Effects of salicylic acid on physiological, biochemical, nutrient uptake, and essential oil percentage of Ocimum basilicum cv. Keshkeni luvelou under salinity stress

Basil (Ocimum basilicum L.) is one of the important plants from Lamiaceae family which is used as a medicinal spicy plant and also as a fresh vegetable. Salicylic acid (SA) is one of the most important plant growth regulators that regulates growth and physiological development and metabolic processes of the plant. Its application under salinity stress conditions decreases the effects of salinity toxicity and makes resistance in the plants. To investigate the basil (O. basilicum cv. Keshkeny luvelou) physiological and biochemical responses to salinity stress and SA, a factorial pot experiment was conducted based on a completely randomized design with three replications in the research greenhouse of Vali-e-Asr University of Rafsanjan. Experimental treatments included salinity at four levels (0, 30 ,60, and 90 mM) and SA at five levels (0, 0.5, 1, 1.5, and 2 mM). The results showed that salinity stress reduced the amount of chlorophyll florescence, chlorophylls a and b, total chlorophyll, carotenoid, relative water content, and essential oil percentage. The SA treatment decreased the negative effects of salinity stress on the plant and improved essential oil percentage. Also, salinity stress increased the amount of proline, soluble carbohydrate, phenol, antioxidant activity, electrolyte leakage, leaf and root sodium, and chlorine, but the SA treatment at some salinity stress levels caused to decrease and/or increase these traits. Overall, SA improved the physiological and biochemical characteristics of basil under salinity stress through increasing osmolytes production and resulted in increasing nutrient uptake and essential oil percentage of the plant.