Dynamics of essential oil biosynthesis in relation to inflorescence and glandular ontogeny in <i>Salvia sclarea</i>

Abstract

Abstract Changes in the essential oil concentration, composition and glandular morphology of Salvia sclarea L. were studied at different stages of inflorescence maturity. The chemical composition of oil was determined by GC–MS, NMR and the peak enrichment technique. The oil yield at bud stage on a fresh basis was minimum (0.08%), peaked at full bloom stage (0.18%) and was followed by sharp decline on maturation (0.07%). The main components of the oil were linalool (36.6–41.9%) and linalyl acetate (13.2–19.2%). The maximum percentage composition of various constituents was coincident with full bloom stage. β ‐Humulene (6.4–8.9%), α ‐cadinene (t–1.5%), β ‐caryophyllene (t–1.4%), β ‐caryophyllene oxide (0.4–1.4%) and sclareol (0.3–1.8%) present in the oil showed gradual increase in percentage over the different stages of maturity, with no significant turnover losses at maturation stage. Turnover of essential oil (61.1% loss) and monoterpenes (23.6% loss) occurred late in development at full maturity. Scanning electron microscopy (SEM) was used to follow the changes in the oil secretory glands over different temporal phases of maturation. The decline in oil concentration and monoterpene constituents compared very well with the observed deterioration and lyses of secretory glandular system. An abrupt fall in oil concentration apparently appears due to differential evaporation of the more volatile constituents, rather than as a dynamic balance between biosynthetic and catabolic processes.