Effects of jasmonic acid and 24-epi brassinolid on quantitative and qualitative yield of Nigella sativa L. under salinity stress condition

Salinity is one of the most common abiotic stresses, which causes a high decrease in crop production. Growth regulators play an important role in plant growth and development under normal and stress conditions. To study the effects of foliar application of jasmonic acid and 24-epibrassinolide on yield and yield components, oil and essential oil percentage and some physiological characteristics of black cumin (Nigella sativa L.) under salinity stress conditions, a factorial experiment based on the randomized complete block design was conducted in the research greenhouse of Mohaghegh Ardabili University with three replications. The treatments included salinity at four levels (0, 5, 10 and, 15 ds.m-1 NaCl) and plant growth regulators at three levels (control, 0.1 mmol 24-epibrassinolide, and 0.5 mmol jasmonic acid). Results of mean comparisons indicated that salinity stress decreased plant yield, number of seeds per capsule, number of capsules per plant, and seed oil percentage, while significantly increased 1000-seed weight and proline content. Growth regulators also increased 1000-seed weight and seed oil percentage and decreased proline content. Chlorophylls a and b contents of the leaves decreased with increasing salinity levels, and the use of jasmonic acid and 24-epibrassinolide increased their amounts at all salinity levels. Malondialdehyde content increased with increasing salinity levels, and plant growth regulators foliar spray decreased its content at all stress levels. Besides, the percentage of seed essential oil increased with increasing salinity levels and also with plant growth regulators application at all salinity levels. It is recommended to foliar spray the plant with 24-epibrassinolide and jasmonic acid growth regulators under salinity conditions to avoid stress damages and increase black cumin essential oil, which is a very important compound in the pharmaceutical industry, as well as to enhance seed oil percentage, 1000-seed weight, and photosynthetic pigments of black cumin.