Effect of calcium on the alleviation of boron toxicity and localization of boron and calcium in cell wall of wheat

Abstract

A greenhouse experiment involving four levels of B (0, 5, 10 and 20 mg B kg-1 as boric acid, H3BO3), and three levels of Ca (0, 100 and 200 mg Ca kg-1 calcium chloride, CaCl2) were conducted on wheat plants (Triticum aestivum L. 'Gerek-79'). Boron toxicity symptoms strongly occurred at 10 and 20 mg B kg-1 levels with and without applied Ca. Without applied calcium, boron toxicity symptoms were also weakly expressed at 5 mg B kg-1 level. Growing wheat plants with application of high levels of Ca partially alleviated the toxicity symptoms. Shoot and root dry weight of plant was strongly depressed and decreased by applied boron; however, Ca applications reduced the inhibitory effect of B on the plant growth. Shoot and root boron concentrations and boron uptake were increased with increasing B application, but decreased with Ca applications. Controversially, applied calcium increased calcium concentrations and uptake and decreased boron concentrations and uptake. Most of total boron and calcium were localized in the cell wall of plant. While applied boron increased the concentration of B on the cell wall, it decreased the concentration of Ca on the cell wall. In addition, applied calcium increased the cell wall calcium concentration, whereas decreased the cell wall boron concentration. It was determined that boron toxicity could be alleviated by addition of calcium in plant growing media.