INFLUENCE OF ALUMINIUM ON GROWTH, MINERAL NUTRITION AND ORGANIC ACID EXUDATION OF RAMBUTAN (Nephelium lappaceum)

Abstract

SUMMARYA randomized complete block design experiment with six aluminium (Al) concentrations was carried out to evaluate the effect of Al on nutrient content, plant growth, dry matter production and Al-induced organic acid exudation in rambutan (Nephelium lappaceum). One rambutan cultivar was grown in nutrient solution at pH 4.0 with (1.0, 2.3, 4.1, 6.7 and 10.2 mM Al) and without Al. The results of this study confirms that this crop is highly tolerant to Al in the rhizosphere as evidenced by: (1) a root tolerance index (RTI) of 0.85 when plant roots are exposed to Al concentrations as high as 3.5 mM; (2) root tissue Al concentrations as high as 6800 mg g−1and the plants survived; (3) number of leaves, plant height and stem diameter being little affected when plants were grown at an Al concentration in the soil solution as high as 3.5 mM; (4) although plants exhibited leaf abscission, they were able to tolerate Al concentrations in the nutrient solution as high as 10.2 mM during the experimental period. No evidence of organic acid exudation was found in this study. Accumulation of Al in leaves, stems and roots suggests the existence of an Al-sequestration mechanism in rambutan which may involve an Al-ligand complex which translocates from roots to shoots, where it may accumulate in leaf vacuoles.