Concomitant application of depolymerized chitosan and GA3 modulates photosynthesis, essential oil and menthol production in peppermint (Mentha piperita L.)

Radiolytic degradation of natural polysaccharides like chitosan into small oligomers and application of these as aqueous solutions to plants is a novel and recent approach towards increasing the yield of plants. Plant growth regulators, known for their growth stimulating and terpenoid biosynthetic activities also constitute a good choice for increasing the content of economically important by-products in these plants. Keeping in view the above, a pot experiment was devised with the aim to study whether foliar application of gibberellic acid (GA(3)) and irradiated chitosan (IC) could enhance essential oil (EO) content and composition, growth and biochemical attributes of Peppermint. The treatments included: a water sprayed absolute control (de-ionised water), Acetic acid control (0.03% acetic acid), (10 mg L-1) GA(3), (90 mg L-1) irradiated chitosan and combination of both i.e, GA(3) + IC. Compared to control, the combined treatment enhanced most of the parameters significantly. It increased essential oil (EO) content by 27.9%, EO yield by 61.29%, menthol content by 15.4% and menthone content by 5.85%. However, the menthyl acetate content was reduced by 1.46%.