Interactive effects of melatonin and salicylic acid on Brassica napus under drought condition

Abstract

It is imperative to understand the synergetic actions of Melatonin (MET) and salicylic acid (SA) in counteracting drought stress. A pot experiment was performed to investigate the interactive effects of exogenously applied MET and SA on morphology, physiology, and biochemical characteristics of drought-stressed canola (Brassica napus). Two cultivars (Super canola and Faisal canola) were used. MET (0.1 µM) and SA (0.50 mM) were applied as seed priming and foliar spray. Plants were exposed to severe drought (45% field capacity) at the reproductive stage. Drought stress caused a significant reduction in shoot length (19%), plant fresh (15%) and dry (17%) biomass, yield (30%), photosynthetic rate (43%), water potential (29%) and osmotic potential (33%) values. Increased activity of free amino acids (20%), total soluble sugars (5%), and different antioxidant enzymes like catalase (27%), peroxidase (23%), superoxide dismutase (20%) and ascorbate peroxidase (35%), were recorded under drought. Seed priming and foliar application of MET and SA reduced the negativity of drought. Priming of seeds with MET, as well as synergetic application of MET priming and SA foliar spray, were the most effective treatments, showing the most significant growth criteria (22% increase in plant height, 46% in fresh and 40% in dry biomass), yield components (49%), water (54%) and osmotic potential (28%), and endogenous MET (17%) and SA (16%) content. Super canola cultivar showed better growth than Faisal canola. Study showed that the synergetic application of MET and SA has the potential to induce stress resistance and enhance canola plants' growth under drought.