ABSTRACT
The main objective of this work is to briefly summarize the role of oxidative alterations depending on global changes on photosynthetic organisms. An imbalance, in the formation of reactive oxygen species (ROS) and other oxidants, whether due to an increase in the production of the oxidizing species or a decrease in the activity of the antioxidant species defines ‘oxidative stress.’ The possibility of reaching this condition strongly depends on the magnitude of the change. The imbalance in ROS production is considered as the cause of several pathological changes in photosynthetic organisms, like photoinhibition, pigment bleaching, hypersensitive response against an invading pathogen, and plant tumour formation. However, when plants are exposed to abiotic or biotic agents, a low-level stress is induced. Thus, plant tolerance mechanisms could be triggered, and the environmental challenge can lead to protection against a subsequent high-level stress. The changes in climate are important factors to produce alterations in the normal physiology of plant growth. This brief summary comments on the effect of selected global changes, such as temperature, UV radiation, and salinity stress and metal contamination on the oxidative balance in the photosynthetic organisms. Even though, the overall contribution of these effects strongly depends on the studied system and on the magnitude of the challenge, it is now widely accepted that naturally triggered increases in the steady state concentration of reactive species, such as eustress, could be even beneficial to the survival of the species when exposed to further insults. However, when the antioxidant capacity is overwhelmed, cellular damage could be the consequence.
