Effect of Application Methods of Salicylic Acid on Morphological Characteristics, Grain Yield and Essential Oil of Black Cumin (Nigella Sativa L.) under Water Stress Conditions

Black cumin (Nigella sativa L.) is an annual plant from the buttercup family that has been used in food industry and cosmetic products in addition to its medicinal value. It is well known that abiotic stresses especially drought stress are very restrictive factors for agricultural production around the world. Drought stress affects a vast range of morphological, physiological and biochemical characteristics of plants. Due to the decrease and shortage of agricultural water resources, researchers have conducted various researches to find materials that increase the efficiency of water use and maintenance in plants. One of these compounds is salicylic acid, and this material is naturally present in most plants and affects many physiological activities of the cell. Due to the decrease and shortage of agricultural water resources, researchers have conducted various researches to find materials that increase the efficiency of water use and maintenance in plants. One of these compounds is salicylic acid, and this material is naturally present in most plants and affects many physiological activities of the cell. Salicylic acid is a naturally occurring plant hormone that controls plant growth and induces water deficit tolerance in plants. One of these compounds is salicylic acid, and this material is naturally present in most plants and affects many physiological activities of the cell. Salicylic acid is a naturally occurring plant hormone that controls plant growth and induces water deficit tolerance in plants.

This study was conducted based on randomized complete design with factorial arrangement of treatment and three replications at research field of Gonbad Kavous University, Iran in 2018 winter and spring. Different irrigation regimes at four levels including no irrigation (dry farming), once irrigation at flowering stage, once irrigation at grain filling stage and twice irrigation at flowering and grain filling stages as well as salicylic acid factor at three levels including no application (control), seed priming (with 0.5 mM concentration), foliar spraying (with 0.5 mM concentration) were studied. After application of the treatments, the necessary sampling was done and the traits such as plant height, number of lateral branches, number of follicle per plant, number of seeds per follicle, weight of follicle per plant, plant dry weight, essential oil content, essential oil yield and, finally, grain yield in the plant were evaluated. Statistical calculations were performed using SAS 9.1 software. The mean of studied traits was also compared by using the least significant difference between the protected LSD at 5% probability level. The required graphs were also drawn using Excel software.

The results showed that simple effects of irrigation and salicylic acid on all traits were significant. The effects of irrigation and salicylic acid on all studied traits were also significant, except essential oil percentage and essential oil yield. The use of salicylic acid increased morphological traits. Also, the effects of irrigation and salicylic acid on all studied traits were significant, except essential oil percentage and essential oil yield. The use of salicylic acid increased morphological traits. The highest amount of essential oil and essential oil yield in irrigation levels were related to the irrigation at filling stage (0.65%) and twice irrigation at flowering and grain filling stages (7.93 kg ha-1), respectively. Salicylic acid treatment was the most essential oil and essential oil yield for salting. The highest grain yield (1330 kg ha-1) was obtained in foliar spraying application of salicylic acid under twice irrigated conditions and the lowest grain yield (817 kg ha-1) was obtained in non-application of salicylic acid at dry farming conditions.

Salicylic acid is able to reduce the negative effects of drought stress on black cumin plant. In general, the results showed that by using salicylic acid in the form of foliar application and twice irrigation, optimal yield of black cumin was achieved.