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Water hyssop (Bacopa monnieri L. Pennel) is a medicinal aquatic herb used to treat diseases in South Asia. Various regeneration protocols have been developed or modified in vitro to ensure the availability of biomass and secondary metabolites of Bacopa. We applied hydrothermally treated titanium dioxide (TiO2) nanoparticles (NPs) (TiO2-NPs) at different concentrations. Three explants, distal portion of half leaf (DPHL), proximal portion of half leaf (PPHL) and full leaf (FL), were used to evaluate response to TiO2. Regeneration from the three explants in vitro was similar except for shoot length. Application of TiO2-NPs exerted significant, but variable, effects on all parameters except percentage of shoot formation, which was 100%. Interactive effects of explant and TiO2-NPs exhibited significant, but variable, effects on fresh weight and percentage of callus formation. All explants produced more shoots using TiO2-NPs compared to control treatments. DPHL explants with application of 8 mg/l TiO2 produced more shoots than controls. Similarly, FL explant treated with 2 mg/l TiO2-NPs produced more shoots/explant than controls. All concentrations of TiO2-NPs produced significantly longer shoots compared to controls. Increased elongation of shoots justifies use of TiO2-NPs for propagation of plants in vitro during acclimatization. Use of TiO2-NPs for rapid elongation of shoots ultimately fosters survival of plants. [ABSTRACT FROM AUTHOR]

Water hyssop (Bacopa monnieri (L.) Pennell) is a medicinal plants. Its upper and lower halves of leaf explants were incubated in Murashige and Skoog (MS) medium supplemented with 0.25, 0.50 and 1.0 mg/L benzylaminopurine (BA) for 8 weeks; the explants were exposed to white (W) and red and blue (R and B, respectively) light-emitting diodes (LEDs), at 4:1, 3:1, 2:1 and 1:1 R and B light ratios, respectively. Shoot regeneration (100%) was achieved from all explants at all applied concentrations of BA and LED types. All explants showed different BA concentration requirements for regeneration of the maximum number of shoots. Longer shoots were obtained on medium with 0.25 mg/L BA. The W LED lighting system was found to be more effective for regenerating the maximum number of shoots (26.11) per explant (on the upper half of the leaf). Conversely, longer and shorter shoots were generated under 1:1 R:B and W LEDs, respectively. The number of shoots per explant ranged from 9.67-24.0 (full leaf), 6.33-25.92 (lower half of the leaf) and 7.33-27.33 (upper half of the leaf), respectively, in response to BA and LED light. Shoot length ranged from 0.94-1.90 cm (full lamina), 0.70-2.11 cm (lower half of the leaf) and 0.93-1.83 cm (upper half of the lamina) in response to BA and LED lifght. Regenerated shoots were successfully rooted using indole-3-butyric acid (IBA) and acclimatized in the aquarium provided with tap water.