Effects Of Short And Medium Chain Fatty Acids (SMCFAs) On Growth,Drought Resistance And Fruit Quality Of Peach Tree

In recent years,peach industry has gradually entered the global economic market,with the expansion of peach planting area and the increase of labor costs,a variety of biological stimulants came into being.Fatty acids are an important group of physiological chemicals that play a role in energy conversion,membrane structure and many signaling pathways in cells.A growing body of research shows that the use of biostimulants or fatty acids to enhance plant growth is a successful and environmentally beneficial strategy.In this paper,the effects of six Short medium chain fatty acids（SMCFAs）on the growth,physiology,biochemistry,and fruit quality of peach trees were investigated through field and laboratory experiments.At the same time,the physiological and molecular mechanisms of lauric acid adaptation to drought stress were investigated by using transcriptomic and metabolome techniques.And the effects of Lauric acid（LA）on soil microorganisms,so as to take practical technical measures for the production of short and medium chain fatty acids,in order to provide a theoretical basis for further understanding of the lauric acid-mediated drought response mechanism of peach.The main research results are as follows:（1）Among the low concentration of short and medium chain fatty acids,acetic acid,butyric acid,propionic acid,nonaic acid,capric acid and lauric acid had effects on the growth of peach trees.The best comprehensive effects were butyric acid and lauric acid,and exogenous addition of lauric acid and butyric acid could effectively improve the root vitality of peach seedlings,which was increased by 26.48%and 19.79%compared with CK.Lauric acid and butyric acid had the best effect on SPAD and photosynthesis,which increased by13.6%,14.61%and 27.81%,25.70%,respectively.For water utilization,lauric acid and butyric acid had the most obvious effect,which increased by 20.75%and 16.53%compared with CK.（2）In the study of the effect of acetic acid,butyric acid,propionic acid,nonaic acid,capric acid and lauric acid on peach fruit quality,butyric acid and lauric acid can effectively increase single fruit weight by 64.35%and 69.7%,respectively.Compared with CK,soluble solids were increased by 11.57%and 17.27%,respectively,and could improve the content of sugar components（sucrose,fructose,glucose,sorbitol）in fruit,and the generation of esters in fruit aroma,while acetic acid had no effect on fruit quality.（3）LA can effectively alleviate the effects of drought stress on peach trees.In addition to regulating leaf photosynthetic capacity and pore characteristics,its mechanism of action can also regulate related enzyme activity to maintain high leaf water content,photosynthesis,antioxidant capacity,osmoregulatory substances and relative growth rate,which improves the tolerance of drought stress.Through transcriptomic analysis,it was found that exogenous LA treatment can regulate the differential gene response of peach to drought stress,which mainly involves plant-pathogen interaction,Sesquiterpenoid and triterpenoid biosynthesis,MAPK signaling pathway,Phenylpropanoid biosynthesis,Cyanoamino acid metabolism,and Cutin,suberine and wax biosynthesis,thereby enhancing the drought resistance of peach.LA pretreatment affected the transcription levels of related genes in the auxin（AUX）,salicylic acid（JA）,and abscisic acid（ABA）signal transduction pathways and Ca²⁺pathway signals under drought stress,suggesting that LA may interact with a variety of hormones to regulate the drought adaptation of peach seedlings.（4）Extensive targeted metabolomics was used to identify the metabolites of peach leaves treated with lauric acid under drought stress.A total of 1,431 compounds were identified.In the LA-D vs CK-D comparison group,31 metabolites were up-regulated and 226 metabolites were down-regulated.The metabolic pathways annotated by the results:ascorbic acid and aldehyde acid metabolism,inositol phosphate metabolism,carbon metabolism,isoflavone biosynthesis,phosphonate and hypophosphonate metabolism,etc.,mainly involved in drought regulation of metabolic substances such as quercetin,rutin,sugars,amino acids and their derivatives.Combined metabolomics and transcriptomics To analyze the effects of exogenous lauric acid on peach seedlings under drought stress,it is possible to use carbon metabolism to maintain cell homeostasis under drought stress,and at the same time through ascorbic acid and aldehyde acid metabolism,inositol phosphate metabolism,glyceride metabolism,glycerophospholipid metabolism,fructose and mannose metabolism,carbon fixation in photosynthetic organisms,etc.,to maintain redox balance,regulate osmotic pressure,and reduce the damage of drought stress.（5）Under drought stress,lauric acid treatment of peach-root soil had certain effects on the relative abundance of dominant bacterial groups in soil,and increased the relative abundance of nitrohydroomonas,RB41,Nitrococcus and Acinetobacter,and also affected the relative abundance of horizontal functional bacteria in other genera.