Growth, Morphology And Frost Hardiness Of F₁ Genotypes Of Populus × Canadensis Moench Cv. ’Neva’ × Populus Ussuriensis Kom.

Three years old seedlings of 17 hybrid progeny of Populus×canadensis Moench cv.‘Neva’×P. ussuriensis Kom. and their female parent‘Neva’were used to study genetic variation patterns of morphological traits, branch characteristics, leaf microscopic and anatomic traits by using morphologic and anatomical methods. The correlation and regression analysis of all these traits were applied in order to know which traits were kept by superior clones, and whether these traits could be used as the criteria to select good clones. The frost hardiness (FH) of 9 genotypes which had high productivity was assessed by means of the methods of electrical impedance spectroscopy (EIS) and electrolyte leakage (EL). The content of dry matter, soluble sugar, starch, Proline, soluble Protein and Malondialdehyde were measured. All the data were used to estimate correlation with FH in order to choose the offspring which has high FH, and to decide which clones could be used for contrast test in northern and northeastern China.The mean results showed that:1. The height, diameter at breast height, biomass had significant difference between F1 hybrid progeny. Except NK11, NK12, NK55, NK62, NK15, and NK34, all the heights of progeny were above 3 m. All the diameters were above 15 mm, except NK11, NK12, NK15 and NK61. All the offspring’s height and diameter were lower than those of‘Neva’. There was no obvious hybrid vigor to female parent 107. The correlation analysis found that the height and diameter were very appropriate to estimate seedlings of biomass index and also could be used for early superior selection.2. The fresh weight, dry weight, max leaf area, leaf length and width, petioles length, specific leaf area and leaf aspect ratio of leaf showed significant difference between F1 hybrid progeny. The correlation analysis between leaf and biomass discovered that length, width and area of leaf had high correlation with biomass, height and diameter. And the leaf area had highest correlation (r=0.83). Therefore, the leaf area might be used as one of the most reliable indexs for early superior selection.3. The anatomical characteristics of leaf such as length of stomata, number of stomata adaxial, number of stomata abaxial, frequency of stomata, thickness of palisade tissue, spongy tissue, lamina and the ratio of palisade tissue and pongy tissue differed significantly between F1 hybrid progeny with wide variation. Both of the upper and lower epidermis had stomatal distribution, and numbers of upper epidermis were less than those of lower epidermis. The genotypes which grow fast had more stomatas and lower length. On the contrary, the genotypes which grow slower had less stomatas and higher length. All genotypes had the same stomata shape. There was no difference in quality and just number difference was existed.4. The branch characteristics of genotypes had widely variation. Numbers and angle of branch had significant correlation with productivity. The other indexs, however, had no correlation with productivity.5. With the enhancement of the FH, some changes occurred for the EIS parameters and the electrical impedance spectra of shoots and leaves. There was a regularity with the change of the natural temperature that the lower temperature was, the higer FH existed during cold hardening, and the higher temperature the lower FH during dehardening. The level of FH of eight F1 genotypes during cold hardening and dehardening was with a sequence of NK36>NK41>NK61>NK57>NK42>NK60>NK58>NK56, which was superior to Neva. In the strongest level of FH, parts of genotypes could withstand -40℃low-temperature.6. The FH of genotypes measured by EIS and EL methods presented similar tendency. But in the end of frost hardening as well as the beginning of dehardening, the degree of FH estimated by the EIS method was lower than that by the EL method.7. The FH assessed by EIS after artificial freezing treatment correlated to the content of dry matter, soluble sugar and starch, while the Proline, soluble Protein and Malondialdehyde had no significant correlation with EIS parameters.8. The FH of genotypes and the ratio of palisade tissue and pongy tissue (P/S) showed significant correlation. The higher the ratio was the higer the FH. The P/S could be used as one of the most reliable indexs for FH evaluation.