Effects Of Exogenous Melatonin On Growth Of Wheat Seedlings Under Salt Stress

Wheat is one of the three major grains in the world,rich in nutrients,and is the most widely distributed and most cultivated crop in the world.Soil salinization endangers wheat growth,so it is crucial to improve the normal growth of wheat in saline soil.Melatonin(Nacetyl-5-methoxy,Melatonin,MT,chemical formula C13H16N2O2)and auxin structure is similar,is a kind of compounds,widely exists in plants,animals and plants,its has important regulating plant physiological activities,such as seed germination,growth,rooting,photosynthesis and give plants the ability to resist bad environment,and alleviate low temperature,salt ion adversity damage to plants.However,the relationship and mechanism of how melatonin affects the growth and development of wheat seedlings under salt stress are still unclear.In this study,the paper used Yangwheat 13 as the test material,and used the methods of resin section,physiological and biochemical determination and transcriptome sequencing to study the effect of melatonin on the growth and development of wheat seedlings under salt stress.The main study results are presented as follows:(1)Salt stress significantly affected the biomass and root crown ratio of wheat seedlings,and also inhibited the root growth and root vitality of wheat seedlings,while exogenous spraying of MT at different concentrations could effectively alleviate the inhibition of salt stress on wheat seedlings,and the best effect was at the melatonin concentration of 200 μmol/L.(2)Under salt stress,the soluble sugar of wheat seedlings decreased significantly,while the content of malondialdehyde and proline increased significantly,the leaf cell membrane was significantly damaged,the cells produced a lot of reactive oxygen species caused oxidative stress,and the protective enzyme activity was reduced.Exogenous melatonin can effectively alleviate the degree of cell membrane damage and increase the protective enzyme activity of wheat seedlings under salt stress,and significantly improve the tolerance of wheat seedlings to salt stress.(3)Leaf chlorophyll content decreased significantly,maximum photochemical efficiency Fv/Fm decreased,photochemical quenching coefficient Qp decreased,nonphotochemical quenching coefficient NPQ increased,and leaves consumed excessive energy by improving heat dissipation.Exogenous melatonin can significantly alleviate the effects of salt stress on chlorophyll and fluorescence parameters,improve the electron transport efficiency,protect the photosynthetic structure,and improve the photosynthetic efficiency,thus alleviating the salt stress damage.(4)By sectioning,mesophyll cells wrinkled,the number of chloroplasts decreased,vesicle of thylakoids,and wrinkled cells of root epidermis and cortex in wheat seedlings under salt treatment.Exogenous melatonin treatment can effectively alleviate the destruction of mesophyll cell,chloroplast and root structure.(5)Transcriptome sequencing showed that the intersection of differential genes with salt and 200 μmol/L MT treated groups was screened to 89 common genes.In the KEGG pathway enrichment analysis of differential genes,four pathways were co-enriched,and 13 metabolic pathways were closely associated with wheat protection against salt stress.The above results show that salt stress has affected the morphological structure and physiology of wheat seedlings,and a certain concentration of melatonin can effectively alleviate the inhibitory effect of salt stress.The results can not only deepen the study of salt tolerance mechanism of wheat seedlings,but also provide a theoretical basis for melatonin to enhance salt tolerance and quality improvement of wheat seedlings.