Using indica hybrid rice Shanyou 63 and indica/japonica hybrid rice PC311/Zaoxiandang 18 as materials, the effects of exogenous polyamines on grain plumpness under water deficit stress were studied. Putrescine(Put) content in rice leaves and the ratios of Put to spermidine (Spd) as well as spermine (Spm) obviously increasedunder water deficit stress. After applying low concentration of Spd (1 mmol/L) or Spin (0. 5 mmol/L) at headingstage. Put and MDA (malonadehyde) content in the leaves decreased, while Spd and Spm content, photosyntheticrate, endosperm cells, plump-grain percentage and 1000-grain weight significantly increased.
