Abstract: Worldwide warming climate is causing more and more disadvantages for farming. A better understanding of high temperature stress on rice production is necessary for sustainable agriculture. In present study, eight leading hybrid rice combinations were selected to study the physiological and morphological adaptability to 40℃ air temperature stress. Heat treatment was conducted by 6 h each day from initial heading through 15 days. Guodao 6 and Xieyou 46 showed significant differences in response to high temperature stress during flowering period, and were selected to do further study on their flowering and grain-setting characteristic to high temperature stress. It was observed that Guodao 6 showed a relative stability in grain setting under high temperature stress. This may be associated with its adaptability to heat avoidance, displaying flowering period shortened and “Apical grain superiority” weakened, as well as flowering clock decentralized and the flowering peak value decreased. Daily number of spikelet flowering increased and flowering clock delayed for 2 hours during initial heading period.

Key words: High temperature stress, Heat tolerance, Hybrid rice, Flowering clock, Glumes opening rate