Responses of Leaf Ion Content, Photosynthesis and Chlorophyll Fluorescence to Nacl Stress in Soybean

The main purpose of present study was to evaluate the response of leaf ion content, photosynthesis and chlorophyll fluorescence to NaCl stress in soybean (Glycine max L. Men.). During salt treatment, soybean seedlings were exposed to 0 or 200 mM NaCl for 1, 6 or 12 days. The results showed that following treatment with NaCl, the content of Na+ and the Na+/K+ ratio in the leaves continually increased, while the K+ content decreased, which suggested that Na+ could compete with K+ to be adsorbed as an ion. Short-term salt stress may not significantly reduce the ability of soybean to utilize light and CO2, but long-term salinity could obviously impair the photosynthetic capacity in soybean leaves. Moreover, Short-term salt stress may also had no obvious effects on F-q'/F-m' and F-q'/F-v' but severe salt stress would cause the down-regulate of PSII photochemistry and the increase of excessive excitation energy dissipation. The photoinhibitory damage induced by salt stress eventually occured. Consequently, with increased NaCl stress, stem elongation, leaf expansion and biomass accumulation in soybean tended to decrease. These results provided sufficient information on plant photosynthetic response to salinity exposure.