Study On Salt-resistant Characteristics And Mechanism Of Clone Seedlings Of Taxodium Hybrid

Four clones of one-year-old cutting seedlings of Taxodium hybrid were used as the tested materials. We designed a new salt treatment method in this research. The effects of NaCl stress on morphological and physiological indexes of T. hybrid clones were studied. We also discussed the mechanism of salt tolerance of T. hybrid seedlings and compared the ability of the salt tolerance of the 4 clones.The data of the experiments showed that salt concentrations from 125mM to150 mM were the critical salt concentrations of T. hybrid seedlings and 100mM to 125 mM were more effective treating concentrations to select salt-tolerance materials from T. hybrid clones. The effects of salt stress on morphological and physiological indexes of 4 clones were different. The terminal bud of seedlings was more sensitive to salt stress. The growth of terminal buds was restrained under the low concentration of salt treatment or died under high salt concentration. The lodging percentage and the lateral bud percentage increased when the effect of apical dominance was inhibitted or disappeared. The type of stems was destroyed badly. So this index should be taken as an important index of salt tolerance evaluation for T. hybrid clones.Height increment, biomass accumulation and Pn had been inhibited under NaCl stress. There was no significant difference on the leaf relative water content and the leaves were green and healthy when the NaCl treating concentration was 125 mM. There was no significant influence of salt stress on leaf plasma membrane permeability. Clones 118 and 146 were good at accumulating Na⁺ in roots and reducing the movement of Na⁺ from roots to leaves to alleviate the Na⁺injury effect on leaves. Ca²⁺ and Mg²⁺ contents increased in both of roots and leaves. Activity of SOD increased continuously, while the activity of POD rose only at the beginning of the treatment and the activity of CAT raised firstly then dropped. With the increament of NaCl treating concentration and the stress time, the soluble sugar content and proline concentration increased continually. The soluble protein content decreased after long time treatment under high salt treating concentration.The order of salt tolerance capacity of the four clone seedlings were 118>146>1>302. The process of the promotion effect in plant growth under low salt stress was discussed. The growth of the terminal buds was restrained under the low concentration of salt treatment and the effect of apical dominance also inhbitted. So the seedlings grew quickly at the beginning phase of the salt treatment.