EFFECT OF DROUGHT STRESS ON GROWTH AND ESSENTIAL OIL METABOLISM IN LEMONGRASSES

Two lemongrasses, Cymbopogon nardus (L.) Rendle var. confertiflorus (S teud.) Bor. and Cymbopogon pendulus (Steud.) Wats. were grown under mi ld and moderate water stress for 45 and 90 d. The impact of in situ dr ought stress on plants in terms of relative water content, psi, concen tration of proline, activities of PEP carboxylase and geraniol dehydro genase, and geraniol and citral biogenesis, were investigated. The res ults revealed that the species exhibited differential responses under mild and moderate stress treatments. In general, plant growth was redu ced considerably whilst the level of essential oils was maintained or enhanced. Significant induction in catalytic activity of PEP carboxyla se 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 de hydrogenase was also modulated under moisture stress. The responses va ried depending upon the level and duration of moisture stress. The obs ervations have been analyzed in terms of possible relevance of some of these responses to their drought stress adaptability/tolerance.