Full Length Article

Sink size with spikelets number (m-2) is one of the critical factors determining grain yield in cereals including rice. Nitrogen and dry matter are regarded as the two main factors controlling the formation of sink size and the objectives of present study were to examine the potential mechanisms underlying the difference in sink size between the late maturing YLY6 and HY3 an early maturing and drought resistant variety. The difference in the contribution of N and dry matter to the formation of sink size between the two varieties was also investigated. Growth duration of YLY6 was 20 days longer than of HY3. YLY6 produced significantly larger sink size than HY3 due to more secondary branches and spikelets, which resulted in higher grain yield for YLY6. Application of N fertilizer increased spikelets number for both YLY6 and HY3. Sink size of HY3 significantly correlated with N accumulation from mid-tillering (MT) to panicle initiation stage (PI) (R2=0.68) and N concentration in stem at PI (R2=0.74). However, for the late-maturing variety-YLY6, formation of sink size was more associated with biomass accumulation from PI-FL (flowering, R2=0.82). Both N and biomass accumulation significantly contributed to the difference in sink size between HY3 and YLY6, with R2 of 0.45 and 0.84, respectively. Taken together, this study indicated tha