Difference On Nitrogen Utilization And Its Physiological Basis Of Rice Varieties With Diverse Plant Types

The average nitrogen use efficiency of rice is only 35% in China. The low nitrogen use efficiency not only result in the waste of resources, increased production costs, but also lead to a series of environmental and healthy problems. Therefore, studies on nitrogen use efficiency and the mechanism of the differences on nitrogen utilization of different varieties play an important role. The compact rice Shennong 07425 with erect panicle and the loose rice Akihikari with curved panicle were used to study the differences on nitrogen utilization and its physiological basis under several nitrogen levels in pot experiment. The main results are as follows.1. There is significant difference on N2O Flux between the tow varieties. The nitrification-denitrification gas loss in Shennong 07425 is far less than that of Akihikari. N2O Flux of different plant species changes with different nitrogen levels, the N2O Flux in Shennong 07425 increases with increasing nitrogen application, and it reaches the maximum under high nitrogen treatment. But Akihikari attains its maximum under middle nitrogen treatment. The interaction of variety and nitrogen level affect N2O Flux greatly, relatively speaking, N2O Flux is mostly decided by nitrogen level than variety.2. The number of nitrifying-denitrifying bacteria in soil is significantly different between the tow varieties. The number of nitrifying bacteria in the compact variety Shennong 07425 is much larger than that of Akihikari, but only the number of denitrifying bacteria under middle and high nitrogen treatment is significantly greater than the loose variety Akihikari.The number of Nitrifying-denitrifying bacteria of different plant species changes with different nitrogen levels. The number of Nitrifying-denitrifying bacteria in Shennong 07425 increases with increasing nitrogen application. It raises crosscurrent on the number of nitrifying bacteria in the loose variety Akihikari, the CK treatment attains the maximum. The CK treatment handles the largest number of denitrifying bacteria in Akihikari, and it still in line with high nitrogen> middle nitrogen> low nitrogen level.3. The increasing application of nitrogen fertilizer enhance plant height,number of tillers,chlorophyll content(SPAD value) and leaf area per plant within a certain range. Total length of root in Shennong 07425 decreases with nitrogen level raised, but it reaches the maximum in high N level in Akihikari. The total length is mainly affected by plant type.It appears similar result on dry weight and root volume between the two varieties, all magnify with increasing levels of nitrogen fertilizer.4. NO3- content, NO2- content, NH4+ content, nitrate reductase activity in leaves of both rice increases with elevated levels of nitrogen. Soluble protein content under the high nitrogen treatment reflects significantly higher than the middle and low nitrogen treatment of both. And the proline content, relative conductivity, soluble sugar content under High nitrogen, low nitrogen treatment show significantly greater than that in middle nitrogen level. MDA content in leaves of two varieties elevate with the gradual increase of aging, and it shows that MDA content among treatments for low nitrogen, high nitrogen are bigger than that in middle nitrogen level. The CAT activity, POD activity, SOD activity among these treatments reveal that high nitrogen is greater than middle nitrogen and middle nitrogen is larger than low nitrogen treatment.5. NO3- content, NO2- content, NH4+content, nitrate reductase activity in root of both rice increases with elevating levels of nitrogen. NO3- content of the two varieties appears extremely significant difference in the fullheading stage. The growth of NO2- content in Shennong07425 is smaller than Akihikari after jointing stage. The NH4+ content changes with the growth stage differently between the two varieties. Compact and loose Shennong 07425 total absorption area of root Akihikari active absorption area, root oxidation, reducing power as the nitrogen level increases. There is the same trend of root total absorption area, active absorption area, oxidizing ability per gram between Shennong 07425 and Akihikari:nitrogen level is bigger, the items become stronger.6. Nitrification intensity of soil in Shennong 07425 increases with nitrogen level, but it reaches the maximum in low nitrogen level in Akihikari. There is the same trend of denitrification intensity between Shennong 07425 and Akihikari:nitrogen level is bigger; the denitrification intensity became stronger. The denitrification intensity is chiefly decided by nitrogen level. The compact variety Shennong 07425 reaches the largest soil nitrate reductase activity in jointing stage, Akihikari is in tillering stage, and soil nitrate reductase activity has large difference between varieties. Soil nitrate reductase activity of two varieties increases with the growing nitrogen level. Urease activity under the middle nitrogen treatment reflects significantly higher than the high and low nitrogen treatment.Total reducing substances of Shennong 07425 increases with the growing nitrogen level. Total reducing substances of Akihikari under the high nitrogen treatment reflects significantly higher than the middle and low nitrogen treatment. The active reducing substances of Shennong 07425 get larger with the increasing nitrogen level, but nitrogen application has no obvious effect to active reducing substances of Akihikari. There is no significant difference of total nitrogen content between the two varieties. Total nitrogen content of two varieties increases to a certain extent with the growing nitrogen level.7. Grain yield of compact variety Shennong 07425 and loose variety Akihikari increases significantly with the growing nitrogen level. The panicles indicate significant difference between species, and it in line with high nitrogen> middle nitrogen> low nitrogen level. The full-grain percentage exposes significant difference between species, grain number of per ear and 1000-grain weight reveal extremely significant difference between the two species.Nitrogen grain production efficiency of Shennong 07425 follow the low nitrogen> middle nitrogen> high nitrogen trends, and it has significant differences among treatments. Nitrogen grain production efficiency of Akihikari under the middle nitrogen treatment reflects significantly higher than the high and low nitrogen treatment. Nitrogen harvest index and nitrogen partial factor productivity of two cultivars are in line with low nitrogen> middle nitrogen> high nitrogen.