Effects of BAP and zinc nanoparticles on in vitro growth and antioxidant activity of Solanum tuberosum L.

Plant tissue culture provides a rapid method for producing disease free and genetically identical plant material. Plant growth regulators (PGRs), particularly cytokinins such as 6-benzylaminopurine (BAP), play an important role in in vitro morphogenesis. Besides PGRs, nanoparticles have recently emerged as promising supplements for enhancing plant growth and antioxidant defense mechanism. The present study evaluated the combined effects of BAP and zinc nanoparticles (ZnNPs) on shoot proliferation and antioxidant enzyme activity in Solanum tuberosum L. under in vitro conditions. Explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations of BAP (1, 1.5 and 2 mg/L) and ZnNPs (10, 20 and 30ppm) either alone or in combination with each other. The highest average number of shoots per explant (6.67) was observed at 1 mg/L BAP, although shoot length was decreased as compared to control (5.87%). A low concentration of ZnNPs improved growth attributes, resulting in 5.88%, 25.00% and 36.36% enhancement in shoots per explant, shoot length and shoot fresh weight as compared to control, respectively. However, higher concentrations (30 ppm) of ZnNPs caused a decline in growth parameters. Biochemical analysis revealed that BAP (1 mg/L) enhanced antioxidant enzymes activities including peroxidase (POX), phenylalanine ammonium lyase (PAL), polyphenol oxidase (PPO) by 0.563, 0.039 and 0.317 unit/mg of protein, respectively, compared to control. ZnNPs (10ppm) further enhanced the activity of POX, PAL and PPO by 18.42%, 14.31% and 14.86% with respect to only BAP treated plants. Combined application of BAP and ZnNPs at low concentrations enhanced all the growth and biochemical parameters, while higher concentrations showed an inhibitory effect on these parameters.