Exogenously applied putrescine regulates aluminium [al (III)] stress in maize (Zea mays L.): Physiological and metabolic implications

In this study, we investigated the role of exogenous application of putrescine (Put) for alleviation of Al (III) stress responses in maize seedlings. In presence of Put, the growth and biomass improved substantially in Al (III) stressed seedlings as compared to Al (III) alone. The production of hydrogen peroxide (H₂O₂) and superoxide radical (O₂^•-) were significantly restrained in during Al (III) stress in Put supplemented seedlings. The malondialdehyde (MDA) production was significantly controlled during Al (III) stress by Put supplementation as compared to the seedlings under Al (III) stress alone. The histochemical analysis showed variation in staining intensities of diaminobenzidine (DAB) and nitoroblue tetrazolium (NBT) salt to detect the presence of H₂O₂ and O₂^•- respectively, reflected strong role of Put in regulation of reactive oxygen species (ROS) production. The staining of roots with Schiff's reagent and Evans blue dye to detect lipid peroxidation and loss of plasma membrane integrity showed that Put controls the lipid peroxidation and maintains the integrity of the plasma membrane during Al (III) stress. The proton (¹H) nuclear magnetic resonance (NMR) analysis of methanolic extracts of root and shoot of maize seedlings under Al (III) stress in presence or absence of Put showed considerable disparity in terms of metabolic profiles, which include amino acids, sugars, carbohydrates, organic acids and several aliphatic and aromatic compounds. The present study exhibited the potential role of Put for mitigation of Al (III) stress by enhancing growth, regulating ROS production, reducing oxidative stress, improving antioxidant metabolism and maintaining the metabolic pool.