The production of secondary metabolites has been associated with increased levels of reactive oxygen species (ROS), which are byproducts of aerobic metabolism, or with biotic (insect, pathogen attack, and herbivores) and abiotic (drought, extreme temperatures, nutrient deprivation, and others) stresses (29-31). It has been hypothesized that ROS triggered by stress in artemisia are scavenged by dihydroartemisinic acid, which in turn is converted into artemisinin as a final, stable end product (32). In Africa, the main cultivated A. annua cultivars (Artemis and A-3) are provided by Swiss- (25) and German-based organizations, respectively, although some Nigerian growers are currently testing a cultivar (3M) from the University of Campinas, Brazil.
The objectives of this study were to evaluate the effect of stresses associated with low pH and macronutrient deficiencies on the accumulation of leaf biomass, artemisinin (Figure 1A), and its precursors, dihydroartemisinic acid and artemisinic acid (Figure 1B), in A. annua plants grown on a dystrophic West Virginia soil under greenhouse conditions.