Effect Of Exogenous BABA On Seed Germination And Seedling Growth Of O.violaeeus Under NaCl Stress

Soil salinization which seriously affects the growth of garden plants,has become an increasingly severe problem waiting to be soleved.Orychophragmus violaceus is widely used in garden forestry.It is a kind of ground cover plant with ornamental value,water and soil conservation capacity,greening environment ability and other good natures.Previous studies have shown that appropriate concentration of BABA can alleviate the harm caused by salt stress on plants.This experiment,adopting Orychophragmus violaceus as the test plant,aims at studying the effects of different concentrations of NaCl(0,12.5,25,50,100,150mmol·L^-1)on seed germination and seedling physiological characteristics;the effects of different concentrations of BABA(0.25,0.5,1.0,2.0mmol·L^-1)on seed germination and seedling physiological characteristics and the effects of seed germination and seedlings physiological characteristics under NaCl stressdifferent concentrations of BABA(0.25,0.5,1.0,2.0mmol·L^-1).The results are as follows:1.In this experiment,NaCl stress reduced the germination rate,germination potential,germination power and seed vigor index of Orychophragmus violaceus seeds,which all decreased with the increase of NaCl stress,and the seed vigor index was 0 at 150mmol·L^-1.NaCl stress reduced the dry mass,fresh mass and root morphological indexes such as root length,root surface area and so on of Orychophragmus violaceus seedlings,and these growth indexes showed a decreasing trend with the increase of NaCl concentration.NaCl stress also inhibited photosynthesis of Orychophragmus violaceus seedlings.Chlorophyll content,Pn,Gs,Fm,Fv/Fm and Fv/Fo decreased with the increase of NaCl concentration.Ci decreased first and then increased with the increase of NaCl concentration,while the Fo increased.The results showed that NaCl stress inhibited seed germination and seedling growth and development.2.In this experiment,with the increase of BABA concentration,the index of seed germination and seedling growth increased first and then decreased.The appropriate concentration of BABA enhanced the photosynthesis of the leaves of Orychophragmus violaceus seedlings.Chlorophyll content,Pn,Gs,Fm,Fv/Fm and Fv/Fo increased and then decreased with the increase of BABA concentration.All the indexs reached the maximum value at 0.5mmol·L^-1,and all the indexs decreased compared with the control at 2mmol·L^-1.Ci showed a decreasing trend with the increase of BABA concentration,while the Fo showed a trend of decline and then rise.The results showed that BABA treatment promoted seed germination and seedling growth and development,while too high concentration of BABA inhibited seed germination and seedling growth.3.The effects of different concentrations of BABA on the index of seed germination,seedling growth,plasma membrane permeability,proline content,antioxidant enzyme activity and chlorophyll content,photosynthetic parameters and chlorophyll fluorescence parameters of Orychophragmus violaceus seedlings under NaCl stress were studied.The results showed that the relative conductivity Orychophragmus violaceus seeding increased firstly and then declined,the biomass,root growth index,proline content,antioxidant enzyme activity and chlorophyll content of Orychophragmus violaceus seedlings declined firstly and then increased With the increasing BABA concentration under NaCl stress.When the BABA concentration was 0.25mmol·L^-1,the soluble sugar and relative conductivity showed the biggest decline.When the BABA concentration was 0.5mmol·L^-1,the soluble proten content,proline content and chlorophyll content revealed the largest increase.The activity of peroxidase and catalase was significantly improved at0.25mmol·L^-1,reaching the maximum value.The activity of superoxide dismutase reaching the maximum value at 0.5mmol·L^-1.Nutrient elements N,P and K reached the maximum value at 0.5mmol·L^-1.Photosynthetic parameters Pn,Gs,chlorophyll fluorescence parameters Fm,Fv/Fm,Fv/Fo reached the maximum value at0.5mmol·L^-1,while Fo reached the minimum value at 0.5mmol·L^-1.The inhibition degree of 2mmol·L^-1BABA addition on seed germination and seedling growth of feueran was higher than that of NaCl alone.It is suggested that 0.25-0.5mmol·L^-1BABA treatment can effectively alleviate the harm of Orychophragmus violaceus seedlings under NaCl stress,and too high concentration of BABA would have adverse effects on seeds germination and seedling growth of Orychophragmus violaceus.NaCl stress inhibited germination of seeds and normal growth of seedlings of Orychophragmus violaceus.The appropriate concentration of BABA could promote the germination of seeds and the growth of seedlings of Orychophragmus violaceus.The application of appropriate concentration of exogenous BABA can alleviate the damage caused by NaCl stress on seed germination and seedling growth of Orychophragmus violaceus.Therefore,the addition of exogenous BABA can be used as an effective measure to improve salinized landscaping land and promote the growth of garden plants.