Studies On Drought And Saline-alkali Tolerance In Sect. Populus Clones At Nursery Stage

Species of Section Leuce were common used as the main sylvicultural tree species in arid and semi-arid areas in the northern and northwestern of China, and important industrial timber species. They have been playing a significant role in the ecological forestry and the the people's livelihood forestry. a theoretical basis for the study of poplar of stress resistance ability was necessary to evaluate the adaptive of poplar and determine the scope of the promotion of cultivation. The growth and physiological characteristics of white poplar clones grown in pots under different drought stress and NaHCO3 stress were investigated. The results were as follow.1. The increment of height, basal diameter and biomass, and root-shoot ratio of clones had significant differences among 9 clones. The two clones 89 and YX2 showed the fast-growth. The chlorophyll content increased under mild water stress, but then decreased rapidly under moderate and severe water stress, and the chlorophyll content of clone 89 and YX2 showed the smallest decline under drought stress. The contents of the free proline and the soluble sugar in 9 clones showed the trend of increasing gradually with the development of soil drought, and that of clone Z3, YX2 and 89 was significantly higher than the other clones. The cell membranepermeability and MDA content had a steady increase with the soil water content gradually reducing, and that of clone Z3, YX2 and 89 was significantly lower than others under the same drought condition. The activities of SOD increased under light and moderate water stress, and then decreased under severe water stress. The activities of SOD in clone 89 and YX2 were always higher than that in control.2. The growth of above-ground and root were inhibited apparently under NaHCO3 stress. The two clones 26 and 89 showed the fast-growth. The chlorophyll content decreased obviously in all clones, and the chlorophyll content of clone 26 and 89 showed the smallest decline under NaHCO3 stress. The content of the proline in 8 clones showed the trend of increasing gradually with the increase of NaHCO3 concentration, and that of clone 26 and 89 was significantly higher than the other clones. The cell membrane permeability and MDA content had a steady increase with the increase of NaHCO3 concentration, and that of clone 26, LM50 and 89 was significantly lower than others under the same stress. SOD activity first increased and then decreased, and that of clone 26 and 89 was always higher than the other clones.At a concentration of NaHCO3 was 90 mmol·L-1, the height increment and the basal diameter increment had a significantly correlation with all the physiological indexes. It indicated that using the growth and physiological indexes to evaluate the salt-resistance of eight clones could therefore reflect the response of NaHCO3 stress.3. Comprehensive assessments of drought resistance based on the principal component analysis and subordinate function values analysis indicated that the sequence of drought resistance in nine clones from high to low was as follows: 89, YX2, LM50, Z3, Y3, 150, 27, 26, and 1316. Through principal component analysis, the sequence of salt resistance in eight clones was 26>89>LM50>150>Z3>27>1316>Y3.