| Drought is the main abiotic stress that affects the growth and development,yield and quality of wheat.In the winter wheat planting area of Huang-Huai-Hai,droughts frequently occur during grain filling stage,and the senescence process of wheat plants is accelerated,which seriously affects the synthesis and transportation of photosynthetic compounds in the functional leaves of wheat,and reduced the yield and quality of wheat.Different wheat varieties have significant differences in response to water deficit due to their different genetic backgrounds,and therefore have different performances in wheat functional leaf physiological and biochemical characteristics and yield components.Therefore,this experiment studied the differences in flag leaf physiological and biochemical characteristics,protein expression and yield components of wheat varieties with different water sensitivity levels under water deficit treatments.It is expected to provide a theoretical basis for the selection of wheat drought-resistant and stable product varieties and the optimization of cultivation control measures.The experiment was carried out in the canopy of the experimental station of Shandong Agricultural University in the two wheat growing seasons from 2019 to 2021.The experiment adopted a split-splitting area test design,the main area was two wheat varieties,and the drought-resistant variety Shannong 16(SN16)and the water sensitive variety Shannong 22(SN22)were selected as the test materials.Four water gradients were set up in the secondary area,and the water was controlled during grain filling stage.The water gradients are normal irrigation(WW,0-20 cm soil relative water content is set to 75%-80%),and mild water deficit(Mi WD,0-20 cm soil relative water content is set to 65%-75%),moderate water deficit(Mo WD,0-20 cm soil relative water content is set to 50%-60%),severe water deficit(SWD,0-20 cm,the relative soil moisture content is set to 30%-40%).The main findings are as follows:1.The effect of water deficit on yield,grain weight and dry matter accumulation and distribution of wheat during grain filling stageWater deficit during grain filling stage significantly reduced the yield of wheat,and with the increase of water deficit in grain filling stage,the yield of two wheat varieties increased.The grain weight of two wheat varieties decreased significantly with the increase of water deficit,SN16 decreased by 4.81%-15.31%,SN22 decreased by 6.22%-16.46%.Finally,the output of SN16 decreased by 1.26%-9.38%,and the output of SN22 decreased by3.27%-14.37%.The decrease of SN22’s grain weight under SWD treatment was higher than that of SN16,indicating that severe water deficit has a higher impact on SN22 yield,which is mainly reflected in the increase of grain weight decrease caused by water deficit.In addition,with the increase of water deficit,the plant dry matter weight of SN22 was significantly lower than that of SN16,and the plant dry matter weight of SN22 was significantly lower than that of SN16.2.The effect of water deficit during grain filling stage on the ratio of green leaf area of wheat flag leaves and the interception rate of canopy light energyWater deficit during grain filling stage has a significant impact on the green leaf area ratio of wheat flag leaves and the interception of canopy light energy.The results showed that with the extension of the water deficit time and the intensification of the stress,the ratio of the green leaf area of the flag leaves of the two varieties of wheat showed a downward trend,and the leaf function period was shortened;Both the light interception amount and the light energy interception rate in the upper canopy showed a decreasing trend,which was not conducive to the light energy utilization and material production of the wheat canopy.SN22 is more sensitive to water deficit than SN16.The senescence in the upper canopy of SN22 is earlier than that of SN16.Its flag leaf green leaf area ratio,light interception in the upper canopy and light energy interception rate are all lower than SN16.3.The effect of water deficit during grain filling stage on the physiological and biochemical characteristics of wheat flag leavesThe contents of chlorophyll,carotenoids,malondialdehyde(MDA)and antioxidant enzyme activities in flag leaves of two wheat varieties under different water deficit treatments were analyzed.The results showed that the chlorophyll content and antioxidant capacity of wheat flag leaves decreased with the increase of water deficit,and the MDA content increased with the increase of water deficit.It showed that the degree of damage to the cell membrane system of wheat flag leaf was SWD>Mo WD>Mi WD>WW.In addition,the water-sensitive variety SN22 has higher MDA content than the drought-resistant variety SN16,and has lower superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities.Therefore,under water deficit conditions,the water-sensitive cultivar SN22 flag leaves have weak antioxidant capacity,and it was difficult for wheat to maintain the balance of active oxygen in the body,and it was more susceptible to photosynthetic damage and oxidative stress.4.The effect of water deficit during grain filling stage on the expression of wheat flag leaf proteinIn order to clarify the response mechanism of wheat to water deficit during grain filling stage at the protein level,the proteomic analysis of wheat flag leaves on the 10 th day of water deficit treatment was carried out to screen different proteins,and perform functional analysis,protein localization and cluster analysis of differential proteins.The results showed that the concentration of total protein in flag leaves of two wheat cultivars under severe water deficit was lower than that under moderate,mild water deficit and normal water deficit.Compared with WW treatment,water deficit treatments(Mi WD,Mo WD,SWD)induced a total of 409 differential proteins.The abundance of differentially expressed protein showed that with the increase of water deficit during grain filling stage,SN16 first decreased and then increased,while SN22 increased.Under mild water deficit,the differential protein abundance of SN16 was higher than SN22,but under moderate and severe water deficit,the differential protein abundance of SN16 was lower than SN22.In addition,the differentially expressed proteins were mainly located in the chloroplast,nucleus and cytoplasm,and the most differentially expressed proteins were located in the chloroplast.Through KEGG enrichment analysis,the results show that the differential proteins were mainly divided into four categories.The first category is related proteins such as antioxidant and stress resistance,which are mainly enriched in the interaction of plant pathogens,phenylacetone biosynthesis,phagosomes,tyrosine metabolism and other pathways;The second category is lipid and energy metabolism-related proteins,which are mainly enriched in glycerolipid metabolism,glycerophospholipid metabolism,oxidative phosphorylation and other pathways;The third category is protein synthesis pathway related proteins,which are mainly enriched in ribosomes,spliceosomes,endoplasmic reticulum protein processing,RNA transport and other pathways;The fourth category is photosynthesis-related proteins,which are mainly enriched in photosynthesis and photosynthesis-antenna protein pathways.Compared with WW treatment,RNA transport,phytopathogen interaction,spliceosome and other related proteins were all up-regulated under SWD treatment of the two varieties,while the photosynthetic pathway-related proteins were all down-regulated.It is inferred that after water deficit treatment,a series of stress resistance reactions occur in the wheat body,the biosynthesis of flag leaf protein was affected,the peripheral antenna system in the chloroplast is destroyed,the light energy absorption process was difficult to proceed normally,photosynthesis was inhibited,and the photosynthetic efficiency was reduced.The process of energy exchange and material production in wheat was affected.In addition,under SWD treatment,the expression of SN22 proteins involved in glycerolipid metabolism was up-regulated.This result may be related to the destruction of the lipid bilayer of the cell membrane of wheat flag leaves,cell defense and increased plant energy metabolism under water deficit stress. |
