Mechanism of Potassium Alleviation of Manganese Phytotoxicity in Barley

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Abstract
Manganese (Mn) toxicity and potassium (K) deficiency are the major factors that limit plant growth and development in acid soils. The objective of this study was to assess the role of high K on the alleviation of Mn toxicity in barley (Hordeum vulgare L. cv. ‘Minorimugi’) grown in a phytotron for 14 d. Modified half-strength Hoagland-Arnon solution (pH 5.5) was used as the medium. The treatments were (1) 0.25 μ M Mn + 3 mM K (control); (2) 25 μ M Mn + 3 mM K (Mn-toxic); and (3) 25 μ M Mn + 30 mM K (K-alleviated). The Mn-toxic plants showed the symptoms of Mn toxicity and mild iron (Fe) deficiency, whereas in the K-alleviated plants such symptoms were absent. The K-alleviated plants had dry weight, chlorophyll content, and Fe concentration similar to that in the control plants, indicating that high K (30 mM) in the growth medium could alleviate Mn toxicity and Mn-induced Fe deficiency. Roots of plants fed separately with 54Mn and 59Fe in the presence of 3.0 and 30 mM K for 4 h were also studied. R...

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