Daylength responses of various morphogenetic events after panicle initiation in late japonica rice (Oryza sativa L. ssp. japonica)

Plant morphogenesis is an intimate cooperation between environmental signals and a genetically-encoded developmental programme. Although all stages subsequent to floral induction may be influenced by daylength, the information available has come from diverse species during different morphogenetic events. This makes it difficult to investigate how photoperiodic signalling is integrated into various steps of the developmental programme. Here, we report that, in late japonica rice lines, morphogenetic events, including 12th leaf, axis of the main panicle, awn of the glum, anthers, elongation rate of internodes, and pollen fertility of the photoperiod-sensitive genic male-sterile (PGMS) rice, are significantly affected by daylength after panicle initiation. These data indicate that daylength affects many morphologic events, and that changes in morphology are mainly determined by the characteristics of the events themselves. These findings lay a foundation for future investigations into how potentially common photoperiodic signalling system(s) are integrated with diversified developmental events. In addition, we discussed the essential nature of PGMS rice.