Study On The Effects Of Salt Stress On 13 Tree Species

The 13 tree species have been studied on the growth, morphological, physiological and biochemical characters under salt stress. The one-year-old seedlings of them grown in pots were tested by applying 0. 2%, 0. 4%, 0. 6% NaCl solutions for 12 days, 24days, 36 days and 48 days, respectively. During different the stress period, the height, the electrolyte leakage, the content of Pro and soluble protein and soluble sugar and MDA, the content of chlorophyll and chlorophyll a and chlorophyll b, and carotenoid, the activities of SOD and POD were studied. Based on the results, the salt resistant capacity and mechanisms of different growth period of different tree species were identified. At the end of the experiment, the biomass, root activity and the content of Na+, K+ were determined. Comprehensive analysis has been made for these 22 characters in order to reveal the internal mechanisms. Particularly the correlation of the root and the above were emphasized. According to the above studies, the scientific basis for the research on salt resistance mechanism are provided. The main results are as follows.Among the indexes measured salt resistant capacity, the survival capability is dominant factor. The survival percents of seedlings were decreased under salt stress. The levels of salt resistance of those 13 tree species from high to low are: Ailanthus altissima (Mill) Swinge, Robinia pseudoacacia L. or Ulmus pumila L. or Fraxinus chinensis Roxb., Sapium sebiferum (L.) Roxb, Melia azedarach L., Hibiscus syriacus L., Koelreuteria paniculata Laxm., Salix matsudana Koidz or Cotinus coggygria Scop., Diospyros lotus L., Cere is chinensis Bunge, PIatanus oriental is L..Growth of 13 tree species were inhibited and the difference among NaCl concentration were more significant with the stress time.The symptoms of the leaves also displayed the same trend.With the increasing of salinity concentration, the biomass and the area of leaf were decreased distinctly. The ratio of stem to root weight of Ail an thus altissima (Mill) Swinge, Robinia pseudoacacia L., Melia azedarach L., Ulmus pumila L., Hibiscus syriacus L, Cere is chinensis Bunge, Koelreuteria paniculata Laxm., Cotinus coggygria Scop., Diospyros lotus L.and Salix matsudana Koidz failed that indicated the stem were sensitive to salt stress.The ratio of stem to root weight of Sapium sebiferum (L.) Roxb, Platanus orientalisL.and Fraxinus chinensis Roxb. were not subject to salt stress.The electrolyte leakage increased, the chlorophyll decomposed, the absorption area of the root, the activity of the root and the photosynthesis descended under salt stress. To most tree species, the correlation and the SOD, POD, Pro, soluble sugar and soluble protein were not obvious. By comparison to chlorophyll, chlorophyll a and chlorophyll b carotenoid were the least susceptible to salt stress. During the whole salt stress, the relations among SOD and soluble protein and soluble sugar were positive, the relation between Pro and electrolyte leakage were negative. The relations of cartooned and chlorophyll, chlorophyll a , chlorophyll b were positive, showing that cartooned was beneficial to them.The indexes of electrolyte leakage, chlorophyll, the root activity and the absorption area of the root could be adopted to assess the resistant salt ability of tree species. The union of the survival ability, the growth, morphological, physiological and biochemical characters was important to judge the capability of tree species.By means of the main components analysis, the dominant factors that determined growth are not the same. Stress of 12 days, the firstcomponent was chlorophyll; the second component was soluble protein. Stress of 24 days, 36 days, was chlorophyll, electrolyte leakage; chlorophyll, MDA. Stress of 48 days, the first component was chlorophyll, the second component was Pro, the third was SOD. At any period, the chlorophyll was closely related to growth.Through the multiple regression of biomass and morphological, physiological, biochemical characters, the decent of t...