Star fruit (Averrhoa carambola) plants tend to accumulate significant amounts of Mn in their tissues. However, information regarding the form in which the plant stores the excess is scarce. For a deeper understanding of this aspect, star fruit plantlets were grown in nutritive solutions of Furlani (1999) with increasing levels of Mn (0, 0.5, 25 and 50 mg L-1), and after 30, 60, 90 and 120 days the tissues were collected and subjected to a sequence of extracting solutions: water, DTPA (diethyltriaminepentacetic acid), and HCl (chloridric acid) 1 mol L-1. Then, Mn was determined in the extracts and remaining tissues. Increasing Mn concentrations were found in the extracts with water, DTPA and HCl. The greatest part of Mn (about 50 %) was detected in the remaining tissues, even after successive extractions with the different solutions, suggesting a strong linkage to plant tissues. Highest Mn concentrations were found in the roots, then the stalk and the leaf tissues, suggesting that star fruit plants tend to fix Mn in the root tissues, which is possibly a defense mechanism to limit Mn transport to the aerial part, to avoid plant intoxication.
Averrhoa carambola; star fruit; tolerance; micronutrients; manganese
