Unraveling the underlying mechanisms of biochemical, physiological, and growth responses of two pea (Pisum sativum L.) cultivars under simulated acid rain-induced oxidative stress

The current experiment was designed to evaluate the ramifications of simulated acid rain (SAR) on two pea (Pisum sativum L.) cultivars, Kashi Samridhi (Samridhi) and Kashi Nandini (Nandini), to decipher the intraspecific variations in defence mechanism considering the current scenario of rapid anthropogenic activities leading to increase in rain acidity. The pea cultivars were subjected to SAR of pH 7 (Control), 5.6, 5.0, and 4.5 under field conditions. SAR increased active oxygen species and malondialdehyde content due to increased lipid peroxidation in both cultivars; however, the increment intensity was more remarkable in Samridhi at the later growth stage. Ascorbic acid, thiol, and flavonoids were significantly increased in cultivar Nandini, along with increased peroxidase and superoxide dismutase activities. Total phenolics, glutathione reductase, and ascorbate peroxidase activities were enhanced considerably in Samridhi than in Nandini under SAR treatments. Higher stomatal density and stomatal size in Samridhi prompted greater acidic particles influx which further damaged the chloroplast and mitochondria. The present study concludes that cultivar Nandini is more proficient in inducing defence responses by elevating non-enzymatic antioxidants than Samridhi. Non-enzymatic linked defence mechanisms are more metabolically expensive, leading to less biomass accumulation in Nandini. The study depicted that innate defence responses, particularly the role of non-enzymatic antioxidants, governed the sensitivity level of cultivars towards SAR stress. Further, findings also contribute to bridging the knowledge gap regarding the responses of tropical and subtropical crops to acid rain.