Transport and distribution of manganese in two cultivars of soybean (Glycine max (L.) Merr.)

Abstract

Transport and distribution patterns of manganese were studied in soybeans (cultivars Lee and Bragg) grown over a wide range of manganese supply levels in solution culture. Increasing the manganese supply from 1.8 ¦M to 450 .¦M produced symptoms of manganese toxicity and reduced growth in both cultivars. Symptoms and dry matter yield reductions were more severe in Bragg. Manganese taken up by the plant was preferentially transported to young expanding tissue, while the amount moving to older tissue, including cotyledons, increased with availability. At high manganese supply the leaves accumulated higher concentrations with age, resulting in a decreasing concentration gradient between old and young leaves. There was no difference between Lee and Bragg in the distribution of manganese to plant parts or in the concentration of manganese in actively growing tissue. Manganese deficiency symptoms developed on both cultivars grown under limiting supply conditions. Partial mobility of the element was indicated: small amounts were translocated from the old leaves when young expanding leaves were manganese deficient. Nevertheless, considerable amounts remained in the cotyledons, and manganese appeared to have a low mobility when the plant's supply was limited.