SOIL EXCHANGEABLE ALUMINUM INFLUENCING THE GROWTH AND LEAF TISSUE MACRONUTRIENTS CONTENT OF CASTOR PLANTS

Three castor (Ricinus communis) genotypes were studied regarding tolerance to high exchangeable aluminum in the soil and the changes in macronutrient content in leaf tissue. The treatments consisted of a factorial distribution of five doses of exchangeable aluminum added to the soil (0, 0.15, 0.30, 0.60, and 1.20 cmolc dm-3) and three castor genotypes (BRS Nordestina, BRS Paraguacu, and Lyra). The plants were raised in pots in a greenhouse. At 53 days after emergence, data were taken on plant height, leaf area, dry mass of shoot and root, and leaf tissue content of macronutrients. The most sensitive genotype was the cv. BRS Nordestina, in which the shoot and root dry weight in the highest aluminum content were reduced to 12.9% and 16.2% of the control treatment, respectively. The most tolerant genotype was the hybrid Lyra, in which the shoot and root dry weight in the maximum content of aluminum were reduced to 43.5% and 42.7% of the control treatment, respectively.The increased exchangeable aluminum affected the leaf nutrient content, and the intensity of the response was different among cultivars. The aluminum toxicity increased N, Ca, and Mg contents and reduced on P, K, and S contents. The cv. BRS Nordestina had a drastic shoot dry weight reduction associated with an intense increment in the N leaf content. Thus, the N increment was caused by a concentration effect caused by the limited growth.