Exploring the morpho-physiological responses of maize to nickel stress modulated by salicylic acid

Salicylic acid (SA) is an important phytohormone essential for the regulation of plant growth, development, ripening, and defense responses. The role of SA in plant–pathogen interactions has attracted a lot of attention. Aside from defense responses, SA is also important in responding abiotic stimuli. It has been proposed to have great potential for improving the stress resistance of major agricultural crops. On the other hand, SA utilization is dependent on the dosage of the applied SA, the technique of application, and the status of the plants (e.g., developmental stage and acclimation). Here, the effects of exogenously applied SA (0, 0.15 and 0.30 mM) as foliar spray under nickel (Ni) stress (0 and 700 µM) in root growing medium were studied on two maize varieties (C-20 and EV-79). The experiment was conducted using a three-factor factorial design with three replicates and watering 1L Hoagland’s nutrient solution/day. Ni stress decreased the number of leaves per plant, flag leaf area, total chlorophyll contents, carotenoids, K⁺, Ca²⁺ and P accumulation in stem, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity, while enhanced the accumulation of total soluble proteins (TSP), total phenolics, ascorbic acid contents and Na⁺ ion accumulation in both varieties of maize. Exogenously applied SA increased the number of leaves per plant, flag leaf area, chlorophyll contents, K⁺, Ca²⁺ and P accumulation, SOD, POD and CAT activity, total phenolics and ascorbic acid contents and TSP. SA application reduced the Na⁺ ion accumulation in both maize varieties. A varietal difference was observed in all attributes, and variety C-20 was proved to be more resistant as compared to variety EV-79. Overall, the research aims to contribute to the understanding of how the exogenous application of salicylic acid influenced morpho-physiological responses of maize for enhancing the tolerance of maize to heavy metal stress.

Graphic abstract