Abstract
Cadmium (Cd) toxicity has been a wide-spread phenomenon affecting plant metabolic functions due to excessive production
of reactive oxygen species. This study was aimed at medium supplementation of optimized levels of growth modulators viz.,
salicylic acid (SA, 500 µM), ascorbic acid (AsA, 500 µM), thiourea (TU, 400 µM) and hydrogen peroxide (H2O2, 100 µM) in
improving Cd tolerance in maize (Zea mays L. hybrid P-1543) in sand culture under net house conditions. All treatments were
applied in the growing medium by dissolving in water. Results revealed that Cd stress (1000 µM) severely reduced the shoot
and root dry mass and leaf area per plant and endogenous production of osmoprotectants (soluble sugars, free proline and
glycinebetaine), phenolic compounds (soluble phenolics, flavonoids and anthocyanins) and vitamins (ascorbic acid, niacin and
riboflavin) in shoot and root tissues indicating that Cd was highly toxic to the metabolic pathways. However, medium
supplementation of the selected growth modulators was quite effective in reversing the Cd toxicity effect. Among the medium
supplemented compounds, SA and AsA were more effective in reversing the Cd toxicity effect than TU and H2O2. Presence
of tight correlations of growth attributes with metabolites levels substantiated that medium supplementation was greatly
effective in orchestrating the endogenous metabolite levels and supporting maize growth under Cd toxicity. A greater
effectiveness of the SA, AsA and TU can be attributed to their molecular structure and physiological properties in scavenging
ROS and reducing oxidative stress. The results may have great promise and practical implications for growing maize
successfully in the marginally Cd contaminated soils.
