In Vitro Hairy Root Cultures as a Tool for Phytoremediation Research

Plant model systems are needed in which to conduct basic laboratory studies prior to field applications of phytoremediation. In vitro plant cultures are a useful tool for such research purposes. This chapter focuses on the generation of hairy root cultures and their use as a laboratory root model for the in vitro study of the removal of aromatic compounds. A protocol for the generation of hairy root cultures of Armoracia lapathifolia L. by infection with Agrobacterium rhizogenes (a soil-borne bacterium that induces the differentiation of roots at the infection spots) is described. A second protocol describes the application of hairy root cultures in assays for studying the removal of organic compounds, exemplified with phenol, a model organic contaminant. A. lapathifolia roots contain high levels of peroxidases (E.C. 1.11.1.7), enzymes that are known to be involved in the detoxification of phenols and other aromatic compounds. Briefly, the cultures are exposed to different concentrations of the contaminant under study and the remaining amounts of it, and some physiological parameters, are monitored along defined time intervals. This experimental procedure permits the estimation of the capability of a plant species to remove a contaminant and also the main variables that may affect the remediation process. This information is essential for assessing the feasibility of a remediation process prior to its field application. This can be done at relatively low analytical expense and in short periods of time with the use of in vitro plant models. Hence, the hairy root culture constitutes a valuable tool for phytoremediation research and development.