Abstract:

N use efficiency is varied in different rice genotypes. Therefore it is necessary to identify the physiological mechanism of N absorption and utilization in different rice genotypes in order to increase N use efficiency through rice cultivar improvement. In this research, a field experiment with 225 kg ha^-1 N fertilizer application was carried out in 2006 on the farm of Yangzhou University, Jiangsu province, China. Using twelve rice genotypes (6 N-efficient and 6 N-inefficient ) selected from 120 rice cultivars in 2004 and 2005 to investigate the characteristics of rice matter production and accumulation. Relationship between N use efficiency and indexes of rice matter production and accumulation also analyzed. Results showed that although there was no significant difference in number of tillers per unit ground area between two rice types with different N use efficiencies, the percentage of productive tillers of N efficient rice type was obviously higher than that of N inefficient rice type. The characteristics of rice matter production and accumulation at different growth stages and their correlations with N use efficiency revealed that, for N efficient rice type, the rice matter production and accumulation was steady in early growth period, a little in middle growth period and large in later growth period. That is to say the N efficient rice type had proper leaf area index (LAI), photosynthetic potential (PP), crop growth rate (CGR), and a superior matter accumulation before the critical stage of productive tillering, although its ratio of dry matter to the total accumulation in whole life was relatively low; the LAI, PP, CGR and dry matter accumulation were lower during the period from the critical stage of productive tillering to elongating; and an increased leaf area, photosynthetic potential and an accelerated crop growth rate resulting from better population quality after the stage of elongating. According to the research results, the different characteristics of rice matter production and accumulation could not only illustrate the diversity of N use efficiency in different rice genotypes, but also provide feasible regulation approaches to increase N use efficiency in rice production.

Key words: Rice, N use efficiency, Physiological mechanism, Matter production, Matter accumulation