Effect of drought stress on growth and essential oil metabolism in lemongrasses.

Two lemongrasses. Cymbopogon nardus. (L.) Rendle var. confertiflorus (Steud.) Bor. and Cymbopogon pendulus (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 content, $pS, concentration of proline, activities of PEP carboxylase and geraniol dehydrogenase, and geraniol and citral biogenesis, were investigated. The results revealed that the specific 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 PKP 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.