Daylength Measurements by Rice Plants in Photoperiodic Short‐Day Flowering

Plants set seed at appropriate seasons. One major mechanism responsible for this adaptation involves photoperiodic flowering. Most plants are classified as either long-day plants, which flower under a longer photoperiod, or short-day plants, which flower under a shorter photoperiod. A third group, day-neutral plants, is not responsive to changes in photoperiod. During the past decade, molecular analysis has revealed at the molecular level how the long-day plant Arabidopsis thaliana measures daylength in photoperiodic flowering. In contrast, the molecular mechanisms underlying the responses of short-day plants are still under investigation. Progress in understanding photoperiodic flowering in rice (Oryza sativa), a short-day plant, revealed unique, evolutionarily conserved pathways involved in photoperiodic flowering at the molecular level. Furthermore, the conserved pathways promote flowering under short-day conditions and suppress flowering under long-day conditions in rice, but promote flowering under long-day conditions in Arabidopsis. In this chapter, we discuss the molecular mechanisms responsible for short-day flowering in rice in comparison with long-day flowering in Arabidopsis.