Studies On The Mechanism Of The High Nitrogen Efficiency In Oilseed Rape

By improving crops nitrogen use efficiency to increase crops yield,save the resource and improve the quality of environment, it is necessary for the sustainable development of china, and it is the basic important problem of science for the field of the agricultural resource and environment to solve too. The nitrogen use efficiency (NUE) is the adaptable ability in the process of the growth of plants to adapt the nitrogen supply of the soil, including the uptake efficiency and utilization efficiency (UPE and UTE ) .It is the number of characters controlled by many genes.Therefore,it will be showed by a series of morphological, physiological and biochemical characteristics. And the physiological mechanism of plant is the hot spots of plant nutrition.Greenhouse experiment was carried out at the experimental station of Hunan agricultural university in 2006-2007. Using sand experiment,study the physiological mechanism of nitrogen of three oilseed rape cultivars under two levels of nitrogen (normal supply of nitrogen and half of normal supply of nitrogen) .The results showed as follows:1. The studies of the physiological mechanism of high nitrogen efficiency found that, there are differences of UPE under the two levels of nitrogen for the cultivars of the same genotypes , Under the threatening supply of nitrogen ,the high NUE cultivar A13 had high UPE and UTE, so the contribution of UPE and UTE to the NUE of oilseed rapes was large. Under the normal supply of nitrogen,the differences of UPE were not significant while the differences of UTE were obvious,and it was consistent with the change trend of NUE, so the contribution of UTE to the NUE of oilseed rapes was large.2. The studied results to the physiological mechanism of high efficiency to uptake nitrogen showed that: Under the threatening supply of nitrogen ,the cultivars of high UPE had larger dry weight of roots, more first-class lateral roots, and higher vigor of roots, Under the normal supply of nitrogen, the cultivars of high UPE had larger dry weight of roots,more first-class lateral roots,and higher vigor of roots at the flowering stage.3. The studied results to the physiological mechanism of high efficiency to utilize nitrogen showed that: Under the threatening supply of nitrogen , The cultivars of high UTE had higher yield of seeds,higher photosynthesis rate of leaves at seeding stage and siliquing stage, nitrogen decreased amount of leaves,sterns and roots at the growth at later stage and the transferring amount and its proportion of nitrogen absorbed to seeds were larger at all growing stages, while nitrogen loss amount and its proportion from all stages to harvest was less than other cultivars. Under the normal supply of nitrogen, The cultivars of high UTE had higher yield of seeds and dry matters,higher photosynthesis rate of leaves at seeding stage and siliquing stage,the re-used nitrogen amount of nitrate was larger, nitrogen decreased amount of leaves was larger at later stage,and nitrogen decreased amount of stems and roots was larger at early stage,but nitrogen loss amount and its proportion from seeding stage to harvest was less than other cultivars .