Alleviation of Copper-Induced Stress in Pea (Pisum sativum L.) through Foliar Application of Gibberellic Acid

SIMPLE SUMMARY: Phytohormones are key regulators of several stages of plant growth and development as well as provide the regulatory response against various heavy metals stresses by mediating physio-morphological responses and enzymatic activities. The current study evaluated the effects of gibberellic acid (GA(3)) foliar applications on the performance of pea grown either in Cu-contaminated (Cu+) and non-contaminated (Cu−) soil. GA(3) was applied exogenously (0, 10, 50, and 100 mg·L(−1)) on 15-days-old plants, and the results show that the increasing concentration of GA(3) buffered the phytotoxic effects of Cu, coupled with an increase in plant growth and physiological variables. The results also showed that foliar-applied GA(3) up to 100 mg·L(−1) alleviated the oxidative stress, as inferred from the lower concentrations of malondialdehyde (MDA) and H(2)O(2), which mirrored the increased activity of antioxidant enzymes, i.e., superoxide dismutase, peroxidase, and catalase. In addition, enhanced growth, physiology, and enzymatic activities were also observed in pea plants sprayed with GA(3) up to 100 mg·L(−1) in Cu− soil. Overall, the foliar application of GA(3) boosted phytoextraction of Cu from the soil and alleviated the oxidative stress in pea plants grown in Cu-polluted soil. ABSTRACT: Copper (Cu) is an essential metal for plants. However, its excess in soil can adversely affect plant metabolism. The current study evaluated the effects of gibberellic acid (GA(3)) foliar applications on the performance of pea plants grown either in Cu-contaminated (Cu+) and non-contaminated (Cu−) soil. GA(3) was sprayed (0, 10, 50, and 100 mg·L(−1)) on 15-days-old plants. The results showed that the increasing concentration of GA(3) buffered the phytotoxic effects of Cu and enhanced plant growth, photosynthesis, and leaf chlorophyll content. Foliar-sprayed GA(3) up to 100 mg·L(−1) alleviated the oxidative stress, as inferred from the lower concentrations of MDA and H(2)O(2) (33.3 µmol·g(−1) and 182 µmol·g(−1), respectively), and boosted the activity of superoxide dismutase (64.4 U·g(−1)·FW), peroxidase (122.7 U·g(−1)·FW), and catalase (226.3 U·g(−1)·FW). Interestingly, GA(3) promoted Cu accumulation in different plant parts when compared to untreated plants, likely due to increased photosynthetic and transpiration rates. Overall, foliar application of GA(3) promoted phytoextraction of Cu and alleviated the oxidative stress in pea plants grown in Cu+ soil.