Evaluation of salicylic acid application on the physiological responses of black cumin (Nigella sativa L.) under different irrigation conditions

To investigate the effects of foliar spraying and pretreatment with salicylic acid on some physiological traits and grain yield of Black Cumin (Nigella sativa L.) under different irrigation regime, the study was conducted based on randomized complete blocks design with factorial arrangement of treatment and three replications in Gonbad Kavous university research field in 2017-2018. The treatment included four irrigation levels: without irrigation (dry farm), irrigation at flowering stage, irrigation at seed filling stage and two irrigations at flowering and seed filling stages and salicylic acid application included three levels: non- application of salicylic acid (control), priming with salicylic acid (0.5 mM -1) and foliar spraying of salicylic acid (0.5 mM -1). In this study, some traits such as amount of chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, electrolyte leakage, proline, soluble sugars and grain yield were evaluated. The results showed that the effects of simple irrigation and salicylic acid and their interactions on all studied traits were significant. The results of the comparison of mean interactions showed that the application of salicylic acid in form of foliar spraying increased traits such as photosynthetic pigments, proline, soluble sugars and grain yield in all irrigation conditions. Priming with salicylic acid treatment had the lowest electrolyte leakage. 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 was obtained (817 kg. ha-1) in non-application of salicylic acid at dry farm conditions. According to the results of this study, it can be concluded that the application of salicylic acid as foliar spraying is a suitable strategy for increasing the resistance of black cumin to drought stress.