Aluminum Stress Effects of Nine Tropical Tree Species In The Hydroponic Assay

Aluminum (Al) toxicity usually occurs in acidic soils with a pH of 5.5 or lower. Plants present different degrees of adaptation to al concentrations in the soil. Recent evidence indicates that different species have evolved different mechanisms to cope with this stress, and the understanding of this characteristic can lead to a viable option for the utilization of acid soils. The objective of this experiment was to investigate the effect of nine level Al concentration on nine tropical trees seedling ( Enterolobium cyclocarpum Griseb, Adenanthera pavonina L. Samanea saman (Jacq.), Spathodea campanulata P.Beauv Merr, Ochroma grandiflora Rowlee, Gmelina arborea Roxb, Calophyllum inophyllum, Cecropia peltata, and Calliandra calothyrsus) in the hydroponic culture. The treatments arranged in a Randomized Block Design with three replications. The relative root elongation and roots number in terms of increased under low (below 2 mM) and, decreased under high (above 4 mM) Al concentrations. Significant reductions in relative root elongation, lateral root number and biomass observed almost in all seedling treated with hight Al concentration. A. pavonina , E. cyclocarpum , C. inophyllum classify into tolerance and S. campanulata were the most susceptible to Al. Even though A. pavonina was tolerant to Al toxicity, there was a high concentration in its tissue. This species is likely has an Al tolerance mechanism by internal detoxication. On the contrary, S.saman as sensitive species absorbed Al less than other species; it indicated that S.saman was have an avoidance mechanism as Al exclusion.