MICRONUTRIENT TOXICITY IN SEED GERANIUM (PELARGONIUM X HORTORUM BAILEY)

Seed geranium (Pelargonium xhortorum) micronutrient toxicity symptoms were induced by applying elevated levels of B, Cu, Fe, Mn, Mo, and Zn in fertilizer solution. Beginning at the 3-4 true leaf stage, seedling plants established in 11-cm (0.67-liter) pots containing peat-lite gr owing medium were fertilized at each irrigation for 5 weeks with solut ions containing 0.25, 0.5, 1, 2, 3, 4, 5, and 6 mh I plus the standard concentration of each micronutrient. The standard solution contained 20 mu M B, 0.5 mu M CU, 10 mu M Fe, 10 mu M Mn, 0.5 mu M MO, and 4 mu M Zn. All treatment solutions contained a fixed level of macronutrient s. Visible foliar toxicity symptoms were produced when the nutrient so lution contained 0.5 raw B, 0.5 mM Cu, 5 mM Fe, 1 mM Mn, 0.25 mM Mo, o r 0.5 mM Zn. Reduction in dry matter yield was evident when 1 mM B, 2 mM Cu, 3 mM Fe, 2 mM Mn, 0.5 mM Mo, or 1 mM Zn was used in the fertili zer solution. Leaf chlorophyll contents decreased as Cu and Mn levels in the concentration range tested increased. Elevated levels of Fe inc reased tissue chlorophyll contents. The relationship between the nutri ent solution and tissue concentrations of each of the six micronutrien ts was determined.