Oligomers of restructured-carrageenan impart resilience towards nickel-triggered pernicious outcomes in Mentha arvensis L.

Abstract

Radiation degradation occurs through ionizing radiations, an eco-friendly, effective, simple and single-step degradation process in which the degraded products are structurally modified (chemical modification). Nickel (Ni) manifests beneficial effects at minimal concentrations and becomes toxic at higher concentrations, thereby affecting the yield, growth and development of plants. Therefore, the present study was conducted to explore the role of structurally-modified carrageenan in imparting resilience towards nickel-triggered phytotoxicity in Mentha arvensis L. and to prove the structure-function relationship of irradiated carrageenan (ICA). The various treatments applied through foliage to the Mentha arvensis L. plant were Control, ICA (80 mg L−1), ICA (100 mg L−1), ICA (120 mg L−1), Ni (80 mg kg−1), Ni (80 mg kg−1) + ICA (80 mg L−1), Ni (80 mg kg−1) + ICA (100 mg L−1) and Ni (80 mg kg−1) + ICA (120 mg L−1). The characterization techniques employed for analysis of carrageenan samples include scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Ultraviolet-visible spectroscopy (UV-Vis). The present study was based on growth, photosynthesis, antioxidant enzymatic activities, oxidative stress biomarkers, SEM, confocal analysis of leaves and roots, and quality and yield parameters. A significant reduction of 16.45%, 22.01%, 15.38%, and 10.15% was noticed in the values of maximum quantum yield of PSII (Fv/Fm), carbonic anhydrase (CA) enzyme activity, essential oil (EO) content, and menthol content under Ni stress (80 mg kg−1). However, the foliar supplementation of 100 mg L−1 ICA enriched the values of the said parameters by 15.15%, 22.82%, 23.63%, and 4.25%, respectively. The oxidative stress biomarkers were escalated by 47.92%, 50.95%, and 35.35% for electrolyte leakage (EL), hydrogen peroxide (H2O2) content and thiobarbituric acid reactive substances (TBARS) content in Ni-stressed plants. Although, a significant down-regulation of 46.62%, 66.97%, and 32.50% was recorded in plants grown in Ni-contaminated soil and supplemented with ICA best dose.