Changes in Essential Oil Quantity and Quality Influenced by Ontogenetic Factors

Connection between the developmental stage and the quantity and quality of essential oil was investigated in some model species of the Asteraceae, Lamiaceae and Apiaceae plant families. The accumulation of essential oil decreased continuously during ontogenesis in Tanacetum vulgare. The tendency of accumulation showed an optimum curve in Mentha piperita, Hyssopus officinalis, Majorana hortensis, with a maximum bound to the flowering stage. However, the actual maximum may be influenced by ecological and agrotechnological factors. In the case of Carum carvi and Foeniculum vulgare, the accumulation tendency can be characterised by parallel optimum curves in vegetative and generative organs, with maximum points at different times and different levels. The composition of essential oil of Achillea species during the leaf rosette stage was characterised by the abundant presence of sesquiterpenes, while after the generative differentiation the monoterpenes became dominant. In families Lamiaceae and Apiaceae the compositional changes are continuous not influencing determination of chemotypes. Alterations in composition of the essential oil may be based on structural changes of accumulation organelles or originating from modifications in biosynthesis or metabolization of synthesised products. INTRODUCTION Chemical diversity of essential oil producing species is a wellknown phenomenon. Recently, we have conducted a large series of investigations on the specialities and regularities of these chemotaxonomical changes both in quantitative and qualitative respects, focusing mainly on three families: Asteraceae, Lamiaceae and Apiaceae. Oil Accumulation Ruminska (1970) declared that essential oil content of Asteraceae species were highest at full flowering stage, however data for Achillea species and T. vulgare was not available. For peppermint, some authors found the highest value of essential oil content at the beginning of blossoming (Hornok, 1978; Clark and Menary, 1979), other authors found the essential oil content highest at full flowering time (Singh et al., 1995; Malizia et al., 1996). In fennel, Paukov et al. (1971) found a twenty-fold increase in essential oil content from budding till waxy ripening and Tóth (1967) reported the green-fruit stage as optimal for essential oil extraction. However, Cavaleiro et al. (1993) measured a double essential oil content in the ripen fruits compared to the green ones. Similarly, Gupta et al. (1995) mentioned the ripen fruit stage as assuring the highest level of essential oil. Compositional Changes In A. millefolium both Ruminska (1970) and Usztojzsanin et al. (1987) measured a maximum of chamazulene during early bud stage. Cernaj et al. (1983), however, determined the highest chamazulene level at full flowering. In the level of the studied four monoterpenes (αand β-pinene, limonene, sabinene) alterations between the vegetative Proc. WOCMAP III, Vol. 1: Bioprospecting & Ethnopharmacology Eds. J. Bernáth, É. Németh, L.E. Craker and Z.E.Gardner Acta Hort 675, ISHS 2005 160 and generative phase proved to be significant, changes during flowering were slighter. Similar information in our model species (A. pannonica, A. ochroleuca and A. crithmifolia) were not known. In Tanacetum vulgare, Schantz et al. (1966) reported small quantitative changes (5-15%) of the main components of the essential oil from green bud stage till the end of flowering. In peppermint and Chalchat et al. (1997) proved a continuous increase of menthol content in developing shoots. According Farooqi et al. (1999), after full flowering a decrease in menthol can be measured. In hyssop, Schulz and Stahl-Biskup (1991) found no significant compositional changes occur between vegetative and flowering shoots. On the contrary, Tsankova et al. (1993) reported the decrease of cineole (by 9%) and isopiocamphone (by 12%) in the leaves during flowering. During ontogenesis of fennel, Tóth (1967) and Trenkle (1972) found a decrease of anethole, fenchone and estragole in older shoots, while their proportion increased in the fruits. The tendencies for phellandrene and limonene are opposite. Cavaleiro et al. (1993) however, did not find significant differences in the proportion of these three major components during the fruit development. MATERIAL AND METHODS For the examination of accumulation dynamics and composition of essential oil, the model populations had been investigated at different phenological phases as follows. Aboveground parts of Tanacetum vulgare (Asteraceae) chemotypes were sampled after sprouting out; at a stage of 30-40 cm vegetative shoots; at budding stage; at the beginning of flowering; at full flowering and at the seed ripening stage (Németh et al., 1994). Aboveground parts of Achillea species (A. pannonica, ochroleuca and crithmifolia) were cut at leaf-rosette stage; at 20-30cm height of the shoots; at budding stage and at full flowering (Zámboriné, 1996). The shoots of Hyssopus officinalis (Lamiaceae) were investigated from the vegetative stage after shooting through the seed ripening phase. Three populations (Hungarian cultivar ‘Kékvirágú’, gene bank materials of German origin, and a commercial material ‘Bulgarische Auslese’ were studied during two growing seasons (Németh et al., 2001). In Mentha piperita the cultivar ‘Mitcham’ was studied, sampling the flowering shoots during the generative phases from budding till the end of flowering (Zámboriné and Tétényi, 1988). In Foeniculum vulgare (Apiaceae) the vegetative parts and the generative parts were studied separately. During ontogenesis, the vegetative organs of cultivar ‘Soroksari’ had been sampled after shooting, before flowering and at full flowering. The generative parts were studied from the green bud stage through fruit ripening at nine different stages (Bernáth et al., 1999). All of the samples were hydro-distilled according to the PhHgVII, and the main components of the oils were determined by capillary GC method (Bernáth et al., 1999).