Physiological Characteristics And Metabolites Of Southern Alfalfa In Response To Salt Stress

The utilization rate of saline-alkali land is low in the eastern coastal areas of our country,while Medicago sativa of southern type has developed and strong roots,strong nitrogen fixation ability and strong growth ability.This study will be the south type shengshi alfalfa 'Millennium' wild type(wild type,WT)and mutant(mutant,MT)as experiment material,after 250 salt concentration,a tendency,L-1 processing after 72 h,determination of wild type and mutant alfalfa root length,the ground and underground part of the dry weight and leaf relative water content,conductivity,the content of chlorophyll,malondialdehyde,reactive oxygen species(H2O2 and O'2)content and activity of SOD and POD enzyme.Metabolites of wild type and mutant alfalfa leaves under salt stress were analyzed by comparing metabolomics with gas chromatography and time-of-flight mass spectrometry(GC/ToF-MS).At the same time,41 different metabolites were selected,and the metabolomics mechanism of salt tolerance changes in the leaves of wild type and mutant of southern alfalfa was revealed.The experimental results are as follows(1)After being treated with 250 mmol·L-1 NaCl for 72 h,the root length,aboveground and underground parts and chlorophyll content of the wild type and mutant alfalfa decreased,and the relative water content decreased significantly.However,the relative conductivity and malondialdehyde content in the leaves of wild type and mutant alfalfa were increased.At the same time,the active oxygen species in alfalfa leaves increased after salt stress,while the increase of wild type leaves was significantly higher than that of mutant.In response to oxidative damage caused by salt stress,SOD and POD activity in leaves increased,but decreased in wild-type leaves,while yellowing in wild-type alfalfa leaves was more serious.It can be concluded that salt stress caused some damage to both wild type and mutant alfalfa,but the mutant showed stronger salt tolerance by enhancing SOD and POD antioxidant enzyme activity(2)The metabolic pathways of wild type and mutant alfalfa leaves in response to salt stress were different.Wild type alfalfa is shown as:a-ketone glutaric acid,fumaric acid,citric acid,maleic acid and succinic acid content increased significantly,strengthen the TCA cycle;The contents of amino acids such as proline,threonine,glutamate,mannose,xylose,trehalose,maltose and inositol in the mutant leaves were increased.It indicated that the wild type under salt stress had increased TCA cycle synthesis of more osmoregulatory substances(proline)and stored energy for its own growth,while the mutant had more osmoregulatory substances to maintain its normal photosynthesis and physiological metabolism,thus being less disturbed by stress.