IRON AND MANGANESE ACCUMULATION BY THE BRZ PEA MUTANT GROWN IN SOILS

Leaf composition of the bronze (brz) mutant pea [Pisum sativum L. cv. Sparkle E107 (brz brz)] and its parent genotype (cv. Sparkle) have been compared when grown in nutrient culture, but not when grown in soil where pH has been adjusted to reduce readily available Fe and Mn. Both genotypes were grown in a growth chamber in five soils that differed in pH and DTPA-extractable Fe and Mn. The brz genotype accumulated very high, and often toxic, concentrations of Fe and Mn when grown in acidic soils, while Sparkle did not. Liming reduced leaf-Fe and leaf-Mn concentrations in the bn mutant, but Fe toxicity symptoms were still evident in older leaves. In the acidic soils, leaves of the bn plants also accumulated significantly more Zn, Cu, Ca, Mg, K, Na, Al, and P than did leaves of Sparkle plants. Roots of the brz genotype depressed soil pH by several tenths of a pH unit more than did roots of Sparkle. In contrast to results obtained in the acidic and near-neutral soils, the brz mutant and its parent grew similarly in a calcareous soil (pH 8.2), which contained low concentrations of DTPA-extractable Fe and Mn. In conclusion, the brz mutant pea consistently accumulates high levels of Fe and Mn when these metal ions are present in readily available forms. Liming an acid soil to near-neutral pH did not prohibit the bn mutant from accumulating potentially toxic concentrations of Fe, but growing the mutant in a calcareous soil did.