Regulatory of Exogenous Melatonin on Floret Development and Carbon Nutrient Metabolism in Winter Wheat Under Drought Stress
[Objective]This study aimed to clarify the regulatory effects of exogenous melatonin on floret development and carbon nutrient metabolism in winter wheat under drought stress.[Method]Two soil water conditions (drought stress treatment:D,and normal moisture treatment:W) were set up using multi-spike variety Yumai 49-198 and large-spike variety Zhoumai 22 as experimental wheat materials,with foliar spraying 100 μmol·L-1 exogenous melatonin (MT) and clear water control (CK) before the peak of floret degradation (about 20 days after jointing) in 2021-2023,focusing on the effects of exogenous melatonin on the number and morphological characteristics of floret development,SPAD value,net photosynthetic rate,sucrose content and its metabolic enzyme activities of top spread leaves,and yield component factors of winter wheat under drought stress.[Result]The drought stress led to an increase in floret degradation and abortion in wheat,while spraying exogenous melatonin could effectively reduce floret degradation and abortion,and increase number of fertile florets of the two varieties,but could not completely counteract the negative effect of drought stress;exogenous melatonin also showed positive regulatory effect on normal water treatments of the two varieties.Spraying exogenous melatonin could effectively increase SPAD value,net photosynthetic rate,carbon metabolism-related enzyme activities of top spread leaves and spike sucrose content of the two varieties under drought stress and normal water treatment,and the increase range was higher in drought treatment than in normal water treatment;exogenous melatonin decreased sucrose content of stem and leaf organs of both varieties under drought stress,but the opposite was true under normal water treatment.Spraying exogenous melatonin significantly increased grain number per spike of two varieties under two moisture treatments,compared with no-spraying MT treatment,the grain number per spike of Yumai 49-198 with spraying MT treatment increased by 19.12％ (D) and 6.65％ (W),respectively;the grain number per spike of Zhoumai 22 with spraying MT treatment increased by 21.57％ (D) and 8.73％ (W),respectively;spraying MT showed some regulation effect on spike number and thousand grain weight of the two varieties under the same water treatment,but did not reach a significant level.Compared the differences between two varieties,the regulatory effect of spraying melatonin was overall higher in the large-spike variety Zhoumai 22 than in the multiple-spike variety Yumai 49-198.[Conclusion]Spraying exogenous melatonin before the peak of floret degradation could effectively increase the SPAD value,net photosynthetic rate,and carbon metabolism-related enzyme activities of top spread leaves in wheat,and promote synthesis of photosynthesis products and the distribution and transportation of sucrose from stem and leaf nutrient organs to spike organ,which could provide sufficient nutrient security for the development of florets to increase number of fertile florets,thereby increasing grain number per spike,and the regulating effect on the large-spike variety of Zhoumai 22 was more pronounced.The results of this study provided the theoretical basis and technical support for increasing grain number per spike,stabilizing yield and reducing disaster under drought stress through the application of exogenous melatonin.
winter wheatdrought stressmelatoninfloret developmentgrain number per spikecarbon metabolism
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