Studies On Salt Tolerance And Mitigative Effect Of Exogenous Hormone On Salt Stress Of Strawberry Plantlets In Vitro

The aim of the experiment was to research salt tolerance of strawberry plantlets and to study the mitigative effect of three kinds of exogenous hormone on growth of strawberry plantlets under certain salt stress in vitro by comparing some growth indexes and physiological indexes.Strawberry plantlets of eight varieties were inoculated in medium with 0, 0.1 percent, 0.2 percent, 0.3 percent or 0.4 percent NaCl. After 15 days of in vitro culture, their growth was investigated. The results were as follows: the growth of strawberry plantlets under salt stress was inhibited. And the physiological indexes of strawberry plantlets were also affected. The content of chlorophyll and soluble protein of strawberry plantlets' leaves decreased, but the content of proline and malondialdehy (MDA) produced by lipid peroxidation increased. The activity of membrane protective enzymes was also affected. The activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) declined with the increase of the level of salt concentration. The changes of indexes were regarded as the useful physiological indexes to study salt resistance in strawberry plants. These varieties could be divided into three groups: the varieties of X and JX belonged to the group of salt tolerance, JZ,Q and CX belonged to the group of salt sensitive varieties and the moderately tolerant group included varieties of CTT and D.The results also showed that physiological indexes of the strawberry plantlets changed obviously when the concentration of NaCl in medium was more 0.3 percent. So it could be concluded that 0.3 percent of NaCl was a critical value in studying on salt tolerance of strawberry.The effect of exogenous hormone on salt resistance of strawberry plantlets to saline environment with 0.3 percent was studied in vitro. The results indicated that compared with those which grew under salt stress, the treatment with 0.5mg/L GA3 relatively promoted the number and the length of roots, enhanced the height of strawberry plantlets, increased the number of leaves and the ratio of buds' division. And the content of chlorophyll, praline and soluble protein was relatively increased, the accumulation of MDA was comparatively delayed, the activity of SOD, POD and CAT was relatively promoted. l.Omg/L IAA also promoted the growth of strawberry plantlets, raised the content of chlorophyll, proline and soluble protein ,declined the content of MDA, promoted the activity of SOD, POD and CAT, mitigated the salt stress injury. The medium with 0.5mg/L 6-BA promoted the growth of strawberry plantlets, increased the content of protein, proline and chlorophyll, decreased the content of MDA, enhanced the activity of SOD, POD and CAT, but the rhizogenesis had been hindered. The mitigative effect of GA3 on salt stress was the best, then the IAA, and then the 6-BA.