Manganese Deficiency and Toxicity Effects on Growth, Development, and Nutrient Composition in Wheat1

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Abstract
Wheat (Triticum aestivumL.) production areas have expanded to soils low in available Mn and to low pH soils with excess available Mn. The purpose of this study was to determine the effect of Mn deficiency and toxicity effects on ‘Stacy’ wheat growth components and to determine the Mn critical deficiency level (CDL) and critical toxicity level (CTL) in specific plant tissue in relation to top dry weight. The critical deficiency and toxicity values could be used as guidelines in tissue analysis to diagnose Mn deficiency and toxicity. Wheat plants were grown in nutrient solution containing 10 Mn rates from 0.09 μMto 9.1 mMin the greenhouse. Plants were harvested 26 days following treatment with Mn and tissue samples were analyzed for Mn and other elements in the wet ashed extract. Manganese deficiency and toxicity reduced top dry weight, root dry weight, plant height, and tiller number compared with plants supplied at adequate Mn levels. The CDL and CTL defined as the elemental concentration in the tissue associated with a 10% reduction in growth due to a deficiency or toxicity, respectively, were determined from the relationship of Mn concentrations in the tissue and top dry weight. The Mn CDL values for blades 1, 2, 3, and stem of Stacy wheat were 13,39,82, and 12 μg g‐1, respectively. Blade 1 is recommended for tissue sampling since the transition zone in the response curve is narrow and blade 1 is metabolically active and the most recently matured blade with a developed ligule. The Mn CTL values of the sampled tissues were 380, 900, 1100, and 200 μg g‐1for blades 1, 2, 3, and stem tissue, respectively. Maximum growth would be expected when tissue Mn concentrations are within the CDL and CTL of a specific plant tissue. The Mn concentration in tissues increased as Mn supply was increased. A reciprocal Fe/Mn and P/Mn concentrations existed in blade 1. Manganese deficiency and toxicity reduced K, Ca, and Mg concentrations.