Growing medicinal plants in hydroponic culture

Medicinal plants are increasingly cultivated on a commercial scale to satisfy the large demand for natural remedies. These species are generally grown in open field, which results in large year-to-year variability in both biomass production and content of active principles. Hydroponic technology may be applied to produce highstandard plant material all year-round in consideration of the possibility to control growing conditions and to stimulate secondary metabolism by appropriate manipulation of mineral nutrition. A series of experiments were conducted between 2005 and 2010 at the University of Pisa to investigate the application of the floating raft growing system for the greenhouse cultivation of echinacea (Echinacea angustifolia DC) and basil (Ocimum basilicum L), which are typically cultivated for their roots and leaves, respectively. Growth and content of distinctive caffeic acid derivatives (CADs), specifically echinacoside in echinacea and rosmarinic acid in basil, were determined. Both species grew rapidly and healthy and in two to four months they accumulated large biomass with minimal contamination. Nevertheless, in echinacea the high biomass production was not associated with high levels of CADs and the concentration of echinacoside (the marker compound used for quality standardization) never reached the minimum standard (1% on a dry weight basis) for the industrial production of dry extract. In contrast, basil accumulated an adequate content of rosmarinic acid. One additional advantage was the possibility to harvest also the root system of basil, which contained higher levels of rosmarinic acid compared to the leaves.