Please cite this article in press as: Barbosa, R.M.T. et al., A physiological analysis of Genipa americana L.: A potential phytoremediator tree for chromium polluted watersheds, Environmental and Experimental Botany (2007), doi:10.1016/j.envexpbot.2007.06.001 ARTICLE IN PRESS +Model EEB-1768; No. of Pages 8 Environmental and Experimental Botany xxx (2007) xxx–xxx A physiological analysis of Genipa americana L.: A potential phytoremediator tree for chromium polluted watersheds Rena M´ ırian T. Barbosa, Alex-Alan F. de Almeida ∗ , Marcelo S. Mielke, Leandro L. Loguercio, Pedro A.O. Mangabeira, F´ abio P. Gomes Departamento de Ciˆ encias Biol ´ ogicas, Universidade Estadual de Santa Cruz, Rod. BR 415, km 16, 45662-000 Ilh´ eus, BA, Brazil Received 16 May 2007; accepted 8 June 2007 Abstract 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 Cr 3+ -contaminated watersheds. In this way, approximately 2-month-old seedlings were subjected to increased concentrations of Cr 3+ 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 belowground components of plant dry mass. The seedlings were submitted to seven increasing concentrations of Cr 3+ in nutrient solution. At 34 days, leaf gas exchange parameters in the maximal tested dose of Cr 3+ (30 mg L -1 ) remained below the control; the 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 Cr 3+ 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 Cr 3+ 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 Cr 3+ in the nutrient solution. On the other hand, Fe and K contents presented a negative proportional increment to the increase of the concentration of Cr 3+ . There was little effect of Cr 3+ 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 Cr 3+ 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 Cr 3+ . © 2007 Elsevier B.V. All rights reserved. Keywords: Chemical composition; Heavy metal; Leaf gas exchange; Rhizofiltration; Rubiaceae 1. Introduction In the last decades, the amount of chromium in aquatic and terrestrial ecosystems has increased as result of different anthropogenic human activities (Kleiman and Cogliatti, 1998). In plants, Cr 3+ has been reported to affected the net photosyn- thesis (Bishnoi et al., 1993), lowered the biomass weight and decreasing the concentrations of most nutrients such as Cu, Mg, Mn, Fe, P and K (Turner and Rust, 1971). Furthermore, toxic concentrations of Cr 3+ usually promote chlorosis and necrosis of leaves (Barcel´ o et al., 1986), as a consequence of photosynthe- sis inhibition (Sarkar and Jana, 1987) and disturbance in mineral ∗ Corresponding author. Tel.: +55 73 3680 5105; fax: +55 73 3680 5226. E-mail address: alexalan@uesc.br (A.-A.F. de Almeida). nutrition, which will, eventually, promote decrease in the rates of plant growth (Otabbong, 1989). Terrestrial plants with great biomass production (Shanker et al., 2005), tolerant to flooding, and capable of developing an extensive root system commonly have a great capacity to extract heavy metals from the soil. In this way, they can be used for decontamination of watersheds, recomposition of gallery forests and removal of heavy metals from the water (Kleiman and Cogliatti, 1998). The use of plants for either the removal of organic or inorganic pollutant substances, such as hydrocar- bons of petroleum, chemical residues in agriculture, explosives, chlorinated solvents, toxic by-products of the industry and heavy metals from the environment, or their rendering into harmless levels, is defined as ‘phytoremediation’ (Salt et al., 1998). The development of this method has been driven primarily by the high costs of many other soil remediation methods, as well as 0098-8472/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2007.06.001