In vitro culture of sweet basil: gas exchanges, growth, and rosmarinic acid production

Five in vitro culture systems with different ventilation rates were used to investigate the influence of vessel environment on photosynthesis, dark respiration, ethylene evolution, and rosmarinic acid (RA) production in sweet basil (Ocimum basilicum L.) micropropagated shoots. The systems under comparison were two bioreactors with either temporary (RITA™) or stationary (Growtek™) immersion, and three types of vessels (Magenta™, Microbox ECO2™, and PCCV25™) that are largely used for plant micropropagation. Shoots of green-leaved cv. Genovese and purple-leaved cv. Dark Opal were cultured on a modified Murashige and Skoog medium containing 0.25 mg dm−3 6-benzylaminopurine. The instantaneous rates of photosynthesis, dark respiration, and ethylene production were determined by gas chromatography measuring CO2 and ethylene concentrations in vessel headspaces. The tissue RA content was determined by HPLC in HCl-methanol extracts. The explant growth and morphology were significantly affected by culture conditions and cultivars. The largest biomass production was observed under the photomixotrophic culture conditions provided by Growtek™, whereas the highest RA content in shoot tissues was found in the RITA™ photomixotrophic system, where ethylene accumulated to the greatest extent.