Kinetin Alleviates UV-B-Induced Damage in Solanum lycopersicum: Implications of Phenolics and Antioxidants

Abstract

Cytokinins, a class of plant growth regulators, are known to regulate several plant developmental processes and may play a significant role in protecting them against abiotic stresses. Thus, this study was focused on the effect of kinetin (KN, 10 µM) treatment on phenylpropanoid pathway: PAL activity, phenolics, flavonoids, and anthocyanins contents, and oxidative stress biomarkers, antioxidant potential, and growth in tomato seedlings exposed to UV-B (UV-B1, ambient + 1.2 kJ m−2 day−1 and UV-B2, ambient + 2.4 kJ m−2 day−1) stress. UV-B exposure to KN untreated seedlings caused substantial increase in reactive oxygen species contents: superoxide radical and hydrogen peroxide (H2O2), and oxidative damage biomarkers: lipid peroxidation and electrolyte leakage in a dose-dependent manner, despite increased antioxidant potential: super oxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione-S-transferase (GST) activity, and radical scavenging capacity (DPPH activity), PAL activity, total phenolics, flavonoids and anthocyanins contents. The seedlings pre-treated with KN and subsequently exposed to UV-B exhibited substantial increase (i) in antioxidant potential: SOD, POD, CAT and GST activity, and DPPH activity and (ii) PAL activity which led to a further rise in total phenolics, UV-B screening pigments (flavonoids) and anthocyanins and hence, significant lowering in oxidative stress biomarkers was noticed. The overall results show that KN pre-treatment significantly alleviated UV-B-induced damaging effects in tomato seedlings by regulating phenolics and antioxidants.