TYPE Original Research PUBLISHED 11 October 2022 DOI 10.3389/fpls.2022.987746 OPEN ACCESS EDITED BY Iftikhar Ali, Institute of Genetics and Developmental Biology (CAS), China REVIEWED BY Adalberto Benavides-Mendoza, Universidad Autónoma Agraria Antonio Narro, Mexico Anis Ali Shah, University of Education Lahore, Pakistan Marian Brestic, Slovak University of Agriculture, Slovakia *CORRESPONDENCE Parvaiz Ahmad parvaizbot@yahoo.com Bilal Ahmad bilalbhat712@gmail.com SPECIALTY SECTION This article was submitted to Plant Abiotic Stress, a section of the journal Frontiers in Plant Science RECEIVED 06 July 2022 ACCEPTED 02 August 2022 PUBLISHED 11 October 2022 CITATION Ahmad B, Dar TA, Khan MMA, Ahmad A, Rinklebe J, Chen Y and Ahmad P (2022) Oligochitosan fortifies antioxidative and photosynthetic metabolism and enhances secondary metabolite accumulation in arsenic-stressed peppermint. Front. Plant Sci. 13:987746. doi: 10.3389/fpls.2022.987746 COPYRIGHT © 2022 Ahmad, Dar, Khan, Ahmad, Rinklebe, Chen and Ahmad. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Oligochitosan fortifies antioxidative and photosynthetic metabolism and enhances secondary metabolite accumulation in arsenic-stressed peppermint Bilal Ahmad 1,2 *, Tariq Ahmad Dar 1,2 , M. Masroor A. Khan 1 , Ajaz Ahmad 3 , Jörg Rinklebe 4,5 , Yinglong Chen 6 and Parvaiz Ahmad 7 * 1 Department of Botany, Aligarh Muslim University, Aligarh, India, 2 Department of Botany, Government Degree College for Women, University of Kashmir, Pulwama, India, 3 Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia, 4 Laboratory of Soil- and Groundwater-Management, School of Architecture and Civil Engineering, Institute of Soil Engineering, Waste- and Water Science, University of Wuppertal, Wuppertal, Germany, 5 International Research Centre of Nanotechnology for Himalayan Sustainability (IRCNHS), Shoolini University, Solan, India, 6 The UWA Institute of Agriculture, and School of Agriculture and Environment, The University of Western Australia, Perth, WA, Australia, 7 Department of Botany, Jammu and Kashmir, India The current study was designed to investigate whether application of irradiated chitosan (ICn), a recently established plant growth promoter, can prove effective in alleviating arsenic (As) stress in peppermint, a medicinally important plant. This study investigated how foliar application of ICn alleviated As toxicity in peppermint (Mentha piperita L.). Peppermint plants were treated with ICn (80 mg L −1 ) alone or in combination with As (10, 20, or 40 mg kg −1 of soil, as Na 2 HAsO 4 ·7H 2 O) 40 days after transplantation (DAT), and effects on the growth, photosynthesis, and antioxidants were assessed at 150 DAT as stress severely decreases plant growth, affects photosynthesis, and alters enzymatic (ascorbate peroxidase, superoxide dismutase) and non- enzymatic (glutathione) antioxidants. When applied at 40 mg kg −1 , ICn significantly decreased the content of essential oil (EO) and total phenols in peppermint by 13.8 and 16.0%, respectively, and decreased phenylalanine ammonia lyase (PAL) and deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) activities by 12.8 and 14.6%, respectively. Application of ICn mitigated the disadvantageous effects caused by As toxicity in peppermint by enhancing activities of antioxidative enzymes and photosynthesis and increased accretion of secondary metabolism products (EOs and phenols). An enhancement of total phenols (increased by 17.3%) and EOs (36.4%) is endorsed to ICn-stimulated enhancement in the activities of PAL and DXR (65.9 and 28.9%, respectively) in comparison to the control. To conclude, this study demonstrated that foliar application of ICn (80 mgL −1 ) effectively promoted the growth and physiology of peppermint and eliminated As-induced Frontiers in Plant Science 01 frontiersin.org