Effects of drought stress on quantitative and qualitative yield, physiological characteristics and essential oil of Ocimum basilicum L. and Ocimum americanum L

In order to evaluate the effects of drought stress on quantity and quality of yield, physiological characteristics, and essential oil of Ocimum basilicum L. and Ocimum americanum L., a factorial experiment was carried out in a randomized complete block design with three replications in greenhouse condition. Drought stress treatments consisted of control (without drought stress), 80, 60, and 40% of field capacity on two species of Ocimum. The traits measured were fresh and dry weights, essential oil, essential oil performance, carbohydrates, proline, nitrogen, protein, phosphorus and potassium contents. The results indicated that with increasing levels of drought stress from control to 40 percent of field capacity, the content of essential oil, carbohydrates, and proline were increased (28, 46, and 50%) in both species. However, the content of fresh and dry weight, essential performance, nitrogen, protein, phosphorus and potassium were reduced (57, 57.8, 44, 19, 16, 39 and 23%). In O. americanum, the content of fresh and dry weight, carbohydrate, proline, nitrogen, phosphorus, and protein were significantly increased under drought stress; while in O. basilicum, only essential oil content showed higher values significantly. It was observed that the majority of growth factors had the highest performance under low stress (80% of field capacity). Essential oil content, on the other hand, increased significantly under high stress condition, so that in O. basilicum, the highest essential oil content was obtained at 60 percent of field capacity. Our findings indicated that the plant performance and essential oil content were increased under average and moderately severe stress conditions, respectively.