Effects Of Exogenous ABA On The Radiation Utilization And Photoassimilates Transportation In Wheat Under Drought Stress During Post Anthesis

The Huang-Huai-Hai area is the main producing area of wheat in China.The rainfall season was unevenly distributed.The average annual rainfall during the growing season of wheat accounted for only 35%-50%of the water requirement during the whole growth period.Therefore,this experiment studied the regulation of exogenous ABA on the radiation and photoassimilates transportation wheat under drought stress.The effects of exogenous ABA on canopy temperature and assimilates accumulation and distribution of different genotypes of wheat under drought conditions was investigated.Aiming to supply theoretical basis for improving the stress resistance of stable yield and the weight gain after anthesis.The experiment was carried out in the shelter pool of the experimental farm of Shandong Agricultural University in Shandong Tai'an,Shandong Province from 2016-2018.The water sensitive variety Fu 287?F287?and the drought-tolerant variety Shannong 20?SN20?were selected in this experiment.The experiment was conduct with two water gradients,normal irrigation conditions?75%-80%of the field moisture capacity,expressed in W?and water stress conditions?40%-50%of the field moisture capacity,indicated by D?.The experiment also set up exogenous hormone treatment.At the beginning of the flowering period,10 mg·L^-1exogenous ABA?American Sigma?was sprayed at a rate of 100 mL·m^-2 for 4 days after anthesis?DAA?.The water containing 0.5%?V/V?Tween-20 was sprayed as a control?CK?.The main results were as follows:1.The effects of exogenous ABA on canopy temperature of wheat under drought conditionsAfter drought treatment,the leaf and spike temperature of the two varieties was significantly increased,resulting in a significant decrease in canopy temperature depression?CTD?and a significant increase in the spike-leaf temperature depression?SLTD?.During the whole grain filling stage,the leaf temperature of SN20 was significantly higher than that of F287,and the spike temperature was significantly lower than that of F287.The CTD and SLTD of SN20 in the middle and late filling stage were significantly lower than those of F287.It indicated that the heat dissipation of leaves of drought-tolerant varieties was lower than that of water-sensitive varieties.Spraying exogenous ABA could significantly increase the leaf temperature of the two varieties and significantly reduce the spike temperature,CTD and SLTD.The interaction between cultivars and ABA had significant effects on SLTD,and the interaction between water conditions and ABA had significant effects on CTD and SLTD.2.The effects of exogenous ABA on photosynthetic mechanism activity of wheat under drought conditionThe PI_abs?the photosynthetic performance index?and?₀?the probability that a trapped exaction transfers an electron into the electron transport chain beyond Q_A^-?of the two varieties were significantly reduced under drought condition,especially in the late filling stage,both of which decreased by 50%the above.The PI_abs and?₀ value of SN20 were higher than that of F287 during the filling stage.It showed that drought-tolerant varieties have stronger ability to absorb light energy and transmit electrons than water-sensitive varieties.Spraying ABA could significantly increase the PI_abs and the?₀ value.It showed that spraying ABA can improve the activity of photosynthetic mechanism,thus providing more light energy and assimilation force for optical contracting.The relative expression levels of psbA genes in both varieties were significantly reduced under drought treatment.During the whole grain filling stage,the relative expression of psbA gene in SN20 under drought treatment was significantly higher than that in F287.This indicated that drought-tolerant varieties were less affected by water stress than water-sensitive varieties,and could maintain normal psbA gene expression levels to synthesize more D1 proteins to maintain their photosystem activity.Exogenous ABA significantly reduced the relative expression of psbA gene.Compared with DCK treatment,the relative expression levels of psbA gene in F287 and SN20 increased by56.64%and 29.29%,respectively.3.The effects of exogenous ABA on the photosynthetic assimilative power of wheat under drought conditionsAfter drought treatment,the net photosynthetic rate?P_N?,stomatal conductance?g_s?and transpiration rate?T_r?of the two varieties decreased significantly,and the decrease was larger in the middle and late stages.The carboxylation efficiency?CE?of both varieties after anthesis increased and then decreased,reaching a maximum at 21 DAA.The leaf water use efficiency?WUE_L?of F287 under the drought treatment was significantly lower than that of the normal irrigation treatment.On the contrary,the WUE_L of SN20 under the drought treatment showed a slight increase trend.the CE of flag leaf of drought-tolerant varieties in the middle and late filling stage is relatively stable.Spraying ABA significantly increased WUE_L,P_N,CE and significantly reduced g_s,T_r.At 21 DAA,Compared with DCK treatment,the P_N of exogenous ABA treatment under F287 and SN20 increased by 53.35%and 31.31%,and g_s decreased by 35.46%and 47.74%,and T_r decreased by 19.34%and 32.23%,respectively.It is indicated that exogenous ABA could enhance the water retention capacity of leaves by reducing the leaves g_s and T_r,so as to improve the photosynthetic capacity of flag leaves and prolong the photosynthetic duration.4.The effects of exogenous ABA on grain filling of wheat varieties under drought conditionDrought treatment significantly reduced the strong and weak grain weight of the two varieties,and the reduction was greater in the middle and late stages.Compared with WCK treatment,the maximum grain filling rate,average grain filling rate and active growth stage of F287 were significantly reduced,and the maximum grain filling rate and average grain filling rate of SN20 were significantly reduced.It indicated that the water-sensitive varieties reduced the grain weight by reducing the grain filling rate and shortening the active growth stage under drought condition.The drought-tolerant varieties mainly reduced the grain weight by reducing the grain filling rate.Compared with DCK treatment,the maximum grain filling rate,average grain filling rate,active growth stage and actual grain filling stage of the two varieties were increased after exogenous ABA treatment.It indicated that the increase of grain weight after ABA treatment was mainly due to its ability to promote grain filling,increase the filling rate and prolong the active growth stage.5.The effects of exogenous ABA on dry matter accumulation and distribution and yield of wheat varieties under drought stressThe total weight and grain weight of the two varieties were significantly reduced under drought condition.Compared with WCK treatment,the dry matter translocation and post-anthesis storage capacity of the two varieties after the DCK treatment significantly decreased the contribution rate to the grain,and the moisture sensitive variety decreased more than the drought-tolerant variety.Compared with DCK treatment,DABA treatment significantly increased the contribution of post-anthesis dry matter transport and post-anthesis assimilate transport to grain.It indicated that the dry matter in the drought-tolerant varietiy mainly originated from the dry matter accumulation after anthesis,and the water-sensitive varietiy dry matter was derived from the transport of the pre-flowering storage assimilates of the vegetative organs and the accumulation of dry matter after anthesis.The yields of the two cultivars were significantly lower than that of normal irrigation under drought treatment.The water-sensitive cultivars F287 had a higher yield than the drought-tolerant variety SN20.Spraying ABA could alleviate the reduction of drought to1000-grain weight.In a word,significant effects on grain weight and yield were obtained from interaction treatment between exogenous ABA and variety,water condition?P<0.01?.Interaction between Variety and water conditon and interaction between water condition and ABA had significant effects on grain weight and yield?P<0.05?.