Plants are exposed to different types of environmental stressors throughout
the different developmental stages. Reactive oxygen species (ROS) are found to play
key roles in the maintenance of normal plant growth and improving their ability of
stress tolerance. ROS as a secondary messenger performs crucial cellular functions,
including the proliferation of cells, apoptosis, and necrosis. Both the external
environmental factors and intrinsic genetic programs regulate the morphogenesis of
plants. ROS are also considered as by-products of the aerobic metabolism of the plant
and are formed in certain cellular compartments like mitochondria, chloroplasts, and
peroxisomes. Plants form a huge number of ROS species under unfavorable
circumstances that are involved in the regulation of different processes, including
programmed cell death, pathogen defense, and stomatal behavior. These reactions often
exert irreversible or profound effects on the development of organs and tissues, leading
to abnormal death or plant growth. Several molecular approaches to understand the
signaling and metabolism of ROS have opened novel avenues in comprehending its
key role in abiotic stress. Plants possess their own enzymatic and non-enzymatic
antioxidant defense system to encounter ROS. The interconnecting activities of these
defensive antioxidants reduce oxidative load and regulate the detoxification of ROS in
plants. This book chapter will highlight the importance of ROS metabolism and the
role of the antioxidant defense mechanism of plants in combating the deleterious effect
of oxidative stress under stressful conditions.
Keywords: Antioxidant defense system, Detoxification, Pathogen, Plant reactive
oxygen species.
