DESICCATION TOLERANCE AND POTENTIAL LONGEVITY OF DEVELOPING SEEDS OF RICE (ORYZA-SATIVA L)

The longevity and desiccation tolerance of samples of seeds of a japonica rice (Oryza sativa L.) harvested serially during development from plants grown in two temperature regimes, viz 28/20°C and 32/24°C (12/12 h) were determined. Mass maturity (defined as the end of the seed-filling phase) occurred 19-7 and 18-3 d after 50% anthesis, respectively. Longevity (determined at 40 °C with 15% moisture content and quantified by the value of the constant Ki of the seed viability equation) improved during seed development and maturation until 17 and 14 d after mass maturity in the cooler and warmer regimes, respectively, but declined thereafter. Changes in Ki with time were similar in the two environments until mass maturity, but the increase in Ki values after mass maturity was much greater in the cooler regime. Tolerance of desiccation to low (4%) moisture contents improved until 22 and 14 d after mass maturity in the cooler and warmer regimes, respectively, when maturation drying had reduced seed moisture contents naturally to 24 and 32% moisture content, respectively. Further delays to seed harvest reduced desiccation tolerance, particularly in the warmer environment. Comparison among 15 samples of seeds harvested at different times in the two environments showed a strong correlation (r = 0'947, P <0.01) between longevity (Ki) and desiccation tolerance (to 4% moisture content). Hence, it is suggested that the regulation of desiccation tolerance to low moisture contents and potential air-dry longevity during seed development and maturation determined here may have a common cause. © 1994 Annals of Botany Company.