Research On Response And Assessments Of Several Introduced Tree Species To Salt Stress

This thesis, based on the first year stump seedlings of five introduced tree species, with potted and hydroponic salt stress method, observed the responding mechanism to salt stress of the five introduced tree species from the change of the cell organelle's ultrastructure, features, physiology, biochemistry reaction etc, and evaluated the salt tolerance of the five introduced tree species. Main research findings are as follows:1.Investigation on potted plants under salt stress shows that salt tolerance of the five introduced tree species is different, there are three grades of salt tolerance, the order is as below: Fraxinus americana, Gleditsia triacanthos> Alnus rubua > Nyssa aquatica, Acer Ginnala Maxim.2. Salt stress restrains the growth of the relative diameter and relative height of the five introduced tree species. It also restrains the photosynthesis of each tree. With the increase of salt stress degree, net photosynthetic rate(Pn), stomatal conductance(Cond) and transpiration rate(Tr) of each tree decreases, while intercellular CO2 concentration(Ci) increases. Fv/Fm,ФPSⅡare lower than control, the chlorophyll content decreases. Salt stress increases the cell membrane permeability. With the increase of salt stress degree, RWD becomes more obvious than the control and osmoregulation substance of praline increases.3. Research on potted and hydroponic salt stress shows that with the increase of salt stress degree and processing time, MDA content increases, while sod activity, soluble protein and soluble sugar all increases first and then decreases and are lower than the control under heavy salt stress.4. Observation of the ultrastructure shows that the influences of membrane structure on Alnus rubua, Fraxinus americana, Gleditsia triacanthos are small while the influences on Nyssa aquatica, Acer Ginnala Maxim. are big.5. The salt tolerance of the five introduced tress species was evaluated by applying the combined method of datum transformation of coordinate systems. The order of salt tolerance is as below: Fraxinus americana, Gleditsia triacanthos> Alnus rubua > Nyssa aquatica, Acer Ginnala Maxim. Cluster analysis shows that the first type includes Fraxinus americana and Gleditsia triacanthos, whose salt tolerance is strong, the second type includes Alnus rubua, whose salt tolerance is average, the third type includes Nyssa aquatica, Acer Ginnala Maxim, whose salt tolerance is poor.