Comparison of morphological and physiological characteristics of five poplar species in China

Poplars are widely used in scientific research and forestry production due to their traits of fast growth, strong adaptability, and so on. We chose five poplar species as research object, namely, Populus trichocarpa, P. tomentosa, P. canescens, P.×euramericana and P. euphratica, in order to analyze the differences in seedling growth, photosynthesis, microstructure, lignin components and contents of hormones, for a purpose of providing advice for production. Results showed that P. tomentosa, P. canescens and P.×euramericana were elite poplar species in the planting region. They grow faster than the other two species, presumably because they have higher photosynthetic rate yielding more organic compounds, and greater stomatal conductance with high transpiration rate to transport water and inorganic salt efficiently. It suggests that these three species have greater potential in real production. In addition, P. tomentosa has higher lignin content, which might be suitable to be used as building material; In contrast, P. canescens and P.×euramericana have lower lignin content, which might be suitable to be applied in papermaking industry. P. trichocarpa and P. euphratica grow slowly, suggesting that they are unsuitable for production. In addition to effects of photosynthesis and transpiration, their slow growth may also relate to plant hormones. High contents of gibberellins would lead to high degree of differentiation of xylem cells in early growth stage. Furthermore, P. trichocarpa also acts as a model tree in forestry genetic transformation which is very important in scientific research. P. euphratica is tolerant to drought and salinity stresses and is important in environmental protection, which might have relationship with high cis-ABA content, low stomatal conductance, low transpiration rate and little water loss.