Significant improvement of salt tolerance with 2-day acclimatization treatment in Elaeagnus oxycarpa seedlings

To enhance the salt tolerance of Elaeagnus oxycarpa, an orchard tree widely used for revegetation in northwest China, we applied a stress acclimatization treatment to hydroponically grown seedlings for 2 days by adding polyethylene glycol (PEG) to the culture solution. The seedlings were then transferred to culture solution containing 300mM NaCl for 2 weeks to evaluate their salt tolerance. All seedlings pretreated with 20% (w/v) PEG survived until the end of the NaCl treatment, while most seedlings without the acclimatization treatment died. The photosynthetic rate and chlorophyll fluorescence of the un-pretreated seedlings were dramatically decreased by salt stress; however, photosynthesis was maintained and chlorophyll fluorescence was almost unchanged in the seedlings subjected to acclimatization pretreatment with 20% PEG. The acclimatization treatment significantly increased fructose, glucose, and Ca ²⁺, and slightly increased maltose, K ⁺, Mg ²⁺, and β-alanine betaine in leaves. We conclude that 2-day stress acclimatization treatment can improve salt tolerance of E. oxycarpa seedlings enough to adapt them to a lethal concentration of NaCl.