Manganese Deficiency and Toxicity in Wheat: Influence on Growth and Forage Quality of Herbage1

Abstract

AbstractThere is little information concerning critical Mn deficiency and toxicity levels in forage plants, or how plant Mn concentration affects other plant constituents associated with forage quality. This study was undertaken to investigate possible interactions between plant Mn concentration and the growth and forage quality of wheat (Triticum aestivum L. cv. Stacy).Wheat plants were grown in nutrient solution containing 0.005, 0.02, 0.05, 0.25, 1, 5, 25, 100, 200, and 500 µg/g Mn. Plants were grown for 30 days after transplanting into nutrient solution and were harvested at the three‐leaf stage, lyophilized, and weighed. Manganese concentration, in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), in vitro cell wall disappearance (IVCWD), total nonstructural carbohydrates (TNC), and Ca and Mg concentrations were determined on wheat shoot.Critical Mn deficiency and toxicity levels affecting normal growth of wheat shoot were determined to be 35 and 475 µg/g dry wt, respectively. These values are useful in determining deficiency and toxicity in wheat production. Percentage NDF, IVDMD, TNC, and IVCWD were reduced in tissue from plants that were critically Mn‐deficient. In vitro dry matter disappearance and TNC were increased in tissue from critically Mn‐toxic plants.In vitro dry matter disappearance ranged from 71 to 89%, with the lowest values observed for Mn‐deficient and the highest for Mn‐toxic plants. The high IVDMD of the Mn‐toxic plants appeared to be related to an accumulation of TNC, while the relatively lower IVDMD of the Mn‐deficient plants was related to reduced cell wall digestibility. Both Ca and Mg concentrations decreased as Mn concentration in the plants increased above 475 µg/g.Results of this study indicate that Mn deficiency and toxicity in wheat have a significant effect on amount of growth and the concentration of plant constituents associated with forage quality. These constituents remain relatively constant over the adequate range of Mn nutrition and plant Mn concentration should be kept within the 35 and 475 µg/g range.