Excess trace metal effects on cotton. 1. Copper, zinc, cobalt and manganese in solution culture

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Abstract
Two cultivars of cotton (Gossypium spp) were grown in solution culture in a glasshouse to determine phytotoxicity effects of excesses of Cu, Zn, Co and Mn. Leaf yields of Acala SJ‐2 were depressed 76% by 10‐4 M CuSO4, 86% by 5×10‐4 M ZnSO4, 82% by 10‐4 M CoSO4, and 20% by 10‐3 M MnSO4. Leaf concentrations associated with these depressions were (μg/g) 110 Cu, 198 Zn, 180 Co, and 5470 Mn respectively. Plants were tolerant of in μg/g of about 15 Cu, 106 Zn, 69 Co, and 1830 Mn. Leaf yields of Giza 70 were depressed 91% by 10‐4 M CuSO4, 88% by 5×10‐4 M ZnSO4, 87% by 10‐4 M CoSO4, and 68% by 10‐3 M MnSO4. This cv. was less tolerant of Mn than was Acala SJ‐2. Leaf metal concentrations at these application rates were (μg/g) 65 Cu, 243 Zn, 255 Co, and 6550 Mn respectively. In general roots were higher in these four metals than stems and leaves. There was no strong gradient from stems to leaves. Many nutrient interactions were observed as result of excesses of the four trace metals.