Salt Tolerance Identification Of Ginger And Mitigation Effect Of Exogenous Silicon On Salt Stress

Ginger（Zingiber officinale Roscoe.）is a medicinal and edible vegetable and export agricultural products with high output,large market demand and good economic benefits,which is a special and efficient industry for the revitalization of rural areas in our country.In recent years,due to the increase of planting years and serious soil salinization in some main ginger producing areas,the yield and quality of ginger decreased obviously,which hindered the healthy development of ginger industry.Si（Silicon）is involved in the growth and stress response in plant,and plays a positive role in promoting plant growth and resistance to stress.However,there are few studies on the salt tolerance of ginger,the indexes and methods for evaluating the salt tolerance of ginger are lack of reference,and the salt tolerance mechanism of Si in ginger is not clear now.So this study identified and evaluated the salt tolerance of five main ginger cultivars（Shandongdajiang,Fengtoujiang,Zhugenjiang,Guizhouhuangjiang and Luopingxiaohuangjiang）,in order to explore excellent resistance germplasm and select salt tolerance indicators;on this basis,to further explore the mitigation effect of SiNPs on ginger salt stress.The results of the study are as follows:1.Identification methods and evaluation indexes of salt tolerance of ginger.Five ginger cultivars were selected to determine the growth morphological characteristics and physiological and biochemical indexes of ginger seedlings under salt stress.The results showed that under salt stress,the leaves of ginger seedlings were yellowed,the increase of plant height,stem diameter and leaf number,root vitality,water potential and osmotic potential decreased,while the contents of malondialdehyde（MDA）and H₂O₂ increased,and the activities of antioxidant enzymes（superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）and phenylalaninammo-nialyase（PAL））also changed.The results of principal component analysis,membership function analysis and comprehensive evaluation showed that the order of salt tolerance of five ginger cultivars was Shandongdajiang>Guizhouhuangjiang>Fengtoujiang>Luopingxiaohuangjiang>Zhugenjiang.The results of correlation analysis showed that there was a very significant positive correlation between root vitality and comprehensive evaluation value D value,and a significant positive correlation between the increase of plant height,stem diameter and leaf number and D value.Root vitality and the increase of plant height,stem diameter and leaf number can be used as the main reference indexes for screening and identification of salt-tolerant ginger cultivars.2.Physiological and biochemical mechanisms of exogenous Si in alleviating salt stress in ginger.The leaves of ginger seedlings were sprayed with 100 mg·L^-1 SiNPs solution at first,and then treated with salt stress after 5 days.The growth morphology,photosynthetic characteristics,membrane lipid peroxidation,antioxidant enzyme activities and ion contents of ginger seedlings under salt stress were measured.The results showed that under salt stress,the leaf yellowing symptoms of ginger seedlings treated with SiNPs were alleviated,and total root length,root surface area and root tip number were significantly increased,chlorophyll a（Chl a）,chlorophyll b（Chl b）and chlorophyll a+b（Chl a+b）contents,maximum photochemical efficiency（F_v/F_m）,actual photoquantum efficiency（ΦPSII）and photochemical quenching coefficient（q P）,net photosynthetic rate（P_n）and transpiration rate（T_r）,SOD,POD and CAT activities,K⁺contents in roots,stems and leaves were significantly increased,while non-photochemical quenching coefficient（NPQ）,MDA and H₂O₂ contents,Na⁺contents in roots,rhizomes,stems and leaves were significantly decreased.The results showed that the order of salt tolerance of 5 ginger cultivars was Shandongdajiang>Guizhouhuangjiang>Fengtoujiang>Luopingxiaohuangjiang>Zhugenjiang.Root vitality and the increase of plant height,stem diameter and leaf number can be used as the main reference indexes for the selection of salt-tolerant ginger cultivars.Exogenous SiNPs treatment alleviated the adverse effects of salt stress on ginger seedlings by promoting root growth,increasing photosynthetic pigment contents,enhancing photochemical activity of PSⅡreaction center,improving photosynthetic efficiency,regulating antioxidant enzyme activities,reducing cell membrane lipid peroxidation,reducing Na⁺accumulation and promoting K⁺transport and redistribution.