A study on the photoperiodic control of flower in rice is advancing and rice has become an of short day plant. Many genes used in flowering time determination in rice have been identified by many methods. The conclusion from these molecular studies is a remarkable conservation of genes which play an important role in the control of flowering time in rice. The rice photoperiod sensitivity gene Hd3a was originally detected as a heading date related quantitative trait locus found on chromosome 6 of rice. High resolution linkage mapping of Hd3a was carried using a huge segregating population derived from advanced backcross progeny between a japonica variety, Nipponbare, and an indica variety, Kasalath. Researchers revealed that there are three (3) pathways for the day length regulation of flowering in rice, short day activation pathway and long day suppression pathway lastly the long day activation pathway. Some genes where used in multiple pathways and others are specific to a particular pathway. There regulation also depends on the developmental stages. Rice may be an ideal plant to study the night break effect on flowering. In the near future there is need for better understand the controlled of flowering in rice at the genetic level.