Effects Of Day And Night High Temperature On Spikelet Development And Grain Filling In Rice

The intensification of climate change has led to unstable weather changes during the rice growing season,with the occurrence of frequent extreme weather and frequent high temperature heat hazards.In recent years,climate change has also led to an increase trend in nighttime temperatures,with the difference in temperature difference between day and night in different parts of the middle and lower reaches of the Yangtze River.At present,a lot of research had been done on the effects of daytime temperature increase on panicle development,flowering and fruiting,grain filling and other aspects of rice by Scholars at home and abroad,however,there is little research on the effect of temperature difference on rice growth and development with the increase of day and night temperature.Based on this study,the effects of day and night high temperature and temperature difference on the development of rice glume and grain fruiting were studied.Pot and field planting methods were used in this study.The effects of high temperature and diurnal temperature difference on flowering habits,spikelets,grain filling and material accumulation in rice and their physiological mechanisms were studied.At the same time,the effect of temperature and light of different sowing date on grain fruiting under field condition was studied.In order to provide a reference for the middle and lower reaches of the Yangtze River rice disaster reduction and conservation and evaluation of heat tolerance of rice varieties.The main results were as follows:1.The effects of elevated night temperature at flowering stage on flowering habits and fertilization and fruiting of glumes in rice were studied.The results showed that the flowering period of rice was earlier and the pollen vigor was gradually decreased by the increase of night temperature.When the night temperature increased by 4 ℃ and 8 ℃,the percentage of pollen vigor of Huang Huazhan decreased by13.6 and 17.6 percentage points respectively,the percentage of Huang Sizhan by 1.1 percentage points and the percentage of Huang Sizhan decreased by 4.5 percentage points,the decrease in the pollen vigor of Huang Huazhan was more obvious than that of Huang Sizhan;The increase of night temperature significantly decreased the rate of anther dehiscence,and the longer the duration,the greater the effect.The increase of night temperature resulted in the decrease of seed setting rate and the decrease of Huang Huazhan percentage was larger than that of Huang Sizhan percentage.The main reason for the decrease of seed setting rate was the decrease of anther opening rate and pollen vigor.The effects of elevated night temperature at flowering stage on flowering habit and fertilization and fruiting of glumes in rice were studied.2.The temperature increase of day and night,especially the increase of night temperature,the main factor affecting the yield was the decrease of 1000-grain weight and seed setting rate;with the increase of night temperature during the filling stage,the grain filling was accelerated,and the dry weight of the ear was decreased;The night temperature rised,and the assimilation products stored in the leaves and stem sheaths cannot be transported normally.3.The effects of night temperature on starch and sucrose contents and enzyme activities in rice grains during grain filling were studied..The activities of starch and sucrose metabolism-related enzymes in rice grains were significantly affected by the increase of night temperature in 0-10 ds and 10-20 ds afterflowering,and among of them,0-10 d was the most sensitive period of night temperature change of starch metabolism.The increase of night temperature in the early stage of grain filling increased the starch content,and the content of straight and amylopectin also increased with it,and the decrease occurred in the content of sucrose,the decrease in activity of sucrose synthase and soluble starch synthase and starch branching enzyme,and the activity of sucrose phosphate synthase increased in the day and fell in the night.The increase of night temperature affects the enzyme activity of the four enzymes and has a continuous effect,indicating that the enzyme activity is affected by the increase of night temperature at the same time.4.Through the staged sowing adjustment and sowing date changing the filling period as well as the study of the day and night temperature,it showed that: the highest temperature of Huang Huazhan was32 °C during the filling stage,with the lowest temperature of about 21 °C.The selection of suitable sowing period could increase the rice quality of the grain,with significantly increasing the brown rice rate,the polished rice rate,the whole polished rice rate,length-width ratio,gel consistency,amylose content,reduced chalkiness,chalky grain rate and protein content.