Phytoprotectants in Action: Shielding Plants from Oxidative Damage under Thermal Extremes and Flooding Stress

Abstract

Waterlogging (WL) and extreme temperatures are major abiotic stresses that threaten agricultural productivity. High and low temperatures impair photosynthesis, reduce enzyme activity and destabilize membranes, whereas WL causes hypoxia, nutrient imbalance and metabolic disorder. Both stresses lead to excessive build-up of reactive oxygen species (ROS), and the resulting oxidative stress damages lipids, proteins and nucleic acids, reducing plant growth and yield. Reactive oxygen species are natural byproducts of plant metabolism, but their rapid increase during stress disturbs redox balance, destabilizes cellular structure and can cause irreversible damage or even plant death. Naturally occurring or synthetic phytoprotectants applied exogenously have therefore been studied extensively for their ability to improve plant tolerance. These compounds include antioxidants, osmoprotectants, phytohormones, biostimulants and plant extracts, and they increase stress resistance by enhancing enzymatic and non-enzymatic antioxidant defense, stabilizing membranes, regulating stress-responsive genes and maintaining osmotic balance. In temperature-stressed plants, compounds such as salicylic acid, ascorbic acid and brassinosteroids alleviate heat- or cold-induced oxidative damage, while under WL, ethylene synthesis inhibitors, polyamines and signaling molecules improve redox balance and sustain metabolism. This review summarizes recent evidence on how phytoprotectants mitigate oxidative stress under extreme temperatures and WL and discusses their potential for climate-resilient crop production. J. Bangladesh Acad. Sci. 50(3); 347–367: September 2026