The Mechanism And Regulation Of Glycerol-3-Phosphate In Organic Fertilizer Improve P Nutration And Salt Stress Resistance Of Watermelon

Excess application of chemical fertilizers caused some problems such as resources wasting and environmental pollution.Substitution of chemical fertilizer with organic fertilizer is efficient fertilization and keeping sustainable agriculture.Organic fertilizer has special functions on improving crop yield,quality,as well as alleviating stress with multiple nutrients.Organic fertilizers provide abundant phosphorus nutrient for crops as organic phosphorus.Some of which are small molecule,organic phosphorus.Glycerol-3-phosphate（G3P）is an important organic phosphorus in organic fertilizers with about 3%-5%of organic phosphorus.Glycerol-3-phosphate in plant take actions in resistance to abiotic stress.However,the contribution and mechanism of glycerol-3-phosphate in organic fertilizer on phosphorus nutrition and the roles of resistance to salt stress is not clear.This study demonstrated that glycerol-3-phosphate in organic fertilizer was transported to root by glycerol-3-phosphate transporter in watermelon,thereby regulating G3P synthesis and metabolism related enzymes and crop utilization of phosphorus nutrition;This study also confirmed that organic G3P in fertilizer nutrition improved watermelon resistance to salt stress.Furthermore,adding G3P to organic fertilizer enhanced salt stress resistance of watermelon.This study provides theoretical evidence and technological method for organic fertilizer alleviating salt stress of watermelon.The main findings are as follows:1.The ³¹P-NMR nuclear magnetic resonance spectrometer was used to determine the content of G3P in organic manure in cow manure and pig manure.The results showed that the G3P content in dairy manure and swine manure were 0.04 g·kg^-1 and 0.01 g·kg^-1,respectively,which is 0.33%and 0.21%of total phosphorus,respectively.2.The hydroponic experiment was used to study the response of G3PT expression and G3P concentration in watermelon to G3P or organic fertilizer application.The results showed that the expression of the gene Cla G3PT1 was significantly upregulated by phosphorus deficiency.The expression of the gene Cla G3PT2 in the leaves and roots treated with 25%OF and G3P was significantly higher than that in chemical fertilizer nutrition.The results showed that the G3P concentration in watermelon responded to the G3P and organic fertilizer supply.The concentration of G3P in roots,xylem sap,and leaves was positively correlated with the concentration of G3P supplied by roots.3.Hydroponic experiments were carried to demonstrated that G3P and organic fertilizer nutrition promoted the transportation of inorganic phosphorus from roots to above ground.There was no difference in inorganic phosphorus and total phosphorus content in root slices and stems of watermelon under 25%treatment,while the content in leaves increased significantly.Under G3P treatment,the content of inorganic phosphorus in the roots of watermelon was significantly reduced,but there was no difference in the content of total phosphorus,the content of inorganic phosphorus and total phosphorus in the stems,and the content of inorganic phosphorus and total phosphorus in the leaves increased.4.Hydroponic experiment was carried out to study the response of glycerol-3-phosphate synthesis and metabolism related enzymes to organic fertilizer nutrition and G3P.The results showed that the expression of the gene Cla GPDH3 in the roots of watermelon under the treatment of 0.25 m M G3P was significantly lower than that of the chemical fertilizer treatment,while the expression of the gene Cla GPDH3 in the roots of the 25%OF treatment was reduced but the difference was not significant.The expression levels of the genes Cla GPAT,Cla GPAT2,Cla GPAT8and Cla GPAT9 under the treatment of 0.25 m M G3P and25%OF were significantly higher in watermelon roots than that in chemical fertilizer treatment.5.Hydroponic experiment was carried out to study the mechanism of G3P and organic fertilizer on the salt stress of watermelon.The results showed that the root supply of G3P,25%OF treatment,and 25%OF with G3P treatment alleviated the inhibition of salt stress on watermelon seed ger mination,significantly increased the dry weight of watermelon above and below ground,significantly reduced MDA content,and increased POD,SOD and CAT.Enzyme activity increases the GPDH enzyme activity and GPAT enzyme activity in roots and leaves,and significantly increases the expression of genes Cla GPDH2,Cla GPDH3 and Cla GPAT,Cla GPAT2,Cla GPAT5,Cla GPAT6,Cla GPAT8,and Cla GPAT9 genes in roots and leaves.And 25%o OF with G3P treatment has the best effect,and it has a stronger ability to alleviate the damage caused by salt stress to watermelon.