1School of Biology, University College of Sciences, University of Tehran, Tehran, Iran.
2Department of Biology, Faculty of Sciences, Shahed University, Tehran, Iran.
Valerian (Valeriana officinalis L.) is an important medicinal plant that is widely exploited for its roots and rhizomes which contain valepotriates and valerenic acids (with putative pharmacological activities). Thus root proliferation of valerian is very important. The aim of this study was to establish a practical tissue culture method for rapid and large-scale induction of V. officinalis L. roots with high capacity for production of valerian phytomedicine. Explants derived from leaves, petioles, and root segments (both basal and apical) of four months aged plantlets were cultured on MS basal medium supplemented with different concentrations (0.625-5 µM) of auxin and cytokinin hormones. Then accumulation of valerenic acids and valepotriates in developed root cultures was studied to find the best yielding conditions. Maximum valerenic acids (0.84%) and valepotriates contents (7.41%) were quantified in roots developed on petiole explants and in roots formed on root basal segments in medium supplemented with 1.25 μM and 0.625 μM indole-3-acetic acid, respectively. These values were significantly (P<0.05) higher than those in roots from basal and apical root segments without plant growth regulators as control. The highest average number (29.00) of directly formed roots developed on leaf explants in media supplemented with 5 μM α- naphthalene acetic acid. Also maximum number of indirectly developed roots (30.05) was observed on root apical segments in media containing 2.5 μM α- naphthalene acetic acid. These results suggest that besides the applied plant growth regulators, the type of primary explant is also relevant for biosynthetic capacity of these metabolites in root cultures.