Oxalic Acid Mitigates Cadmium Toxicity in Cicer arietinum L. Germinating Seeds by Maintaining the Cellular Redox Homeostasis

The present study aimed to investigate the potential protective role of oxalic acid (OA) against Cadmium (Cd) toxicity. Chickpea (Cicer arietinum L.) seeds were exposed to 200 µM Cd stress for 6 days or to co-treatment with 200 µM Cd + 100 µM OA for 3 days following to 3-day Cd stress. The application of OA ameliorated the growth of both roots and shoots of Cd-treated seedlings. This effect was mediated by the restriction of Cd accumulation in plant tissues. Besides, malondialdehyde (MDA) and carbonyl group contents decreased in OA-treated seedlings, suggesting that OA reversed the Cd-induced oxidative stress and its detrimental effect on cell membrane integrity. These results were further confirmed by the reduction by 2- and 1.7-fold of hydrogen peroxide (H₂O₂) accrual in roots and shoots, respectively, when compared to Cd-challenged seedlings. Moreover, OA corrected the Cd-imposed imbalance of the glutathione redox state, mainly via the restoration of the glutathione pool. This achievement seems to be the result of the modulation of glutathione peroxidase (GPX) and glutathione reductase (GR) activities. Likewise, OA counteracted the adverse effect of Cd on nicotinamides redox state reflected by the restoration of the balance between oxidized [NAD(P)] and reduced [NAD(P)H] forms. Taken together, our results suggest that the exogenous supply of OA to germinating seeds can be a promising alternative to improve plant tolerance to heavy metal stress.