Strong genetic control of artemisinin has been demonstrated by broad-sense (24) and narrow-sense heritability (25), indicating that genes, rather than the environment, account for most of the artemisinin production of the plant. Approaches to increase artemisinin in artemisia under in vivo conditions have included water stress (26), the development of tetraploids (27), and foliar application of half-strength Hoagland solution containing gibberellic acid (GA3) to sand-potted plants (28). The total artemisinin (g/plant) decreased in the first two studies. In the third study, the artemisinin concentration increased almost five-fold, from 0.14 (g/100 g) to 0.64% with 14 íM GA3. However, artemisinic acid decreased from 0.59 to 0.21% at the same GA3 concentration.