Abstract:
The growth, gas exchange parameters and chlorophyll fluorescence parameters were investigated in Nitraria sibirica under the soda salinealkaline stress in pots. The results showed that moderate soda salinealkaline contents in soil could stimulate biomass and growth of N. sibirica. At a level of 0.2% soda salinealkaline content in soil, the biomass peaked, 27.3%higher than that of the control. Under high levels of soda salinealkaline stress, the net photosynthetic rate declined, mainly due to nonstomatal limitation factors and partially due to the decrease in leaf water content and chlorophyll content. The increase of intercellular CO2 concentration under high levels of soda salinealkaline stress might result partially from the nonuniform stomatal closure. The content of carotenoid dropped at a low level of soda salinealkaline content in soil but lifted at higher levels, while NPQ showed no significant differences under various levels of soda salinealkaline stress. It is suggested that a high level of NPQ in N. sibirica could be kept by increasing the content of carotenoid. There were significantly positive correlations between biomass and Pn, LUE, CUE, stomatal limitation value (Ls), Fv/F0, Fv/Fm (P0.01). The primary indices that could be used to evaluate the tolerance of N. sibirica to soda salinealkaline stress are biomass, Pn, LUE, CUE, Fv/F0 and Fv/Fm, while the secondary ones include Ls and Fm. The effectiveness of the indices depends on the type of salts in soil.