Boron-calcium synergically alleviates aluminum toxicity in wheat plants (Triticum aestivum L.)

The effects of B and Ca treatments on root growth, nutrient localization and cell wall properties in wheat (Triticum aestivum L.) plants with and without Al stress were investigated. Seedlings were grown hydroponically in a complete nutrient solution for 7 d and then treated with B (0, 40 MicroM), Ca (0, 2,500 MicroM), and Al (0, 100 MicroM) in a 500 MicroM CaCl sub(2) solution for 8 d. The cell wall materials (CWM) were extracted with a phenol: acetic acid: water (2: 1: 1 w/v/v) solution and used for subsequent pectin extraction with trans-1,2-diami-nocyclohexane-N,N,N,N-tetraacetic acid (CDTA) and Na2CO3 solutions. Boron, Ca, and B+Ca treatments enhanced root growth by 19.5, 15.2, and 27.2%, respectively, compared to the control (pH 4.5). Calcium and B + Ca treatments enhanced root growth with Al stress by 43 and 54%, respectively, while B did not exert any effect. The amounts of CWM and pectin per unit of root fresh weight increased by Al treatment, Whereas the Ca and B+Ca treatments slightly reduced the contents of these components, Seventy-four percent of total B, 69% of total Ca, and 85% of total Al were located in the cell wall in the B, Ca, and Al treatments, respectively and 32% of total B, 33% of total Ca, and 33% of total Al were located in the CDTA-soluble and Na2CO3-soluble pectin fractions. A more conspicuous localization of B was observed in the presence of Al. Aluminum treatment markedly decreased the Ca content in the cell wall as well as pectin fractions, mainly in the case of the CDTA-soluble pectin fraction. Boron + Ca treatment decreased the Al content In the cell wall and pectin fractions compared to the Ca treatment alone in the presence of Al. It is concluded that the B +Ca treatment enhanced root growth and, B and Ca uptake, and helped to maintain a normal B and Ca metabolism in the cell walls even in the presence of Al.