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(Steud,) Wats, were grown under mild and moderate water stress for 45 and 90 d. The impact of in situ drought stress on plants in terms of relative water eontent, ^, concentration of proline, activities of PEP carboxylase and geranio! dehydrugenase, and geraniol and citral biogenesis, were investigated. The results revealed that the species exhibited differential responses under mild and moderate stress treatments. In general, plant growth was reduced considerably whilst the level of essential oils was maintained or enhanced. Significant induction in catalytic activity of PEP carboxylase under water stress was one of the consistent metabolic responses of the aromatic grasses. The major oil constituents, geraniol and citral, increased substantially in both the species. Activity of geraniol dehydrogenase was also modulated under moisture stress. The responses varied depending upon the level and duration of moisture stress. The observations have been analyzed in terms of possible relevance of some of these responses to their drought stress adaptability/tolerance.

Artemisinin and herbage yield of Artemisia annua plants were determined after application of triacontanol (tria.) and chlormequat (2-chloroethyltrimethylammonium chloride). Tria. at 1 .O and 1.5 mg ll' produced a statistically significant positive effect on artemisinin level as well as on plant height, leaf and herbage yield. Chlormequat at 1000 and 1500mgll' also increased artemisinin level, decreased the plant height at higher concentrations and increased the leaf and herbage yield at lower concentrations. Tria. application enhanced GA-like activity, but ABA levels decreased, while chlormequat increased ABA but reduced GA-like substances. The effect of Tria. on artemisinin yield seems to be mediated through its effect on plant growth.

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