Aluminium (Al3+) toxicity affects plant root meristem growth and decreases water and nutrient uptake. The aim of this work was to evaluate the effects of Al3+ on the growth of grapia (Apuleia leiocarpa Vog. Macbride) seedling. Under climatized chamber conditions, seedlings were grown for 11d on minirhizotrons in the presence of 0.0, 2.5, 5.0, or 10.0mg L-1 Al3+ in the growth medium, solidified with 7g L-1 agar. At 24h intervals, the absolute and relative elongation rate of the tap root, and the appearance of secondary roots were evaluated; at 7 and 11d of cultivation the rhizosphere pH, plant height, length of the tap root, length of the root system, number and length of the secondary roots, dry weight of roots, dry weight of shoots and of the whole plant, and root/shoot dry weight ratio were analyzed. Seedlings of grapia are tolerant to Al3+ presence in the growth substrate up to 10.0mg L-1. Absolute and relative elongation rate of the tap root of seedlings indicate the existence of an adaptation period of about 48h to high Al3+ (10.0mg L-1). The tolerance of seedlings to Al3+, at concentration of 10.0mg L-1, depends on the increasing of rhizosphere pH.
forest specie; growth; rhizosphere pH; Al3+; minirhizotrom
