Studies On The Screening And Physiological Response Under Salt Stress Of Salt-tolerant Watermelon Stocks

Grafting in is an important agricultural technique,Grafting in is mainly used to limit the effects of soil diseases.It has been widely used in such crops as watermelon, melon,cucumber,tomato and eggplant,el al..It plays an important role in the production of horticulture.In recent years,with the cultivation expanded greatly in the greenhouse,the secondary salinization of the soil is becoming worse and has become a leading factor of limiting the sustainable development of vegetable production. Watermelon(Citrullus vulgaris Schrad) is an important vegetable and is widely planted in open field and greenhouse.But because of the effects of soil salinization, Yield and Quality decrease year by year.Therefore,the research of salt tolerance in cucumber is of theoretic and practical significance to direct the production of cucumber and improve the use efficiency of greenhouse.Contraposing the actuality of salt accumulation of soil of protected cultivation becoming more serious in greenhouse,collected watermelon stocks were used as materials in this study to select salt-tolerant stocks suit for greenhouse culture,and its mechanism was studied.The main results as following:1.In the present study,'Feng yuan xian feng','Feng yuan tie jia','Quan neng tie jia','Jing xin zhen NO.1','Jia ren shui gua','Chao feng kang sheng wang' and 'FR'-jiang jun' were chosen as experimental materials.With water culture,we investigated that effects of 90 mmol·L^-1NaCl on the growth,plant height,and stem diameters of stock seedlings.The results showed that:biomass of all shock varieties decreased,plant height and stem diameters were inhibited,net photosynthesis, stomatal conductance of leaves descended,photosynthesis decreased.And the tolerance of salt stress was different in different varieties,'Chao feng kang sheng wang' was the degree of inhibition is smaller,and the tolerance was higher than that of the other varieties.2.The study was conducted in nutrient solution to investigate the effects of NaCl stress on growth,membrane lipid peroxide level,osmoregulation substances, photosynthetic characteristics and of watermelon stocks,including pumpkin cultivar ('Feng yuan xian feng') and calabash cultivar(Chao feng kang sheng wang and FR-Jiang jun).The results showed that the growth of every stock cultivar were restrained NaCl stress.Under NaCl stress plant height,stem thickness,total volume of roots and so on,were lower than those of control.The dry and fresh weight of seedling decreased markedly.All indexes of 'Chao feng kang sheng wang' decreased less than other varieties.Under salt stress,membrane structure was damaged, membrane permeability was increased,relative conductivity was increased significantly,superoxidation of membrane lipid was evidently picked up,and MDA content was increased significantly,so plants were damaged in salt stress.Under NaCI exposure,superoxidation of membrane lipid and injury of 'Chao feng kang sheng wang' was less than other varieties.The net photosynthetic rate and stomatal conductance also decreased,but the content of photosynthetic pigment increased. Photosynthesis was restrained significantly under NaCl stress.Different stocks were different to salt tolerance.Changes of all kinds of indexes in 'Chao feng kang sheng wang' were less than those in 'Feng yuan xian feng' and 'Jiang jun'.Under salt stress, K⁺,Ca²⁺ content decreased,Na⁺ and Cl^- content increased in stock,and Na⁺ and Cl^-content in leaves and roots of 'Chao feng kang sheng wang' increased less than 'Feng yuan xian feng'and 'FR-jiang jun',but the absorbency of K⁺,Ca²⁺ were stronger than other varieties.So the results were favor of maintaining natural physiological activities and higher photosynthesis.And all that suggested 'Chao feng kang sheng wang' suffered the least salt stress and had the best salt tolerance in all watermelon stocks in our experiment.The results indicated that effects of salt stress on stock varieties were different,under salt stress,the growth of 'Chao feng kang sheng wang' inhibited less,the osmotic adjustment ability and photosynthesis was higher than that of 'Feng yuan xian feng'and 'FR-jiang jun',and the injury of plant was smaller and had stronger the salt of tolerance.3.Salt-tolerance of 'Chao feng kang sheng wang' as the stock and 'xiu li' as the scion was chosen as experimental material,and we studied that the effects of 100 mmol·L^-1 NaCl stress on the growth,photosynthetic parameters,photosystemâ…¡photochem(PSâ…¡) and K⁺,Na⁺,Ca²⁺,Mg²⁺,Cl^- content in different apparatus of grafted seedlings and scion-root seedling.Main researches were as follows: 1)Salt stress decreased significantly the growth,net photosynthesis(Pn),stomatal conductance(Gs),tercellular CO₂ concentration(Ci),actual efficiency of PSâ…¡(ΦPSâ…¡) and efficient of photochemical quenching(qP) of grafted seedlings and scion-root seedling,but had less effects on the maximal photochemical efficient (Fv/Fm).The grafted seedlings were significantly inhibited than the scion-root seedling in the equal salt stress.2) Na⁺,Cl^- content of grafted seedlings and scion-root seedling increased significantly for 9 days in NaCl stress,but that of grafted seedlings was advanced less than that of scion-root seedling,and this could reduce that effects of excessive Na⁺,Cl^- content on photosynthesis and physiological,biochemical activity.The content of K⁺,Ca²⁺,Mg²⁺ in grafted seedlings and scion-root seedling was decreased,but K⁺,Ca²⁺,Mg²⁺ content of grafted seedlings was higher than that of scion-root seedling,this indicated that grafting advanced the choice,movement of K⁺ and Ca²⁺,and improved the effects of excessive Na⁺ on injury in a certain extent.