Determination of physiological indices
The MDA (malondialdehyde) content in leaves of Arabidopsis plants were performed as described previously (Breuil & Saddler, 1985; Shabala, Shabala, Martynenko, Babourina, & Newman, 1998; Sofo, Dichio, Xiloyannis, & Masia, 2004). Relative electrolyte leakage (%) in leaves of Arabidopsis plants was determined according to the (Dionisio-Sese & Tobita, 1998) method. The total phosphorus content was determined by using Total Phosphorus Assay Kit (Yoyobio, Shanghai, China). The inorganic phosphorus content was determined by using Inorganic Phosphorus Assay Kit. The content of starch and soluble sugar were determined by using Starch Kit and Soluble Sugar Kit. The enzyme activities of amylases, SOD, POD and CAT were determined by using Amylases Kit, SOD Kit, POD Kit and CAT Kit. All of the above unmarked Kits are produced from Comin (Suzhou, China).