J. Plant Physiol. 160. 1447 – 1450 (2003)  Urban & Fischer Verlag http://www.urbanfischer.de/journals/jpp Study of aluminum toxicity by means of vital staining profiles in four cultivars of Phaseolus vulgaris L. Benet Gunsé, Teresa Garzón, Juan Barceló* Laboratorio Fisiología Vegetal, Facultad de Ciencias, Universidad Autónoma de Barcelona, E-08193 Bellaterra (Cerdanyola del Vallès), Spain Received December 5, 2002 · Accepted February 1, 2003 Summary Aluminum toxicity is a very important factor limiting crop productivity on acid soils. Early effects of aluminum toxicity comprise inhibition of cell division and effects on root elongation. The plasma mem- brane can be the primary target of aluminum toxicity and thus, vital staining techniques could be a powerful tool in determining effects of metal stress on the plasma membrane. In this paper, we discuss the effects of Al on growth and membrane integrity by staining root tips with a mixture of fluorescein diacetate and propidium iodide. The results show a good correlation between results from growth measurement and the vital stain- ing. From the comparison of the luminosity patterns generated by vital staining it is easy to determine Al-resistant varieties, revealing this technique as a powerful and fast method for determining toler- ance to Al in different varieties. Key words: aluminum toxicity – vital staining – Phaseolus vulgaris Introduction Aluminum toxicity is considered one of the major abiotic stress factors limiting crop production on acid soils in the tro- pics. Many investigations have demonstrated that toxic Al concentrations rapidly affect root elongation with root tips being the primary site of Al-induced injury (Ryan et al. 1993) and in addition Al can show early effects, which can be related to direct interaction with the plasma membrane on the cells of the epidermis or outer cortex (Horst 1995, Barceló et al. 1996, Barceló and Poschenrieder 2002). Al toxicity is usually related with acid soils and, in certain occasions, Al can ameliorate H + toxicity in some acid, but not Al-sensitive plants, as shown by Koyama et al. (1995) by vital * E-mail corresponding author: juan.barcelo@uab.es staining of root tips of Arabidopsis thaliana with fluorescein diacetate and propidium iodide. A number of recent findings point to the plasma membrane as the primary target of aluminum toxicity. Peixoto et al. (2001) showed that Al can interact with the plasma membrane and that this interaction could lead to impaired membrane per- formance by production of higher reactive oxygen species and higher fatty acid peroxidation of the plasma membrane in Al-sensitive cultivars. Jones and Kochian (1997) suggest that the toxic mode of Al may be through the interaction with spe- cific membrane lipids by a chain peroxidation that can lead to a loss of membrane integrity and membrane protein function (Suhaida and Haug 1986, Svenningsson and Liljenberg 1986). In this way, Koyama et al. (1995) have used a mixture of fluorescein diacetate and propidium iodide to study cell damage by toxic agents. Basically, it is thought that the per- 0176-1617/03/160/12-1447 $ 15.00/0