Submitted to: Brazilian Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2010
Publication Date: 6/8/2010
Citation: Marchese, J.A., Ferreira, J.F., Rehder, V., Rodrigues, O. 2010. Water deficit on the accumulation of biomass and artemisinin in annual wormwood (Artemisia annua L., Asteraceae). Brazilian Journal of Plant Physiology. 22(1):1-9. Interpretive Summary: Sweet wormwood (Artemisia annua) is the only source of the antimalarial artemisinin, effective in the treatment of malaria and other parasitic diseases that afflict humans and animals. Although long-term drought can severely reduce the leaf biomass and artemisinin accumulation in the plant, there is no data reporting the effect of a short-term drought on leaf biomass and artemisinin accumulation. Plants were cultivated in soil under growth chamber conditions and deprived of water for 14, 38, 62, and 86 hours. Artemisinin concentration and leaf biomass were evaluated and compared to an irrigated control. Water deprivation of 38 and 62 hours resulted in higher leaf artemisinin concentration, but only the 38-h deprivation led to a statistically significant increase of 29% in both leaf and total plant artemisinin, without harming leaf biomass accumulation. The other treatments either had no effect or decreased artemisinin leaf concentration. Upon irrigation at the end of the experiment, plants recuperated well from all water deprivation treatments. Results indicate that moderate water deprivation before the crop is harvested can be beneficial by increasing the concentration of artemisinin in the plant. A short drought before harvesting also decrease post-harvest costs with plant drying before industrial extraction. In addition, results indicate that artemisinin could be part of the plant’s chemical system of defense against water deprivation.
Technical Abstract: Despite the importance of Artemisia annua as the only source of the anti-parasitic drug artemisinin, little can be found on the role of biotic and abiotic stress on artemisinin. Water stress is the most limiting factor on plant growth, but can trigger secondary metabolite accumulation, depending on the plant growth stage. Artemisia annua cultivated in growth chambers was submitted to five water deficit treatments (watered, 14, 38, 62 e 86 hours without irrigation). Water deficits (measured as xylem water potential or XWP) of 38 and 62 hours (XWP = -1.39 and -2.51 MPa, respectively) increased leaf artemisinin content, but only 38 hours led to a significant increase (29%) in both leaf and plant artemisinin, with no detriment to plant biomass accumulation. The other treatments had no effect on, or decreased, artemisinin accumulation. A. annua plants tolerated water deficit treatments well, including the most severe water deficit applied (XWP = -3.97 Mpa or 86 hours after irrigation) and recovered their turgor pressure after rehydration. These results suggest that moderate water deficit prior to harvesting the crop may not only reduce time and costs in drying the crop, but can also induce artemisinin accumulation, both of which increase crop profit margins. Results also suggest that artemisinin could be part of A. annua chemical system of defense against water stress.