ABSTRACT

Accumulation of essential oils in plant tissue culture is the result of de novo synthesis, and in many cases the type and proportion of their components differ greatly from those in the parent tissues. There are some external factors that influences this synthesis, such as long-day which enhances the growth and the amount of essence. The diversification of the components depends on the light/dark relation and temperature. The oxidation-reduction level of monoterpenes is related with the oxidation-reduction state of respiratory coenzymes of the producing cells. The deficiency of P or N reduces the growth but increases the content of the essential oil by 18% and 29%, respectively. Micropropagated plantlets cultured without plant regulators in LS medium or in LS medium containing 0.1 mg 1^-1BA and/or IBA showed that the addition of BA inhibited the formation of the glands by 44% compared with the control plantlets and also inhibited their development ; these plantlets had the highest number of unbroken glands (in pre-secretory state) when compared with plantlets grown in other conditions. The presence of BA stimulated chloroplast formation and increased the essential oil content by 150% with respect to the control plants. BA also increased their secretion, and the number of lipid droplets in the chloroplasts, cytosol and plasmalemma. On the contrary, the presence of IBA decreased the essential oil concentration in plantlets by 31% when compared with the control and inhibited their secretion capacity. All these plantlets showed a positive correlation between oil accumulation and the percentage of glandular hair in the secretory stage. Quantitative changes in the major monoterpene components (1,8 cineole, fenchol, borneol and camphor) and sesquiterpene content of plantlet oil were also observed in response to the effect of varying growth regulator concentration in the culture medium.