Analyses On Primary Drives Of Stomatal Movement And Genotypic Differences In Stoma And Metabolism Responses For Winter Wheat Under Different Water Conditions

As the increasing serious global water resource crisis,water shortage has become one of the important factors restricting plant growth and crop production.Stomata is the channel for water and gas exchange between plants and the outside environment,and is closely related to the two plant physiological functions,photosynthesis and transpiration.Deeply understanding the stomatal characteristics differences among winter wheat genotypes,analyzing the main driving force of stomatal movement and revealing the metabolic characteristics of stomata in response to severe drought stress can provide scientific guidance for breeding of water-saving genotypes,development of cultivation water-saving technology and genetic improvement of water-saving traits of genotypes.In this paper,15 winter wheat genotypes were selected as experimental materials to study the diurnal variation pattern of stomatal conductance(Gs)under different soil water conditions and atmospheric relative humidity,the response of Gs to meteorological factors and its relationship with transpiration and photosynthesis;reveal the physiological phenomenon of photosynthesis involved in stomatal regulation by affecting intercellular carbon dioxide concentration(Ci)and explores the main driving force of stomatal movement;high-throughput testing and analysis methods such as metabolomics are used to study the characteristic metabolites of stomatal response to severe drought stress.The main conclusions are as follows:(1)It was found that the genotypes and atmospheric humidity were the key determinants of the Gs diurnal variation pattern by studying the Gs diurnal variation pattern in the 15 wheat genotypes under different soil water conditions and different atmospheric relative humidity.Under moderate relative humidity(MRH),all genotypes showed a single-peak curve pattern,but their Gs peaked at different time,with a difference of about 2 h.At low relative humidity(LRH)and high relative humidity(HRH),most genotypes showed a gradual decline pattern from morning to afternoon.Therefore only when the Gs diurnal variation pattern and peak value are consistent,the genotypes with significant differences in Gs can be selected,this result is of great significance for the identification and selection of winter wheat genotypes.(2)The diurnal variation of six wheat genotypes under different soil moisture conditions and different atmospheric humidity conditions was explored to study the relationship between Gs and meteorological factors.It is found that the relationship between Gs and atmospheric factors in the process of diurnal variation depends on the moisture condition through the path analysis of the four meteorological factors,temperature,atmospheric relative humidity,water vapor pressure deficit and photosynthetically active radiation.The correlations between the four factors and Gs were much higher under HRH than those under LRH and MRH.When RH was at the same level,the correlations between Gs and the four factors were mostly higher under WW than those under DS.It is found that Gs and Pn show extremely significant correlation in the process of diurnal variation under different humidity conditions through the analysis of the correlation between Gs and photosynthetic rate(Pn)and transpiration rate(Tr)in the process of diurnal variation of six genotypes,while the correlation between Gs and Tr is extremely significant only at low and medium humidity,but there is no correlation between them at high humidity.(3)Pn and Gs increased gradually with PAR and increased synchronously with the same trend under the constant Ca condition;Gs showed a basically unchanged trend with the constant Ci under the constant Ci condition of;Under the conflicting conditions of the induced stomatal movement opposite direction,the direction of stomatal movement coincides with the direction induced by Ca.Plants treated with NF caused chlorophyll peroxidation and produce albinized leaves,and it was found that the photosynthesis of green leaves could induce the opening of stomata in albino leaves by affecting the change of Ci.Pn decreased gradually with time,Gs decreased and Ci maintained a high level all the time after the leaves were treated by DCMU that inhibit PSII photosynthetic electron transport and AOA that inhibit rubisco,the key enzyme in the carbon fixation process in photosynthesis.The ABA treatment experiment found that ABA treatment had no effect on photosynthesis,so it did not affect Ci but directly induced the decrease of Gs,which was an independent way to induce the decrease of Gs.The drought stress treatment experiment found that with the prolongation of drought stress time,the degree of drought gradually increased and after entering the non-stomatal-limited stage,Ci gradually increased.Gs increased after artificially reducing Ca to decrease Ci,indicating that increased Ci was involved in the regulation of stomatal movement under severe stress which caused photosynthesis to enter a non-stomatal-limited stage.(4)Jinmai 47 and 908216(type I genotypes)with lower Gs and Pn under severe drought stress had lower biomass accumulation during the stress period,but higher final grain yield;Lankaoaizao 8 and Zhengmai 9023(type II genotypes)with higher Gs and Pn under severe drought stress had higher biomass accumulation during stress,but lower final grain yield.The high-throughput targeted metabolomics was used to analyze the metabolic characteristics of two types of winter wheat genotypes with different stomatal characteristics under drought stress.The results showed that proline was significantly increased,glutamic acid which is proline synthesis precursor was also significantly increased;trans-citric acid and malic acid were also significantly increased in type II genotypes,which was helpful for that type II genotypes enhanced the ability of cell osmotic regulation,kept stomata open and maintained photosynthesis under severe drought stress.In type I genotypes,phenylalanine and some phenolic acid metabolites(ferulic acid,salicylic acid,syringaldehyde,4-Methoxycinna Maldehyde and caffeic acid))related to lignin synthesis increased significantly,which contributed to alleviating root damage and strengthened the protection function of cells under severe drought stress.