Nitrogen uptake, distribution by rice and its losses from plant tissues during

To determine the nitrogen uptake, distribution and N losses from plant tissues at various growing stage by rice plant, solution culture experiments using ()~(15)N tracer technique was conducted at IRRI in Philippines. The results showed that the total nitrogen uptake at panicle initiation (PI) was significantly greater than that at mid-tillering(MT) stage; (()~(15)N) was mostly distributed to rice leaves at MT, and only 39% of ()~(15)N which being absorbed at MT was transmitted to grains at maturity; ()~(15)N was mostly distributed to stems and leaf-sheathes at PI, and 46% of ()~(15)N uptake at PI was transmitted to grains at maturity; According to the ()~(15)N balance at maturity, it was found that the losses of nitrogen from plant tissues were 16.7% and 13.4% while ()~(15)N absorbed at MT and at PI separately, in the duration from ()~(15)N labeling to maturation.