Drought stress increases the accumulation of monoterpenes in sage (<em>Salvia officinalis</em>), an effect that is compensated by elevated carbon dioxide concentration

Abstract

The infliuence of drought stress on the accumulation of cineole, camphor and α/ß-thujone in sage plants (Salvia officinalis L.) was determined by comparing the content of monoterpenes of wellwatered plants and those restricted in irrigation (70% of the optimal water supply). In order to modulate the impact of drought stress, these plants were cultivated either at ambient or elevated CO₂ concentrations (385 ppm or 700 ppm).
Leaves of sage grown under moderate drought stress reveal significant higher concentrations of monoterpenes (about 33%) than those of plants cultivated under well watered conditions. Under ambient CO₂, also the total content of monoterpenes per plant is higher in the stressed plants than in the well-watered ones. The enrichment of the CO₂-concentration, which is thought to impair the metabolic effects of drought stress, resulted in a marked decrease in the monoterpene concentration, i.e., 17.8% in the case of well watered plants, and 21.8% in the drought trial. From this it is deduced that the increased reduction capacity arising from drought stress, pushed metabolic activity towards the biosynthesis of highly reduced compounds.