LAUSR

The present study was undertaken to investigate the role of potassium nitrate in the modulation of phenolic metabolism and glutathione detoxification pathway in contrasting maize genotypes, with differential response towards waterlogging stress. Waterlogging led to a higher increase in the peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, tyrosine ammonia lyase, glutathione-S-transferase, and glutathione peroxidase activities in seedlings of the tolerant genotype, I 172 as compared to the susceptible one, LM 11. Acid and alkaline protease activities were increased in roots and shoots of both the genotypes, though, I 172 seedlings showed lower protease activity than LM 11, under stress conditions. The contents of phenols, flavonoids, ortho-dihydroxyphenols and reduced glutathione were increased in seedlings of both the genotypes. The content of H2O2 and MDA were higher in LM 11 seedlings, under stress conditions. Foliar application of KNO3 further increased the peroxidase, polyphenol oxidase, phenylalanine ammonia lyase and tyrosine ammonia lyase activities in roots and shoots of both the genotypes with a parallel increase in the content of phenolic compounds. It reduced glutathione-S-transferase, glutathione peroxidase and protease activities in roots and shoots of waterlogged seedlings of both the genotypes. With the foliar treatment of potassium nitrate, the contents of GSH, H2O2 and MDA decreased in roots and shoots of I 172 seedlings at both the growth stages. It may be suggested that both K+ and $${\text{NO}}_{3}^{ - }$$ ions have a significant role in improving the phenolic metabolism and glutathione detoxification pathway leading to the enhanced tolerance of maize towards waterlogging stress.