Adventitious shoot regeneration from stem internode explants of Verbena officinalis L., a medicinal plant

Verbena officinalis L. (vervain) is a medicinal plant that shows several biological activities, includingantimicrobial, antiinflammatory, analgesic, neuroprotective, hypnotic/sedative, gastroprotective, hepatoprotective, anticancer, cicatrizant, and antioxidant. This report describes an efficient plant regeneration system for V. officinalis via adventitious shoot development from stem internode and petiole explants. Stem internode explants were more effective than petiole explants in terms of both the number of shoots per explant and the percentages of explants forming shoots. Increasing benzyladenine (BA) concentrations steadily increased shoot formation up to 13.32 μM, but 22.22 μM BA caused a sharp decrease. The highest number of shoots (17.1 shoots per explant at 100% frequency) was obtained when 13.32 μM BA was combined with 5.71 μM indole-3-acetic acid (IAA). Rooting of the regenerated shoots was readily achieved when multiple shoots were singled out and cultured on medium containing varying concentrations of different auxins [IAA, indole-3-butyric acid (IBA), 2,4-dichlorophenoxyacetic acid (2,4-D), or naphthalene acetic acid (NAA)]. IBA was more effective in terms of the number of roots developed, producing a mean of 7.1 roots per shoot at 4.92 μM, whereas IAA was more effective for the frequency of shoots developing roots: 100% of the shoots rooted at 5.71 μM IAA. More than 90% of the regenerants survived through the hardening off process, when they were transferred to foam cups and kept under growth room conditions for 2 weeks before finally being moved to room conditions at low humidity. Approximately 3 months after the transfer to room conditions, the flowering of the regenerated plants could be observed.