EFFECT OF FOLIAR SPRAY OF ASCORBIC ACID ON NODULATION, GAS EXCHANGE ATTRIBUTES AND MINERAL ION CONTENTS OF PISUM SATIVUM UNDER ZINC STRESS

Abstract

Heavy metal toxicity is one of the major abiotic stresses leading to hazardous effects in plants. Ascorbic acid is regarded as one of the most effective antioxidants present in plants. A pot experiment was conducted to determine the effect of foliar spray of ascorbic acid on nodulation, gas exchange attributes, and mineral ion contents of pea (Pisum sativum L.) cultivars under zinc stress. Seeds of two pea cultivars cv. 2001-40 and cv. Meteor were sown in pots following a completely randomized design (CRD) with three replicates. Treatments of ZnSO4.7H2O (5 and 10 mg kg-1) were applied through the rooting medium whereas ascorbic acid (5 ppm and 10 ppm) as foliar sprays after three weeks of germination. Results revealed that zinc stress reduced the growth, gas exchange attributes, potassium and calcium contents of roots and shoots of both the pea cultivars. However, foliar spray of ascorbic acid counteracted the adverse effect of zinc stress on the growth of both pea cultivars. The application of 10 mg kg-1 ascorbic acid proved to be more effective in inducing zinc stress tolerance as compared to other levels. Growth and gas exchange attributes of zinc-stressed plants of both cultivars were also enhanced due to foliar applied ascorbic acid which was positively associated with mineral ion contents. Overall, foliar-applied ascorbic acid ameliorated the adverse effect of zinc stress on nodulation and growth attributes of pea cultivars.