Abstract:

Net photosynthetic rate(P_N) and growth of seedlings in poplar, walnut, velvet ash and pagoda tree, which were cultured in moist vermiculite with a range of NaCl concentration from zero to 200 mmol/L in glasshouse, were determined. In contrast to that of pagoda tree, the survival percent of poplar ′Zhonglin－46′was the least. The survival percent of walnut was more than that of velvet ash. Dry weight and leaf total area decreased to different degree after salt treatment. It was obvious that P_N of the four tree species different responded to salinity and the responses could be categorized into three kinds. Poplar ′Zhonglin-46′and walnut were included in the first one, P_N of which much decreased immediately on the commencement of salt treatment and decreased more at higher salinity. P_N of velvet ash decreased less than the above two after salt treatment and it could tolerant salt stress about 100 mmol·L^-1 NaCl concentration for at least 14 days. While P_N of pagoda tree increased after salt treatment and it could keep its P_N not less than that of its control at not more than 200 mmol·L^-1 NaCl concentration for at least 24 days. For poplar ′Zhonglin-46′,P_N and leaf total area affected its growth of seedlings under salt stress. For walnut and velvet ash, only the leaf total area was the main reason for the decline of their growth. While P_N and leaf total area could not elucidate the decreased growth of pagoda tree under salt stress.

Key words: Salt stress, Photosynthesis, Growth, Pagoda tree, Velvet ash, Walnut, Poplar &prime, Zhonglin-46&prime