Effect of Plant hormones on phenolic content and PAL activity of peppermint under Cd. toxicity

Cadmium (Cd+2) is a potential and widespread toxic environmental pollutant that has inhibitory effects on growth, physiological, and biochemical attributes of various plant species, including medicinal plants such as Mentha piperita L. Plant signaling molecules, when applied exogenously, help to enhance/activate endogenous biosynthesis of potentially important signaling molecules and antioxidants that boost tolerance against various abiotic stresses, e.g., heavy metal stress. In this study, for the first time, investigated the effects of foliar application of salicylic acid and strigolactone on total phenol, DPPH radical scavenging activity and the activity of phenylalanine ammonia-lyase (PAL) enzyme under different concentrations of cadmium stress. The experiment was conducted using a completely randomized design with four replications. Results revealed that the foliar spraying of salicylic acid and strigolactone significantly decreased lipid peroxidation and hydrogen peroxide accumulation in peppermint leaves, indicating a reduction in cadmium toxicity. Moreover, the increase in phenolic compounds and phenylalanine ammonia-lyase (PAL) enzyme activity under the treatment of strigolactone and salicylic acid suggested an enhancement in peppermint's resistance to cadmium toxicity by improving antioxidative defense system. Enhancing antioxidant pool especially phenolic compounds accumulation is one of the most important nonenzymatic tools of plants to resist environmental stresses.

Effect of Plant hormones on phenolic content and PAL activity of peppermint under Cd. toxicity Keywords:

Peppermint , Cadmium , Oxidative stress , Salicylic acid , Strigolactone