Ameliorative role of salicylic acid on morpho-anatomy and physiology of rapeseed (Brassica napus L.) under lead stress

Heavy metals, due to their pervasiveness is serious threat to crop productivity. Lead (Pb) is an incredibly toxic and unnecessary heavy metal that makes its entry into the plants via contaminated soil. Salicylic acid (SA), a plant-derived hormone has the ability to assist pants to strengthen their immune system against toxic metals like lead (Pb). This research intends to investigate the alleviating impact of salicylic acid on the morphology, anatomy and physiology of B. napus (rapeseed) plants during the toxicity of lead (Pb). The plants were treated with 3 levels of lead (lead nitrate) i.e. 1 mM, 2 mM, and 4 mM along with salicylic acid and without salicylic acid. Two levels of salicylic acid i.e. 0.5 mM and 1 mM were used in the form of foliar spray. The results indicated that Pb induced damage is alleviated by SA and the morphological traits were improved i.e root length (58%), shoot length (16%), root fresh weight (73%), shoot fresh weight (79%) and dry weight of root (66%) and shoot (74%), number of leaves (87%), leaf area (61%), and yield (78%) as compared to Pb stress. Similarly, the anatomical features i.e. epidermal thickness (46-63%), vascular tissue area (42-54%), cellular thickness (27-59%) of the plant also improved with SA treatment in comparison to Pb stress. The physiological parameter i.e chlorophyll pigments (chlorophyll a, b and total chlorophyll) were also increased by 2-4% with SA as compared to Pb toxicity. However, the higher level of SA (1 mM) proved less beneficial as compared to the lower level (0.5 mM) in mitigating the effects caused by stress. According to these outcomes, SA could serve as a helpful approach for enhancing the tolerance of B. napus to withstand stressed conditions, hence improving crop resilience in Pb-containing soils.