Effect of Magnesium and Manganese Nutrition on Watermelon Growth and Manganese Toxicity

Abstract

Abstract Watermelon [ Citrullus lanatus (Thunb.) ‘Sugar Baby’ was grown in sand culture to evaluate Mn uptake as affected by solution concentration of Mn and Mg. Manganese toxicity symptoms were developed first on the lower mature leaves as small, distinct, blackish-brown speckling on the lower leaf surface that progressed to extensive vein browning and necrotic lesions. Leaves developed toxicity symptoms when they contained ≥1325 mg·liter −1 Mn. Growth was reduced at Mn concentrations in nutrient solution ≥22.5 mg·liter −1 . Development of Mn toxicity symptoms was delayed with increasing Mg concentrations in solutions. Increasing Mg concentration in solution to 48 or 96 mg·liter -1 reduced Mn composition and Mg uptake per unit root surface at 2 and 30 mg·liter -1 Mn in solution, but had no effect at 60 mg·liter -1 Mn in solution.