AMELIORATION OF MANGANESE TOXICITY IN BARLEY WITH IRON

Abstract

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-Arnon nutrient solution. Manganese toxicity (2.50 μM Mn) was expressed as reduced dry matter yield, redistribution of growth, mild interveinal 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 μM) 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 μM Fe, expressed by reduced growth, were 44 and 147 μg g^{− 1} dry matter, respectively. The Mn concentrations in shoots and roots of Mn stressed plants with 100 μM Fe were reduced significantly although still above critical toxicity levels, indicating that elevation of Fe could ameliorate Mn toxicity to some extent.

ACKNOWLEDGMENTS

This research is part of an ongoing project on the Mechanism of Mineral Uptake and Transformation in Plants conducted at Iwate University. The authors wish to thank the Ministry of Education, Science, and Culture, the Government of Japan for financial support, Dr. S. Saiga of Iwate University for statistical analysis, and Mr. S. Satoh for computer assistance. The authors are grateful to Dr. D.M. Huber, Professor of Purdue University, for review of the manuscript and helpful suggestions.