2.4 Sampling
Rice superior spikelets (located at the upper 1/3 of the rice panicle) flowering on the same day were tagged and sampled at 9:00 am on the 3rd, 6th, 9th, 12th and 15th day after flowering. The collected spikelets were immediately frozen in liquid nitrogen and stored at -80 ° for further analysis. All samples collected from the ET treatment were within the effective warming area (Figure 1). At the mature stage, 10 holes were randomly selected from each plot, and the number of spikelets per hole, the number of spikelets per panicle, 1000-grain weight, seed setting rate were investigated to calculate the final yield. Harvested spikelets were air dried under natural conditions for the determination of starch and protein content.