Effects Of Calcium Addition On Salt Tolerance Of Creeping Bentgrass Under NaCl Stress

Saline alkali soil is one of important reserved land resources.Prevention,control of soil salinization,and the development and utilization of saline alkali soil have become the important research categories to promote the sustainable development of economic society and ecological environment.Using exogenous calcium addition to alleviate the salt stress of turf grass and further improving the salt tolerance of creeping bentgrass（Agrostis stolonifera L.）is of great significance for exploring salt tolerance mechanism of A.stolonifer,development and utilization of saline alkali soil in the future and management of turf grass scenery.In this study,four creeping bentgrass clutivars（Impala,Kromi BT,Travel Star,Pen-1（representative A-1））were used as research materials.Three studies were carried out,1)top of paper germination method was used,salt tolerance of four A.stolonifera commercial cultivars（Impala,Kromi BT,Travel Star,Pen-1）under seven kinds of NaCl with different concentration ingredient(0,20,60,120,180,240,300mmol·L^-1),respectively.Germination related indexes,root system and comprehensive analysis by membership function method were determined to evaluating and screening out the salt sensitive varieties and salt tolerant ones;2)The pot experiment of PVC tube was carried out added respectively0,5,10,20,40,60 mmol·L^-1Ca Cl₂and Ca（NO₃）₂under four NaCl concentration gradients(60,120,180 and 240 mmol·L^-1),and select the salt sensitive cultivar and salt tolerant ones.The most appropriate concentration of calcium under different concentrations of NaCl stress was determined by measuring growth related indices and leaf electrolyte permeability of the two varieties;3)Under three concentration gradients of NaCl(60,120,180 mmol·L^-1)stress,the most suitable concentration(5,10,20 mmol·L^-1)of Ca Cl₂and Ca（NO₃）₂which salt stress alleviated was added were set through PVC tube pot experiment,select the salt sensitive cultivar Pen-1,which grew better under the condition of salt stress with calcium added.Two regimes of calcium salt addition were used:foliar spraying and solution adding.To reveal the effects of different application patterns and different concentrations of calcium salt on salt tolerance of creeping bentgrass cultivars under NaCl stress,meanwhile to screen the most appropriate calcium salt addition regime.The main results are as follows:（1）Low concentration of salt stress(20 mmol·L^-1NaCl)promoted the germination of A.stolonifera seeds to a certain extent.Beyond a certain range of salt concentration(60 mmol·L^-1NaCl),with the increase of salt concentration,NaCl stress significantly inhibited the germination and seedling growth of A.stolonifera,each germination related index showed a downward trend with the increase of salt concentration,while salt concentration reached 240～300 mmol·L^-1,seeds hardly germinated;different culatvars of A.stolonifera showed different responses to NaCl stress,among which Impala and Travel Star exhibited better performance,Kromi BT and Pen-1 showed the poorest,the order of comprehensively evaluated salt tolerance was Travel Star>Impala>Kromi BT>Pen-1.（2）Exogenous calcium addition alleviated NaCl stress for A.stolonifera,reduced the electrolyte permeability of seedling leaves.When the NaCl concentration is 60,120,180 mmol·L^-1,and the exogenous calcium addition concentrations is 5,10,20mmol·L^-1,the relief effect is the best;under the stress of various concentrations of NaCl,adding the same concentration of Ca（NO₃）₂and Ca Cl₂,the alleviation effect of Ca（NO₃）₂is better than that of Ca Cl₂,otherwise high concentration of calcium aggravated salt stress on seedlings,and aggravation degree under dual salt stresses susceptible cultivars showed more obvious than that of salt tolerant ones.When the turfgrass suffered from salt stress,application of appropriate concentration while suitable calcium fertilizer addition regime adopted significantly improved the seedling growth of turf-grass,reduced the electrolyte permeability of leaves,alleviated the damage of cell membrane caused by salt stress as well as enhancing the salt tolerance for turf-grasses.（3）Applying exogenous calcium under NaCl stresses.Compared with salt stress alone,foliar spraying of exogenous calcium promoted the growth of seedlings,turf quality increasing,above-ground biomass accumulation,leaf surface area expanding,and foliar spraying of calcium iron the relative water content,soluble sugar content,and chlorophyll content in A.stolonifera under salt stress had a higher increase margin than NaCl stress alone,the relative electrical conductivity,malondialdehyde content and proline content in leaves decreased more under foliar spraying than salt stress alone,indicating that foliar spraying alleviated the salt stress of the aboveground part of A.stolonifera more than solution addition,meanwhile the solution addition had a better promotion effect on the underground biomass,root surface area,root length,main root length,and number of lateral roots of the creeping bentgrass,and alleviated the salt stress of the underground part of A.stolonifera to a great extent.