ALUMINUM TOXICITY IN TOMATO .1. GROWTH AND MINERAL-NUTRITION

Aluminum (Al) toxicity was studied in two tomato cultivars (Lycopersicon esculentum Mill. 'Mountain Pride' and 'Floramerica') grown in diluted nutrient solution (pH 4.0) at 0, 10, 25, and 50 mu M Al levels. In the presence of 25 and 50 mu M Al, significant reduction was found in leaf area, dry weight, stem length, and longest root length of both cultivars. Growth of 'Floramerica' was less sensitive to Al toxicity than growth of 'Mountain Pride'. Elemental composition of the nutrient solutions were compared immediately after the first Al addition and four days later. The uptake of micronutrients copper (Cu), manganese (Mn), molybdenum (Mo), zinc (Zn), boron (B), and iron (Fe) from the nutrient solution was reduced in both cultivars with increasing Al levels. Nutrient solution Al gradually decreased in time for every treatment; less in cultures of 'Floramerica' than in 'Mountain Pride'. Aluminum treatments decreased the calcium (Ca), potassium (K), magnesium (Mg), Mn, Fe, and Zn content in the roots, stems, and leaves. Aluminum treatment promoted the accumulation of P, Mo, and Cu in the roots, and inhibited the transport of these nutrients into stems and leaves. At 25 and 50 mu M levels of Al, lower Al content was found in the roots of cv. 'Floramerica' than in the roots of cv. 'Mountain Pride'.