Propagation And Cold Resistance Of Improved Hybrid Clones For Populus

In this paper, the new poplar clones were used as experimental materials, including Populus×canescens (Ait.) (L4, L2); Populus tremula L.×P. tremuloides / Brauna×Tur141 (E4, E2). Plantlet regeneration, growth and photosynthetic characteristics were studied respectively. After comparing with Populus tomentosa Carr., Populus×euramericana cl. Zhonglin46. and Populus szechuanica Schneid. var. tibetica schneid., the new poplar clones were ordered in cold resistance.The main methods include electrical impedance spectroscopy method (EIS method), electrolyte leakage method (EL method) and determination of the relevant physiological indicators including POD activity, SOD activity, MDA content, soluble protein content, soluble sugar content and proline content. The cold resistance was determined. It was the basis for the introduction.The main results as follows:1. With the 6-BA concentration increased, the differentiation rate of L4 and L2 gradually decreased and the differentiation rate of E4 and E2 increased at first and decreased then. The plant height decreased with the 6-BA concentration increased, but the vitrification phenomenon was observed on proliferation shoots. When the 6-BA concentration at the same level, the differentiation rate declined as IBA concentration increasing. The results showed that the optimum propagation culture medium of L4 and L2 was MS +6-BA 0.3 mg·L^-1 +IBA 0.1 mg·L^-1, the medium of E4 and E2 was MS +6-BA 0.5 mg·L^-1 +IBA 0.1 mg·L^-1.2. For L4 and L2, with the IBA concentration increased the main roots shortened gradually, and the lateral roots increased at first and decreased then; As the NAA concentration increased, the main roots were shorter and shorter, the phenomenon of the hairy roots and callus were more and more serious. For E4 and E2, the roots in the medium with the NAA were usually shorter, and with the NAA concentration increased, the plant callus were observed at the base of the plantlet, and the callus bigger and bigger. The roots from medium with IBA were longer than from NAA, with the IBA concentration increased, lateral roots increased gradually. The results showed that for L4 and L2, the rooting culture medium was 1/2MS +IBA 0.3 mg·L^-1; for E4 and E2, the rooting culture medium was 1/2MS +IBA 0.5 mg·L^-1.3. The transplanting survival rate of the clones reached 95.0 %, and the planting survival rate was more than 90.0 %. All seedlings grew well.4. The fast-growing of seedlings is 7 to 8 months. Comparing with annual growth, the high-growth is 34 % to 40 % in 7 to 8 months. And the specific ratio varies by plant species, but little difference between the clones. In diameter growth also showed the law.5. For clones L2, E2, the process of photosynthesis curve increased at first and decreased then, the curve showed a single peak curve, the peak appeared at 14:00, 12:00. For clones L4, E4, the curve showed a bimodal curve, the second peak appeared about 8:00, then at 12:00, 10:00 appeared the peak.6. For all clones, the curve of transpiration rate showed a asymmetrical bimodal curve. The peak appeared around 10:00, then at 14:00 the second peak appeared.7. Specific intracellular resistance ( ri ) is the most suitable parameter of EIS method for Populus.8. Using EIS method analysis, ri of all clones increased with the decreasing of treatment temperatur and showed a special " S " curve. Parameter ri was negatively correlated with the treatment temperature. The relative conductivity also showed the law. Between EIS method and EL method exists correlation.9. Parameter ri by Logistic equation was obtained for LT₅₀, which is an indicator of cold resistance. With LT₅₀, the cold resistance order of new poplar clones: Populus szechuanica Schneid. var. tibetica schneid. > E4 > E2 > Populus×euramericana cl. Zhonglin46. > Populus tomentosa Carr. > L4 > L2.10. Relative conductivity by Logistic equation was obtained for LT₅₀, With LT₅₀, the cold resistance order of new poplar clones: Populus szechuanica Schneid. var. tibetica schneid. > E4 > E2 > L2 > L4 > Populus×euramericana cl. Zhonglin46. > Populus tomentosa Carr..11. Difference was observed between LT₅₀ from EIS method and EL method. EL method was significantly lower than EIS method.12. Analysising the membership function of POD activity, SOD activity, soluble protein content, soluble sugar content, proline content, the cold resistance order of new poplar clones: Populus szechuanica Schneid. var. tibetica schneid. > L4 > E2 > E4 > Populus×euramericana cl. Zhonglin46. > Populus tomentosa Carr. > L2.13. In order to ensure the scientific results, combining with the field growth in the cold and comprehensive analysis, the final cold resistance order: Populus szechuanica Schneid. var. tibetica schneid. > E4 > E2 > L4 > L2 > Populus×euramericana cl. Zhonglin46. > Populus tomentosa Carr..