In this study, the seedlings of wheat were treated with salt stress (molar ratio of NaCl:Na2SO4 = 1:1) and alkali stress (NaHCO3:Na2CO3 = 1:1). The contents of organic acids and inorganic ions in the seedlings then were measured, and the organic acids in root secretions also were analyzed to probe the roles of organic acids in wheat alkali tolerance. The results showed that the content of Na+ increased greatly, whereas the contents of NO3–, SO42- and H2PO4– decreased significantly. This caused a severe deficit of negative charge. The deficit of negative charge was remedied by greatly accumulated organic acids (OAs), with malic and citric acids as the dominant components in shoots. Therefore, the accumulation of OAs might result from the deficit of negative charge, and OA metabolic regulation might be a key pathway for keeping ionic balance and stable the pH. Secretion of OAs such as lactic, acetic and formic acids was significantly stimulated by alkali stress, indicating that OA secretion may be important in pH adjustment outside roots.
Key words: Wheat, salt stress, alkali stress, organic acid, secretion, pH adjustment.
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