Abstract:

A pot experiment was conducted in greenhouse to study the seedling growth and photosynthetic capacity of Populus bachofenii × P. pyramidalis ‘ROZ’ treated with NaHCO₃ in different concentrations for 24 days. The results showed that the NaHCO₃ stress inhibited the seedling growth and leaf photosynthetic capacity. With the increase of stress intensity and of stress time, the height and root-collar diameter increment and total biomass of seedlings, as well as net photosynthetic rate P_n), transpiration rate (Tr) and stomata conductance (G_s) of leaves au significantly decreased. The decrease degree of underground biomass increment was bigger than that of aboveground one. P_n had significantly positive correlationship with Tr and Gs but significantly negative correlationship with stress intensity. The leaf photosynthetic characteristics of P. bachofenii×P. pyramidalis ‘ROZ’ were influenced by stomatal restrictions and non-stomatal restrictions. The decreased of P_n was mainly attributed to stomatal restrictions when the concentration of NaHCO₃ was lower than 48 mmol·L^-1 and to non-stomatal restrictions when the concentration was upper than 48 mmol·L^-1.

Key words: Populus bachofenii ×, P. pyramidalis ‘ROZ’;salinity stress;seedling increment;photosynthetic capability