two N levels, we found that grain yield and plant pod number in normal N condition were higher than those in N deficiency, nitrogen physiological efficiency in normal N condition was lower than that in deficient N condition, and there were little difference in weight of1000-grain weight and grain number per pod at two N levels.The results of nitrogen transport ratio and transport volume showed that three kinds of growth regulators could increase the nitrogen transport ratio and transport volume to grain, and reduce the losses. But the effect of different growth regulators on them differed in applied N levels and different varieties. IAA could pose greater contribution to nitrogen translocation and redistribution in variety A, and ABA in variety B. This advantage, meanwhile, also exhibited in the aspect of low N loss. IAA had a greater contribution to two rape varieties under N stress. On the normal N application condition, the amount of nitrogen redistribution and its proportion toward seeds and siliques was larger than the results of N stress condition. And the breed A are higher than breed B in two N levels, but the difference was not significant.The activity of proteoltic enzyme (PE) and the glutamine synthetase (GS) in blades and the activity of glutamate z-oxoghitarate aminotransferase (GOGAT) in seeds were determined during the later growing period. The results suggested that three kinds of plant growth regulators, to some extent, could improve the activity of enzyme related to N transport. ABA could improve the activity of PE, and IAA is effective on the active of GS and GOGAT. Compared with IAA and ABA, the percentage of increasing activity by6-BA was lower. In general, the enzyme activity in normal N condition is lower than that under N stress condition, and the enzyme activity in breed A is higher than that in breed B.The contents of L-glutamine, free amino acid and soluble sugar in phloem juice were measured. The results showed that phytohormones could increase the contents of L-glutamine, soluble sugar and free amino acid to varying degrees. IAA and ABA are more beneficial in L-glutamine content, while6-BA is useful to soluble sugar. To the free amino acid content, the influence is different from varieties. Different levels of N and varieties had different effects on the content of phloem juice. The content of L-glutamine showed that the normal N application condition was better for its improvement than that under N stress condition, and the content in breed A was lower than that in breed B. The content of soluble sugar in breed A is slightly lower than that in breed B, but few differences between the two N levels. The free amino acid content in two N levels and two varieties are barely different.The determination of rapeseed oil and protein indicated that growth regulators could increase the grain protein content and protein content of rapeseed, but little effect in the oil content. However, because growth regulators increased the grain yield, the oil yield got significantly improved. The growing contribution of regulators in oil production improvement are varied. For breed A, on the normal N application condition,6-BA is better. However, ABA was more useful under N stress condition. For breed B, IAA is more effective in two N levels. The influences of N levels and rape varieties on grain protein and oil content were analysed. The protein content, protein yield and oil yield showed that normal N condition is better for its improvement than N stress, but oil contein is the opposite results. Breed A is higher than breed B in protein content, protein yield and oil yield, but the oil content is no difference between two varieties. |
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