Physiological responses to salinity in Silver buffaloberry (Shepherdia argentea) introduced to Qinghai high-cold and saline area, China

Abstract

Since 2002, Silver buffaloberry (Shepherdia argentea) has been introduced from North America in order to improve the fragile ecological environment in western China. To elucidate the salt-resistance mechanism of S. argentea, we conducted a test with two-year-old seedlings subjected to 0, 200, 400, and 600 mM NaCl solutions for 30 d. The results showed that significant salt-induced suppression of plant fresh mass (FM) and stem height of S. argentea seedlings occurred only at the highest salinity level (600 mM). Leaf number, plant dry mass (DM), and chlorophyll (Chl) content declined markedly at both 400 and 600 mM. Leaf area (LA) and leaf water potential (Ψw) continuously declined with the increase of salinity. There was also a progressive and evident decrease in net photosynthetic rate (P N), transpiration rate (E), and stomatal conductance (g s) with the increase of salinity and time. The correlation analysis indicated that P N was positively correlated with g s at all salinity levels while correlated with intercellular CO2 concentration (C i) only at moderate salinity levels (<600 mM). Based on the initial slope of the P N/C i curves, the estimated carboxylation efficiency (CE) was strongly inhibited at 600 mM. We confirm that S. argentea is highly tolerant to salinity. Moreover, our results show that at moderate salinity levels, salt-induced inhibition of photosynthesis is mainly attributed to the stomatal efficient closure predetermined by a low water potential in leaves; while at the high salinity levels, the inhibition is mainly due to the suppression of chloroplast capacity to fix CO2 caused by the serious decline in both CE and Chl contents.