Seed geranium (Pelargonium × hortorum) 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 growing medium were fertilized at each irrigation for 5 weeks with solutions containing 0.25, 0.5, 1, 2, 3, 4, 5, and 6 mm plus the standard concentration of each micronutrient. The standard solution contained 20 μm B, 0.5 μm Cu, 10 μm Fe, 10 μm Mn, 0.5 μm Mo, and 4 μm Zn. All treatment solutions contained a fixed level of macronutrients. Visible foliar toxicity symptoms were produced when the nutrient solution contained 0.5 mm B, 0.5 mm Cu, 5 mm Fe, 1 mm Mn, 0.25 mm Mo, or 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 fertilizer solution. Leaf chlorophyll contents decreased as Cu and Mn levels in the concentration range tested increased. Elevated levels of Fe increased tissue chlorophyll contents. The relationship between the nutrient solution and tissue concentrations of each of the six micronutrients was determined.
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