A physiological analysis of Genipa americana L.:: A potential phytoremediator tree for chromium polluted watersheds

Chromium is a highly toxic heavy metal for microorganisms. animals and plants. Due to its widespread industrial use, it has become a serious pollutant in a diverse array of environments. Genipa americana L. (Rubiaceae) is a neotropical wood plant that shows adaptive capabilities to adverse conditions. such as soil flooding. We conducted an experiment under greenhouse conditions in order to test the hypothesis that G. americana can be used as a phytoremediator tree in Cr3+ -contaminated watersheds. In this way, approximately 2-month-old seedlings were subjected to increased concentrations of Cr3+ in nutritive solution to analyse the effects of the metal on the leaf gas exchange, growth, carbon allocation and mineral composition in the above and below-round components of plant dry mass. The seedlings were submitted to seven increasing concentrations of (30 mg L-1) remained below the control; the Cr3+ in nutrient solution. At 34 days, leaf gas exchange parameters in the maximal tested dose of Cr3+ net values of photosynthetic rate (A) and stomatal conductance to water vapor (gs) were lowered approximately 80 and 90%, respectively. There were decreases of 36% in total leaf area (LA) between 0 and 30 mg L-1 Cr3+ and reductions in the roots, stems, leaves and total biomasses of 29, 39, 30 and 31%, respectively. The largest values of A to gs ratios were obtained for controls. The Cr3+ accumulated preferentially in the roots and low levels of its transport to the aerial parts was detected. Notwithstanding, Cu and Na concentrations in the seedlings increased with increment of Cr3+ in the nutrient solution. On the other hand, Fe and K contents presented a negative proportional increment to the increase of the concentration of Cr3+. There was little effect of Cr3+ on the contents of Mn. N and P in the seedlings. Despite some stress symptoms (root-apex necrosis, leaf chlorosis. and decreases in A and gs, growth and absorption of some mineral elements), the G. americana seedlings showed a great amount of Cr3+ uptake from the solution. immobilizing and storing it in high concentrations in the roots. Therefore, this woody species presents a great potential as a phytoremediator. mainly as a rhizofilterer and phytostabilizer of Cr3+. (C) 2007 Elsevier B.V. All rights reserved.