Callose formation as parameter for assessing genotypical plant tolerance of aluminium and manganese

Abstract

Callose ((1,3)-β-glucan) formation in plant tissues is induced by excess Al and Mn. In the present study callose was spectrophotometrically quantified in order to evaluate whether it could be used as a parameter to identify genotypical differences in Al and Mn tolerance. Mn leaf-tissue tolerance of cowpea and linseed genotypes was assessed using the technique of isolated leaf tissue floating on Mn solution. Genotypical differences in the density of brown speckles on the leaf tissue (Mn toxicity symptoms) correlated closely with the concentrations of callose for both plant species. In cell suspension cultures Mn excess also induced callose formation. However, differences in tolerance of cowpea genotypes using callose formation as a parameter could only be found in cultured cowpea cells if controls cultured at optimum Mn supply showed low background callose. As soon as after 1 h, Al supply (50 µ M) induced callose formation predominantly in the 5-mm root tip of soybean seedlings. Callose concentration in the 0-30 mm root tips was inversely related to the root elongation rate when roots were subjected to an increasing Al supply above 10 µ M. Three soybean genotypes differed in inhibition of root-elongation rate and induction of callose formation when treated with 50 µ M Al for 8 h. Relative callose concentrations and relative root-elongation rates for these genotypes were significantly negatively correlated.