Photoperiod-sensitive genic male sterile rice (PSGMSR) has the characteristics that its pollen fertility is regulated by photoperiod; it is completely sterile under long-day conditions but fertile under short-day conditions. PSGMSR has now been widely used in two-line hybrid rice breeding. Despite extensive studies on various aspects of the PSGMSR, the leaves and the sites where photoperiod response occurs to induce fertility change is unknown. In this study, we investigated the sites of response by examini...