INFLUENCE OF [Al.sup.3+] IN NUTRIENT SOLUTION ON GROWTH OF THREE FOREST SPECIES USED IN RECOVERY OF DEGRADED AREAS/INFLUENCIA DO [Al.sup.3+] EM SOLUCAO NUTRITIVA NO CRESCIMENTO DE TRES ESPECIES FLORESTAIS UTILIZADAS NA RECUPERACAO DE AREAS DEGRADADAS

One of the main limiting factors in the performance of agricultural and forest crops in tropical soils is the toxic effect of [Al.sup.3+] in soils. However, some plant species present adaptive mechanisms that confer tolerance to these conditions. The aim of this study was to evaluate the development of three tree species grown in nutrient solution with different levels of [Al.sup.3+]. Therefore, seedlings of Acacia mangium, Mimosa artemisiana and Enterolobium contortisiliquum were produced in nutrient solution with four concentrations of [Al.sup.3+] (control, 185, 370 and 555 [micro]mol [L.sup.-1]) during 95 days of cultivation. At the end of the experiment, the plants were targeted and a fraction of the known roots was scanned to estimate root area and length. The stem, leaves and remaining roots were dried in a forced air oven, being determined the biomass and N, P and K in plant tissue. The species showed different patterns of growth due to the increase of the activity of [Al.sup.3+] in nutrient solution, and Acacia mangium and Enterolobium contortisiliquum were more tolerant to [Al.sup.3+], demonstrating potential use in the recovery of degraded areas with acid soils. The N concentration in the plant parts were not influenced by [Al.sup.3+], however the concentration of P increased in the roots of three species with intermediate levels of [Al.sup.3+], resulting in reduction of P in shoots of Acacia mangium and Mimosa artemisiana. The concentration of [K.sup.+] in Acacia mangium was reduced only in the lower [Al.sup.3+], whereas for Mimosa artemisiana was gradually reduced. Keywords: Forest nutrition; Mimosa artemisiana; Enterolobium contortisiliquum; Acacia mangium. Um dos principais fatores limitantes no desempenho das culturas agricolas e florestais na maioria dos solos tropicais e o efeito toxico do [Al.sup.3+]. No entanto, algumas especies vegetais apresentam mecanismos de adaptacao que lhes conferem tolerancia a essas condicoes. O objetivo deste estudo foi avaliar o desenvolvimento de tres especies florestais cultivadas em solucao nutritiva com diferentes niveis de [Al.sup.3+]. Para tanto, mudas de Acacia mangium, Mimosa artemisiana e Enterolobium contortisiliquum foram cultivadas em solucao nutritiva com quatro concentracoes de [Al.sup.3+] (controle, 185, 370 e 555 [micro]mol [L.sup.-1]) durante 95 dias. Ao final do experimento, as plantas foram segmentadas e uma fracao conhecida das raizes foi digitalizada para estimativa de area e comprimento r