| Wheat(Triticum aestivum L.)is one of the most important staple crops in China,and its yield is very important to ensure China’s food security.As a cool-loving gramineous crop,the suitable temperature range of wheat growth is 10-24℃.After the suitable temperature range,every increase of 1℃ will cause the average yield loss of about 6% of wheat in the world.Heading stage and flowering stage are very important for the formation of wheat yield.Extreme weather occurs frequently in this period,and high temperature stress is easy to affect the reproductive growth and grout setting of wheat,resulting in double loss of yield and quality.In recent years,the problem of global warming is more and more serious,wheat reproductive development stage faces more severe challenges of high temperature.It was also found that high temperature stress in the ovules of wheat at reproductive growth stage leads to accumulation of stress signaling molecule Nitric oxide(NO).Excessive NO inhibits the transport of auxin from the mother to the female gametophyte,which in turn affects wheat yield.Experiments in Arabidopsis thaliana show that exogenous auxin can properly restore the effect of heat stress on seed setting.On this basis,experiments were carried out in wheat to systematically analyze the effects of high temperature stress on wheat yield and quality,and explore whether exogenous auxin can improve the effects of heat stress on wheat growth and development.In this study,the effects of high temperature on wheat growth and yield were analyzed based on the meteorological data and agronomic characters of four environmental types of 406 wheat population materials collected in the laboratory.After that,9 wheat materials with the same heading and flowering dates were selected,and field greenhouse experiments were carried out from heading to flowering to simulate high temperature stress.At the same time,the experimental materials were sown in normal sowing period(early October of the same year)and late sowing period(mid-January of the next year).Exogenous auxin was sprayed with different concentration gradients of 0 n M,1 n M,10 n M and 100 n M from heading stage to flowering stage.Finally,the panicle characters(panicle length,spikelet number,fertile spikelet number,grain number per panicle,total floret number),grain characters(grain length,grain width,1000-grain weight),yield characters(moisture content,protein content,settlement value)were investigated.The objective was to clarify the influence of high temperature on wheat heading and flowering stage,and to explore a suitable auxin application mode to improve the damage caused by heat stress on wheat,so as to ensure food security and provide theoretical support for dealing with future climate change.The main results of this study are as follows:1.The average temperature and growth days of wheat at different growth stages in two sowing periods(normal sowing and late sowing)in 2019-2020 and 2020-2021 were investigated.It was found that the total growth period of normal sowing wheat was about 250 days,and that of late sowing wheat was about 170 days.From heading to flowering,the average temperature of late sowing was 11.7℃ higher than that of normal sowing.Late sowing significantly shortened the growth period of wheat and increased the average temperature in the growth stage after emergence,among which the high temperature stress was the most significant at heading and flowering stage.2.Through the investigation of yield traits(plant height,total tillering number and 1000-grain weight)of 406 materials in two sowing periods from 2019 to 2020 and 2020 to 2021,it was found that the average yield per plant of late sowing wheat was reduced by 36.4 g compared with that of normal sowing wheat,indicating that late sowing had an impact on wheat yield.Further statistics of spike characters(number of spikelets,number of fertile spikelets,number of grains per spike)showed that compared with normal sowing wheat,the average number of fertile spikelets per spike of late sowing wheat decreased by three,6.5grains per spike.The yield per plant of wheat decreased significantly after late sowing,and its effect on fertile spikelet and kernel number per spike was the main factor leading to the decrease of wheat yield.3.Nine wheat materials with the same heading and flowering dates were screened based on the fertile spikelets of wheat of two sowing periods in two years.Greenhouse warming from heading to flowering and simulated high temperature stress of late sowing were carried out on them.Through the investigation of panicle traits,grain traits and quality traits,the analysis showed that compared with normal sowing,late sowing resulted in an average decrease of 1 cm spike length,2 fewer spikelet,11.7 less kernel number per panicle,7.8 g less thousand grain weight,0.23% less grain water content,2.5% increase in grain protein content.However,after warming the greenhouse,the number of spikelets decreased by 2 and the number of grains per spike decreased by 6.3 g,which had no significant effect on the characters of spike length and grain water content.4.Wheat materials from heading to flowering stage were treated with exogenous auxin at 0 n M,1 n M,10 n M and 100 n M to investigate the spike characters,grain characters and quality characters of wheat.Analysis showed that 10 n M NAA treatment increased 0.3spikelets and 3 grains per ear.Auxin with different concentration gradient had no significant effect on grain character and quality character.5.From heading to flowering stage,exogenous auxin of 0 n M,1 n M,10 n M and 100 n M was used to treat the experimental materials of normal growth,greenhouse warming and late sowing,and investigate the ear characters,grain characters and quality characters of wheat.The results showed that after 10 n M auxin treatment,the seed setting rate of wheat material increased by 6.1% on average in greenhouse warming and 8.4% in late sowing.After 100 n M auxin treatment,the average seed setting rate of wheat in greenhouse warming increased by5.9%,and that of late sowing wheat increased by 5.6%.Exogenous auxin applied at 10 n M and 100 n M significantly increased the grain yield of wheat ears.Auxin treatment at 10 n M significantly improved the decrease of grain number per ear and seed setting rate caused by heat stress,thus increasing wheat yield,but did not improve the loss of grain weight and quality. |
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