Response in growth and ionic distribution of elm clones under NaCl stress

Elm is the most important potential afforestation species in coastal saline soil. Taking Ulmus pumila clones EC7 and EC51 as experimental materials, the growth conditions of 2 clones and accumulation characteristics of Na⁺, Cl^- and K⁺ in each organ were studied under 5 kinds of NaCl concentrations (0, 50, 85, 120 and 155 mmol/L) with the method of pot experiment for exploration of ion distribution, accumulation characteristics and the response to NaCl in each organ of elm clone. Theory basis was provided for introduction and cultivation of elm clone in coastal saline soil with comparison between salt tolerance capabilities of two clones. Results showed that:1) under the condition of salt stress, salt damage symptoms of elm clone such as etiolated and withered leaves will aggravate with the increase of concentration, and under high salt concentration stress of 155 mmol/L, EC7 plant died while EC51 didn't. Under the same NaCl concentration, salt damage symptom of EC7 was more serious than EC51; NaCl stress had inhibited biomass accumulation of elm clone obviously and inhibition phenomenon on the ground was more obvious. Under the stress of salt concentration more than 50 mmol/L, biomass in each part of EC7 decreased (P < 0.05) significantly while biomass change of EC51 was more stable with stronger adaptability. 2) Contents of Na⁺ and Cl^- in each organ of EC7 and EC51 increased with the increase of salt concentration, and distribution characteristics of Na⁺ was root > stem > leaf while that of Cl^- was root > leaf > stem. Under the stress of salt concentration more than 85 mmol/L, increasing amplitude of Na⁺ content in each organ of EC51 was smaller than that of EC7 and Cl^- accumulation in root was more than that in leaf for EC51, while Cl^- accumulation in leaf was more for EC7. Ion distribution mode of EC51 had reduced accumulation of salt damage ions in photosynthetic organ and Cl^- content in stem was the minimum. Thus, it can be deduced that stem organ may be just a transmission channel. 3) K⁺ content in each organ decreased significantly compared with the contrast and the decreasing amplitude of EC7 was greater, especially in root and leaf. Under the salt concentration more than 85 mmol/L, K⁺ content change in EC51 was relatively stable and K⁺ content in each organ of EC51 was higher than that of EC7, and the rate of K⁺/ Na⁺ in stem and leaf of EC51 was higher than that of EC7 under the same concentration, indicating that EC51 had better adaptability in hypertonic environment with salt stress. Research indicated that elm clones EC7 and EC51 had certain salt tolerance capabilities and can grow well in environment with salt concentration less than 85 mmol/L, while EC51 had stronger salt tolerance capability than EC7 under the stress condition of salt concentration more than 85 mmol/L.