Difference Of Physiological Properties Among Rapeseed Genotypes With Varied Nitrogen Use Efficiency

Application of a large amount of nitrogen not only can cause environment pollution, butalso can reduce nitrogen use efficiency (NUE) of rapeseed. Breeding of high NUE rapeseedcultivars could be a very good approach to decrease nitrogen loss. Screening of different NUEcultivars and finding out the differences of their physiological metabolism are important.High-NUE-genotypes and low-NUE-genotypes which were screened out by our researchgroup were used to study the differences of root physiological properties, photosynthesis,shoot physiological properties and root exudates in different nitrogen forms and phosphorusstress condition by hydroponic experiment. The main results were as follows:1. Low-NUE-genotypes had greater biomass, higher root activity, net photosynthetic rate,SPAD value, higher nitrate reductase activity, glutamine synthetase activity, glutamatesynthase activity and higher nitrogen and phosphorus content at vegetative growth stage thanthat of high-NUE-genotypes, no matter NO3-or NH4+was the only N resource in solution.When NH4+was the only N resource, the differences of these indexes betweenhigh-NUE-genotypes and low-NUE-genotypes was greater than that of NO3-treatment.High-NUE-genotypes secreted more alkanes when NO3-was the only N resource, whilelow-NUE-genotypes secreted more alkanes when NH4+was the only N resource.2. Low–NUE-genotypes had greater biomass, higher root activity, net photosynthetic rate,nitrate reductase activity, glutamine synthetase activity, glutamate synthase activity andhigher nitrogen and phosphorus content at vegetative growth stage than that ofhigh-NUE-genotypes, no matter low P concentration or normal P concentration was supplied.High-NUE-genotypes secreted more root exudation than low-NUE-genotypes at normal Psupply. Under P stress, all testing genotypes could mainly secrete more root exudation.However, low-NUE-genotypes had much increase of exudation than that of high-NUE-genotypes. Low-NUE-genotypes could secrete more organic acid under P stress. Theseorganic acids may dissolve more insoluble P to adapt phosphorus deficiency.Research results above establish basis for finding high NUE rapeseed genotypes,revealing the mechanism of crops to efficient use of nitrogen and improving crop nitrogennutrition traits finally.