Response to Photoperiod of Reported Long-day and Intermediate Varieties of Rice

Abstract

ALTHOUGH Oryza sativa L. is generally considered to be a short-day plant, a delay in flowering by short-day treatment has been reported1–7. Varieties with such a response would have a potential use in studies of physiology and breeding, and would be most interesting ecologically. The data reported on such varieties do not present a clear picture of their reaction, however, and are insufficient to warrant their classification as intermediate, much less long-day, types. To clarify this point, we have carried out detailed tests on several varieties of rice previously reported to be long-day or intermediate. ‘BPI-76’, a variety known to be sensitive to photoperiod, was included as a control.