Effect Of Sodium And Chloride Salt Stress On The Growth And Photosynthesis Of Sweet Potato Seedlings

In order to screen the variety which was the most resistant to salt soil, foursweetpotato cultivars (in the area of Shandong and Jiangsu province) were used toexamine their salt tolerance at stage of seedlings. Jishu21was the salt tolerant cultivarand Shengli Baihao was the salt sensitive one. And we performed the followingexperiment with these two varieties: the comparied with the effect of Na⁺and Cl^-treatments on different sweetpotato seedlings, effect of different concentration Cl^-treatments on the growth and the photosynthesis of these two sweetpotato cultivars,Effects of chloride channel blockers on the growth and the photosynthesis of them underNaCl stress. As one of the common chlorine-sensitive crops, it had very importantpractical values to research the Cl-stress response and the resistance to chlorine poison ofsweet potatoes under salt stress, meanwhile it was significant to proclaim salt-tolerantmechanism and to improve the salt-tolerance of sweet potato. The main results are asfollows:1. The screening of salt tolerance among different varieties of sweet potato seedingsThe yellow leaf rate, the death rate, the salt injury rate, the salt injury index, therelative stem length, the fresh and dry weight of seedlings were investigated under0mmol/L and150mmol/L NaCl. The results showed that the most salinity tolerant varietywas Jishu21and the most salt sensitive variety was Shengli Baihao.2. Comparative study on effect of Na⁺and Cl-salt stres on growth andphotosynthesis of sweet potato seedingsThe effects of iso osmotic NaCl﹑Na⁺and C1^-(150mmol/L) stress on the relativegrowth and the photosynthesis of two genotypes of sweet potato seedlings wereinvestigated. The results showed that the growth of C1^-salt-stressed seedlings was theworst. In addition, the fresh weight, dry weight and plant height were the smallest amongthe four different treatments (control, iso osmotic NaCl﹑Na⁺and C1^-(150mmol/L). The growth and photosynthesis of two cultivars seedlings were both severely affected.Moreover, the growth inhibition of C1^-salt-stressed seedlings was more serious thanNaCl and Na+salt, and there was no obvious difference between NaCl and Na⁺salt-stressed seedlingss. Therefore, it is concluded that sweet potato is a C1^-sensitivecrop.3. Effects of exogenous chloride on growth and photosynthesis of sweet potatoseedlingsThe growth of sweet potato seedlings was little inhibited when Cl^-is lower than75mmol/L. However, the fresh and dry weight, net photosynthetic rate and chlorophyllcontent were significantly declined under condition of150-220mmol/L Cl^-treatnets.High concentrations of Cl^-salt streaa led to toxic effects on the plants, seriously affectedthe growth of sweet potato seedlings.The Cl^-contents in different tissues of sweet potatoseedlings were: stemï¹¥old leavesï¹¥yong leavesï¹¥roots. More than65%Cl^-accumulatedin the stem and old leaves to reduce the chlorine damage to yong parts such shoot tip andyong leaves, which is perhaps one of the mechanisms adapting to chlorine hurt of sweetpotato seedings.4. Effects of chloride channel blockers on the growth and physiological indexes ofsweet potato seedlingsCompared to the control (NaCl), Both K+and NO3-content in the seedlingsincreased, while Cl^-content decreased under condition NaCl+20μmol/L Zn²⁺.Oppositive results were obtained under condition NaCl+20μmol/L Nif. The MDAcontent of seedlings leaves decreased obviously, chlorophyll content increasedsignificantly. These results suggested that Zn²⁺has certain alleviating effects on chlorinedamage of sweet potatoes but Nif is enhanced this damage. This further supports thatsweet potato is a chloride-sensitive plant.