Changes in essential oil and physiological parameters of callus and seedlings of Carum copticum L. under in vitro drought stress

Drought stress exerts a considerable influence on the production of secondary metabolites, which have interesting biological properties and quite a number are of medicinal importance, in plants. Secondary metabolites also are unique sources for food additives, flavors and industrially important biochemical. They play a major role in the adaptation of plants to the environment and overcoming stress conditions. This study was carried out to elucidate the mechanism of drought stress in seedlings and calli of Carum copticum under in vitro condition by evaluating the physiological and enzymatic activities, and secondary metabolites. Seedlings of C. copticum were cultured in MS medium containing 0, 3 and 6% mannitol and calli were cultured in MS medium containing 1 A mu M 2,4-d, 4 A mu M BAP and different levels of mannitol (0, 3 and 6%). After 4 weeks, the enzymatic and physiological parameters were measured by adapting spectrophotometrically and the GC/MS was used for the identification of secondary metabolites. Drought stress induced by mannitol caused a progressive increase of proline and carbohydrates contents in both seedlings and calli and the activation of CAT and SOD enzymes. In addition, drought stress effected the essential oil compounds of seedlings and callus. As compared to the control, mannitol enhanced the percentage of thymol in seedlings and callus under treatment (18.7 and 20.8%) and gamma-terpinene (20.0 and 24.6%) as major components. In vitro drought stress induced by mannitol effected the biochemical, physiological and metabolic responses, suggesting that its beneficial effect can be exerted on the main essential oil contents.