Effects of aluminum, nitrate and ammonium on the metabolic nitrogened composition and of carboidrates in Stylosanthes guianensis and S-macrocephala

The effects of aluminum, nitrate and ammonium interaction, in nutritive sol ution, on the concentration of nitrogened compound, and of sugar in Stylosa nthes guianensis and S. macrocephala, sensitive and tolerant, respectively, both to aluminum and to ammonium were studied under controlled conditions. The ammonium nutrition caused the appearance of toxicity symptoms of ammon ium only in the S. guianensis. The ammonium source increased the concentrat ions of N-soluble, N-ammonium and N-amino acid mainly in the aerial part of the S. guianensis and in the root system of the S. macrocephala, while the total soluble sugar concentration increased in the aerial part of the S. g uianensis and decreased in the root system of both species. The aluminum re lieved partially the ammonium toxicity in the S. guianensis. When the nitro gen was supplied by the nitric source, the addition of the aluminum to the nutritive solution caused the appearance of symptoms of toxicity only in th e S. guianensis. In the S. macrocephala, under the same conditions, an incr ease of total N, insoluble N, soluble N, nitric N and amino acid N in the a erial part and in the roots occurred, followed by a decrease in the total s oluble sugar concentration and sugar reductor in the roots.