RESPONSE OF IRON-DEFICIENT BARLEY PLANTS TO MANGANESE IN NUTRIENT SOLUTION

Abstract

Barley (Hordeum vulgare L. cv. Minorimugi) plants were cultured in iron (Fe)-deficient nutrient solutions at three levels (0.25, 0.025, and 0.0025 μM) of manganese (Mn). Iron-deficient plants with high Mn (0.25 μM) had brown spots on older leaves and stems characteristic of Mn toxicity. In the nutrient solution at 0.0025 μM Mn, the younger leaves had typical symptoms of Mn deficiency. Iron-deficient plants with 0.025 μM Mn had shoot Mn concentration statistically similar to Fe-sufficient plants with 0.25 μM Mn. Tissue Fe and Mn concentrations were reciprocally related in shoots and roots of plants grown in 0.25 μM Mn with and without Fe. The Mn concentration of Fe-deficient plants decreased with decreasing Mn concentrations in the nutrient solution. In contrast, the Mn levels in the nutrient solution did not significantly affect the Fe concentrations of Fe-deficient plants with identical Fe deficiency symptoms. The highest level of phytosiderophore (PS) released from roots of Fe-deficient plants occurred with 0.025 μM Mn and the least with 0.0025 μM Mn. A deficiency of Fe decreased the translocation of Fe and Cu from roots to shoots, but had little or no effect on the translocation of Mn and Zn.

ACKNOWLEDGMENTS

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