Wang YuLong

General characteristics of nitrogen uptake and utilization in conventional indica rice cultivars with different panicle weight types.

A total of 88 and 122 conventional indica rice (Oryza sativa L.) cultivars with different types of panicle weight (PW) were solution-cultured in 2001 and 2002, respectively. On the basis of PW, these cultivars were classified into 6 types from low to high (i.e. A, B, C, D, E, and F, A was the lowest, F was the highest). Dry matter weight and nitrogen content of roots, culm and sheath, leaf, and panicle were measured at heading and maturity stages, and the grain yield and its components were tested after harvest. No significant difference in nitrogen content of the plant was detected between various PW types of conventional indica rice. The population nitrogen accumulation (NA) and individual NA at heading, grain filling and maturity stages were higher in cultivars with large PW than in cultivars with small PW. The effects of individual NA and panicles per area on population NA were both significant, especially the individual NA at heading stage. In cultivars with medium to large PW, nitrogen harvest index and nitrogen use efficiency for grain yield (NUEg) were higher than those in other rice types. And rice cultivars with large PW showed longer growth duration especially days from sowing to heading. The effects of NA and NUEg on PW were both signifi- cant, while the NA was more effective. The N uptake intensity of population especially N uptake intensity of individual was the main factor influencing N accumulation levels of population and individual in conventional indica rice cultivars.