Abstract
The objective of the current study was to monitor the variations caused by the application of exogenous melatonin on growth kinetics and production of stress enzymes in Prunella vulgaris. Leaf and petiole explants were used for callogenesis. These explants were inoculated on Murashige and Skoog media containing various concentrations of melatonin alone or in combination with 2.0 mg/l naphthalene acetic acid. Herein, a maximum of 3.18-g/100 ml fresh biomass accumulation was observed on day 35 during log phase of growth kinetics at 1.0 mg/l melatonin concentration from leaf explants. While 0.5 and 1.0 mg/l melatonin enhanced the biomass accumulation from petiole explants. Moreover, the synergistic combination of melatonin and naphthalene acetic acid also promoted growth from leaf and petiole explants. Leaf derived callus cultures treated with 1.0 mg/l melatonin induced the production of total protein content (90.47 μg BSAE/mg FW) and protease activity (4.77 U/g FW). While the calli obtained from petiole explants have shown highest content of total protein (160.8 μg BSAE/mg FW) and protease activity (5.35 U/g FW) on media containing 0.5 mg/l melatonin. Similarly, 0.5 mg/l melatonin enhanced superoxide dismutase (3.011 nM/min/mg FW) and peroxidase (1.73 nM/min/mg FW) enzymes from leaf derived callus cultures. The combination of 1.0 and 1.5 mg/l naphthalene acetic acid enhanced content of total protein and protease activity in leaf and petiole derived cultures. These results suggested that the application of melatonin play a positive role in biomass accumulation and production of stress enzymes in P. vulgaris.