Role of nitrogen regulation in sink and source formation of high-yielding rice cultivars

Abstract

By applying nitrogen (N) and phosphorus (P) fertilizers at different rates and times to high-yielding rice cultivars, we analyzed the absorption of N at different stages in relation to the formation of the source and sink as well as grain yield. The results showed that, the grain yield increased along with the enlargement of the sink size. N absorption from 30 d before heading (DBH) to heading was more important for enlarging the yield sink than that at other stages. N absorption during this period was even more important for panicle weight type cultivars (line 9004 and Yangdao 4) than that for a panicle number type cultivar (Suweon 258). N absorption before 30 DBH led to a higher increase of the leaf area index (LAI) compared to that afterwards. And faster decrease of LAI after heading was correlated more closely with the LAI at 30 DBH than with the LAI increase from 30 DBH to heading. A larger N absorption from 30 DBH to heading enabled to maintain a higher LAI after heading. Dry matter accumulation after heading contributed more to grain yield than that at heading in the panicle weight type cultivars, whereas it was equally important in the panicle number type cultivar. Regulation of N absorption at different growth stages of high-yielding rice cultivars was also examined.