Differences in the effects of dehusking during formation of seeds on the germination of seeds of indica and japonica rice (Oryza sativa L)

Differences in germination of intact and dehusked seeds of two japonica and two indica cultivars of rice (Oryza sativa L.) were examined during the development and maturation of seeds both under high-temperature (30/23 degrees C) and low-temperature (20/13 degrees C) regimes and a 14-h photoperiod in growth cabinets. As described previously for seeds grown in the paddy fields, germination of freshly harvested japonica rice seeds that developed and matured in growth cabinets was inhibited by dehusking. We observed a roughly consistent triphasic pattern with respect to the germination of intact and dehusked seeds during the development and maturation of seeds of indica and japonica rice. The triphasic pattern consisted of: (a) an initial phase, during which germination was stimulated by dehusking both in indica and japonica rice; (b) a second phase during which almost no dehusked seeds of indica or japonica rice germinated; and (c) a third phase during which intrinsic differences between indica and japonica rice were observed, with dehusking stimulating germination of indica rice but inhibiting that of japonica. Temperature regimes did nor affect this triphasic pattern, but the time from the day of anthesis to mass maturity was affected by temperature regimes, and the effect was more pronounced in indica than in japonica rice. (C) 1996 Annals of Botany Company.