The Effects Of Increasing Temperature During Late Winter And Early Spring On Grain Yield And Quality Of Winter Wheat

In order to explore the effect of climate warming characterized by asymmetric warming on wheat yield and quality in North China Plain.In this study,’ Hengguan 35 ’(semi-winter)was used as the test material,and field warming experiments were conducted in a simple polyethylene steel greenhouse after vernalization of winter wheat in two consecutive growing seasons from 2020 to 2022.In the growing season of 2020-2021,five warming treatments were set up:the starting date of warming was January 25(WT1),February 1(WT2),February 8(WT3),February 15(WT4)and February 22(WT5),respectively,and the end date of warming was March 15.In order to test the effects of different warming starting and ending dates and longer warming duration on wheat growth and development between years.In the 2021-2022 growing season,five warming treatments were also set up:the starting date of warming was January 25,and the ending date of warming was April 5(WT1),March 28(WT2),March 20(WT3),March 12(WT4)and March 4(WT5).Nonventilation treatment(HT)was set up,and the start and end dates of warming treatment were consistent with WT1.The purpose of this study was to explore the effects of staged warming in late winter and early spring on the physiological mechanism of panicle development,grain number formation,grain yield formation and quality of winter wheat,and to provide theoretical basis for the exploration of yield potential and quality improvement of winter wheat in North China Plain.The main research results show that:1.Moderate warming during late winter and early spring advances the greening and spike differentiation period of winter wheat,resulting in exposure to relatively low temperature during various growth stages after jointing.This effectively prolongs the effective growth period and spike differentiation period after greening,significantly increasing the length of young spikes and providing favorable conditions for the growth of wheat plants,spike development and grain filling.2.Moderate warming during late winter and early spring significantly increases the plant height and photosynthetic area of winter wheat.Although warming treatment reduces the photosynthetic capacity of flag leaf in the booting stage due to exposure to low temperature after membrane peeling,the significant increase in photosynthetic area raises the total net photosynthesis rate of flag leaves by 8.6%-32.2%,promoting the accumulation of assimilates in wheat.In the 2021-2022 growing season,warming treatment significantly increases the content of indole-3-acetic acid(IAA)and gibberellins(GA3),while decreases the content of abscisic acid(ABA)in both flag leaf and spike,promoting the development of young spikes and differentiation of small flowers.This is beneficial to the synthesis and accumulation of water-soluble carbohydrates,significantly increasing the content of sucrose and soluble sugar in various organs of wheat plants and promoting assimilate accumulation in spike,which in turn increases the dry matter accumulation of spike by 3.9%-41.3%.Meanwhile,moderate warming during late winter and early spring improves the spike morphology of wheat and significantly increases the number of grains per spike by 7.4%23.7%.3.Moderate warming during late winter and early spring increases the effective number of spikes in winter wheat,but if the duration of warming continues for too long,it causes premature polar differentiation of tillers,resulting in reduced effective spike numbers and limiting the promoting effect of warming on yield.Moderate warming during late winter and early spring significantly increases the biomass production of winter wheat,improves the dry matter transfer before anthesis,increases the contribution rate of grains,and raises the average grain filling rate,resulting in an increase in grain weight by 0.8 g-4.9 g compared with CK,and a yield increase of 4.9%-28.3%.Moderate warming during late winter and early spring reduces the grain protein content,wet gluten content and sedimentation value of wheat,but increases the protein yield per unit area and grain starch content.4.The no-ventilation treatment(HT)during late winter and early spring leads to high temperatures(daily maximum temperature during warming treatment>30℃,with the highest temperature reaching 43.9℃),which have a significant negative impact on the development of young spikes,photosynthetic assimilation and accumulation,spike number,grain number,yield,grain protein yield,and grain starch content of winter wheat.However,it has a promoting effect on the grain protein content.To sum up,moderate warming during late winter and early spring can cause winter wheat to break dormancy earlier and prolong spike differentiation and grain filling time.This can increase the net photosynthesis capacity of flag leaves,increase the content of IAA and GA3 in flag leaves and young spikes,promote the accumulation of sucrose and soluble sugars,provide sufficient assimilates for increasing grain number and weight,and significantly increase yield.However,if the duration of moderate warming during late winter and early spring is too long,this will reduce the effective number of spikes and limit the potential increase in wheat yield.Therefore,under the current climate conditions,the highest grain and protein yields can be achieved by warming from January 25th to March 15-20th(a warming duration of 50-56 days and a cumulative temperature increase of 156.1-181.2℃).