Effect of plant growth regulators, calcium and citric acid on copper toxicity in pea seedlings

The present investigation aims to study the potential protective role of exogenous applications of gibberellin, auxin, citric acid and calcium on the growth and cellular redox state of pea (Pisum sativum L.) germinating seeds exposed to copper stress. All tested treatments alleviated the adverse effects of Cu-induced toxicity on the growth, cell viability and mobilization of nutrients from the cotyledons. This alleviation of Cu toxicity occurred by limiting heavy metal biosorption and maintaining cellular redox homeostasis. Redox balance, examined through the study of the redox state of nicotinamide couples NAD(+)/NADH and NADP(+)/NADPH appeared to be protected by the treatments. This correction was correlated to a modulation of NAD(P)H-oxidase and dehydrogenase activities, such as glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malate dehydrogenase. The present research provides evidence that supplementation of plants with gibberellin, auxin, citric acid and calcium was an effective approach for enhancing Cu tolerance in pea seedlings.