Research On Drought Resistence Of New Hybrid Clones Of Populus Deltoids×Section Tacamahaca

Poplar is one of the important cultivated species in north of China. It is an important field in genetic breeding to carry out drought resistance breeding of poplar. It is so dry in the north part of our country that many plants grow hard, especially in the northwest area. Doing research on drought resistance characteristics of poplar and then cultivate new poplar varieties with stronger drought resistance is necessary to expand the scope of distribution and cultivation of poplar, and get great poplar productivity. What’s more, the cultivation of new poplar varieties is of great significance for the construction of the ecological environment in northern China. In this research, new hybrid poplar clones of P. deltoides x P. cathayana and two referential cultivars(Shaanxi NO.4 and Zhongsui12) were used as materials to investigate drought resistance. The leaf anatomical structures were observed with paraffin sectioning method. The physiological and biochemical indicators of seedlings of poplar were measured through artificial potted water control experiments. And then a comprehensive evaluation on drought resistances of poplar clones were gived by the method of subordinate functions, which could provided scientific basis for cultivating new poplar varieties with stronger drought resistance and determining suitable scope. The conclusions were as follows:1. The leaf anatomical structures were observed with paraffin sectioning method on eight poplar clones, including six new poplar clones(06-69×P. szechuanica 1, 06-57×P. szechuanica 1, 06-69×P. cathayana 1, 07-69×P. cathayana 1, 06-69×P. purdomii 1, 07-west da-zhai×P. purdomii 1), and two referential cultivars(Shaanxi NO.4 and Zhongsui12). Ten xeromorphic indices were measured, such as thickness of leaves, thickness of vein, cuticle thickness, thickness of upper and lower epidermis, thickness of sponge tissue, thickness of palisade tissue and thickness ratio of palisade tissue to spongy tissue and so on. The three typical xeromorphic indices including thickness of leaves, thickness of vein, thickness ratio of palisade tissue to spongy tissue were selected by variance analysis and principal component analysis. And then a comprehensive evaluation on drought resistances of eight poplar clones was gave by the method of subordinate functions. The conclusion showed that the the drought resistance capabilities of eight poplar clones were in the order of 07-69×P. cathayana 1, 06-57×P. szechuanica 1, Shaanxi NO.4, 07-west da-zhai×P. purdomii 1, Zhongsui12, 06-69×P. szechuanica 1, 06-69×P. purdomii 1, 06-69×P. cathayana 1.2. Using four 1-year-old new poplar clones(06-57×P. szechuanica 1, 07-69×P. cathayana 1, 06-69×P. purdomii 1, 07-west da-zhai×P. purdomii 1) and two referential cultivars(Shaanxi NO.4 and Zhongsui12) as materials, we studied the effects of different degrees of water stress on seedlings growth and physiological indicators of six poplar clones(species) through artificial potted water control experiments. The results indicated that with the aggravation of water stress, the seedling height, ground diameter, biomass, root biomass, leaf biomass, stem biomass, leaf area for photosynthesis, net photosynthetic rate and leaf relative water content of the six seedlings decreased significantly; the content of free proline in leaves increased significantly and soluble protein decreased significantly; the content of malondialdehyde(MDA) and relative electrical conductivity in leaves were increased significantly; the activities of superoxide dismutase(SOD) and peroxidase(POD) increased at beginning and then dropped under severe water stress, but the activities of two protect enzymes were always higher than those under normal water condition. The adaptability and productivity of the six poplar clones(species) under water stress were contrasted and analyzed. The drought resistance capabilities of six poplar clones(species) were comprehensive evaluated with subordinate function, their drought-resistance order was 07-69×P. cathayana 1, Shaanxi NO.4, 06-57×P. szechuanica 1, 06-69×P. purdomii 1, Zhongsui12, 07-west da-zhai×P. purdomii 1.