Effects Of Warming Adaptation On Ear And Carbon And Nitrogen Metabolism Characteristics Of Wheat Under High Temperature Stress

At present,global warming is the main trend of climate change.Global warming presents the characteristics of asymmetric warming,which the increase in daytime is lower than night,and the increase in summer and autumn is lower than winter and spring.At the same time,extreme weather led to an increase in the number of hot days in a year,and heat stress seriously affected the growth of wheat.Based on this,night warming and high temperature treatment were carried out on wheat during 2021-2022.Taking Yangmai 18（spring variety）and Yannong 19（semi-winter variety）as experimental materials,passive night warming was carried out on wheat at various growth stages,i.e.,tiller stage to jointing stage(W_T-JN),jointing stage--booting stage(W_J-BN),booting stage--flowering stage(W_B-AN),and wheat were treated with high temperature stress at filling stage,to explore the effects of warming adaptation at night on the characteristics of wheat ear and carbon and nitrogen metabolism under high temperature stress at filling stage.The results show that:1.Night warming adaptation accelerated the differentiation of young ears and the number of pregnant spikelets,which was beneficial to the increase of yield.Under the conditions of W_T-JN and W_J-BN,the tillering stage shortened the vegetative growth stage of seeding and flowering,and prolonged the filling stage.The increase of total spikelets,pregnant spikelets and 1000-grain weight was beneficial to the formation of yield.Early night warming adaptation alleviated wheat yield loss under high temperature stress at filling stage.Compared with the control,the yield of the night warming treatment increased by 3.08%to7.62%compared with the control,while that of the high temperature stress treatment increased by 1.21%to 6.05%.2.Night warming adaptation improved the photosynthetic respiration of wheat at night,enhanced the photosynthetic capacity of wheat during the day and alleviated the weakening of photosynthetic capacity of wheat flag leaves under high temperature stress at filling stage.High temperature stress reduced the photosynthetic capacity of wheat flag leaves mainly by reducing net photosynthetic rate,intercellular CO₂ concentration,stomatal conductance and transpiration rate.The decrease of photosynthetic capacity is not conducive to improving the generation and transport of photosynthates,which reduces the accumulation and distribution of dry matter,and ultimately leads to the decrease of yield.3.Night warming adaptation was beneficial to nitrogen accumulation and utilization by increasing the activity of nitrogen assimilation enzyme.W_T-JN and W_J-BN increased the contents of free amino acid and soluble protein in flag leaves at filling stage,and promoted the accumulation of nitrogen in the above-ground part of wheat by increasing the activities of NR and GS enzymes.The decrease of nitrogen accumulation under high temperature stress at filling stage was alleviated after tillering stage to jointing stage and jointing stage to booting stage.4.After W_T-JN treatment,a large number of differential genes were enriched during oxygen biosynthesis and photosynthesis in wheat.Through the GO enrichment and KEGG pathway analysis,we finally identified 14 differentially related genes related to nighttime warming,and the expression of differentially related genes in related pathways responds to leaf temperature adaptability.In conclusion,night warming adaptation can improve the photosynthetic capacity and material production capacity of wheat,and coordinate the balance of plant carbon and nitrogen metabolism.Thus are beneficial to alleviate the loss of wheat grain yield under high temperature stress during filling stage.The results of this study will provide theoretical support for wheat cultivation under the background of climate warming in the future.