Regeneration of plants and production of volatiles from callus cultures of Melissa officinalis L .3. Effect of exogenous growth regulators on essential oil composition.

Regenerates of lemon balm (Melissa officinalis L., Lamiaceae) have been established to serve as in-vitro-system to study the effects of selected exogenous growth regulators. In this communication we report the efficiency of NAA, BAP, and ABA on morphology and essential oil composition. Long term cultivation only leads to changes of minor compounds in relation to total essential oil. Citronellal, citronellol, nerol, and geraniol are elevated whereas geranyl acetate is depressed. The essential oil of plants growing under the influence of NAA exhibit comparable changes of citronellal, citronellol, and geranyl acetate. Therefore it refers to plants belonging to an advanced stage of development. Nutrition media supplemented with high concentration of BAP induce plants to accumulate more than 10% alloaromadendren. This sesquiterpenehydrocarbon is only a trace compound in control plants and has not been described before for the essential leaf oil of naturally grown Melissa officinalis. Beside a small effect of ABA to the production of some minor compounds it shows a synergistic effect in combination with BAP. In this case only the BAP-specific changes are expressed at a BAP-concentration that leads to negligible changes in single application. We could demonstrate the induction of an unusual alloaromadendren-type of essential oil obtained from lemon balm.