Objective To reveal the regulatory effects of chromosome doubling on the growth, physiology and wood properties of Populus hopeiensis by comparing the differences in growth, physiological and wood properties between diploids and their autotetraploids.

Method Taking one-year-old diploids and their corresponding autotetraploids derived from different genotypes (BT1, BT3, BT8) as the research objects, we measured the plant height, basal ground diameter, internode length and leaf traits. Photosynthetic parameters such as net photosynthetic rate and transpiration rate were determined by using a LI-6400. The lignin and cellulose content of seedling stems were estimated via the two-step acid hydrolysis method combined with high-performance liquid chromatography and ultraviolet-visible spectroscopy.

Result (1) The plant height and basal ground diameter of the autotetraploids were lower than those of the diploids, while the internode length of the autotetraploids was higher than those of the diploids. The leaf length, leaf width, leaf area and leaf thickness of the autotetraploids were higher than those of the diploids, while the leaf length-width ratio of the autotetraploids was lower than those of the diploids. (2) The net photosynthetic rate of the autotetraploids was higher than that of their corresponding diploids, while the transpiration rate, stomatal conductance and intercellular CO₂ concentration of the autotetraploids were lower than those of the diploids. (3) The lignin content of the autotetraploids was lower than that of their corresponding diploids, while the cellulose content of the autotetraploids was higher than that of the diploids. (4) Ploidy level had an extremely significant effect on the plant height (P < 0.001), basal ground diameter (P < 0.001), internode length (P < 0.001), leaf length (P < 0.001), leaf width (P < 0.001), leaf length-width ratio (P < 0.001), leaf area (P < 0.001), leaf thickness (P < 0.001), lignin content (P < 0.001) and cellulose content (P < 0.001) of one-year-old Populus hopeiensis seedlings.

Conclusion Chromosome doubling has significant effects on the growth, physiological and wood properties of forest trees in Populus hopeiensis. The results play an important role in the recognition of gene dosage effects on the development and timber formation.