Amelioration of manganese toxicity in barley with iron

The ameliorating effect of additional iron (Fe) on manganese (Mn) toxicity in barley (Hordeum vulgare L. cv. Minorimugi) was evaluated using 1/2-strength modified Hoagland-Amon nutrient solution. Manganese toxicity (2.50 muM Mn) was expressed as reduced dry matter yield, redistribution of growth, mild inter-veinal chlorosis on younger leaves, brown spots on older leaves and stems, phytosiderophore (PS) release from roots, and gradual desiccation of older leaves and root browning. The PS released from roots of plants was identified, using high-performance liquid chromatography (HPLC), as mugineic acid. Application of additional Fe (100 muM) to Mn stressed plants fully counteracted Mn-induced Fe deficiency symptoms, recovered total dry matter yield partially, and changed the plant's composition and accumulation of essential mineral nutrients. The Mn critical toxicity levels in shoots and roots of Mn stressed plants with 10.0 muM Fe, expressed by reduced growth, were 44 and 147 mug g(-1) dry matter, respectively. The Mn concentrations in shoots and roots of Mn stressed plants with 100 muM Fe were reduced significantly although still above critical toxicity levels, indicating that elevation of Fe could ameliorate Mn toxicity to some extent.