The effects of paclobutrazol on enhancing tolerance of Plantago major L. to cadmium stress in vitro

Abstract

The plant tissue culture technique has enabled us to study the tolerance of cells, tissues, and plant organs and cultures to different stresses that plants suffer from. The in vitro culture facilitates the ability to stimulate the production of secondary metabolites. The present study investigated the influence of paclobutrazol (PBZ) pre-treatment on the growth, physiological, morphological, biochemical traits, and phenolic compounds production in callus cultures of Plantago major L. in a medium containing different concentrations of cadmium. The callus was cultured in a Murashige and Skoog (MS) medium with different concentrations of cadmium (0, 50, 100, 150, and 200 µM), with a PBZ concentration of 0 and 2 mg l-1. A factorial experiment based on a completely randomized design (CRD) was performed in triplicate. The results of the growth of the callus culture were obtained after 28 days. The increasing concentrations of cadmium were found to have a negative effect on some traits such as fresh weight (FW), dry weight (DW), browning intensity (BI), tolerance index (TI), electrolyte leakage (EL), and membrane stability index (MSI). The PBZ treatment reduced the effects of cadmium levels through the decrease in malondialdehyde (MDA), and hydrogen peroxide (H2O2). This was caused by a significant increase in superoxide dismutase (SOD) and ascorbate peroxidase (APX). Also, there was an increase in total phenol and flavonoids content in the callus grown on the tissue cultures supporting 200 µM cadmium compared to the other levels. The PBZ pre-treatment was a significant reducing factor to produce total phenolic and flavonoids content in P. major L. callus culture under the cadmium levels.