In vitro regeneration and the antioxidant enzymatic system on acclimatization of micropropagated Vitex trifolia L.

Abstract

The objective of the study was to develop an in vitro shoot regeneration protocol by utilising shoot tips explant from Vitex trifolia L. Shoot tip explants obtained from a 3-year old plant was cultured on Murashige and Skoog (MS) medium supplemented with various concentrations (1.0, 2.5, 5.0, 7.5 or 10.0 µM) of thidiazuron (TDZ). The optimal level of TDZ supplementation to the culture medium was 5.0 μM for 15 d induction period. The highest number of shoots (22.2 ± 0.1) and shoot length (5.1 ± 0.1 cm) were achieved when TDZ-exposed explants were sub-cultured on MS medium containing 6-benzyladenine (1.0 µM) and 0.5 µM α-naphthalene acetic acid (NAA) after 8 weeks of culture. In vitro rooting of isolated shoots was achieved best in half-strength MS medium containing 0.5 µM NAA. During the acclimatization period, changes in activities of antioxidant enzymes were observed. Superoxide dismutase activity increased reaching maximum at 28th day after transplantation. Likewise, an upregulation of the catalase, ascorbate peroxidase and glutathione reductase enzyme activities were also observed. These observed changes reflected the ability of plants in developing an antioxidant enzymatic defence system aiding in survival against oxidative stress and in reducing release of free radicals. Plantlets were successfully hardened off and acclimatized in earthen pots containing garden soil with a survival rate of 90 %.