Climate is the great factor that mankind has not yet managed to control. Drought, flood, high temperature, salinity and air pollution are among the major factors limiting crop productivity. The effects of various environmental stresses in plants are known to be mediated, at least partially, by an enhanced generation of reactive oxygen species (ROS). The main site of ROS production in stressed plant is chloroplast, exposed to excessive energy absorbed. ROS are highly reactive and can cause widespread damage to membranes, proteins and DNA. To prevent such damages there are a number of enzymatic processes in chloroplast to scavenge ROS. Unfortunately they are highly energetically demanding, requiring the synthesis of high concentrations of the low-molecular weight antioxidants and antioxidative enzymes. Therefore, to place less of a metabolic burden on plants, the effective regulation of the photosynthetic electron transport is crucial to avoid enhanced ROS formation under stress conditions. In Researcher recent studies the effects of short-term salt stress on the regulation of photosynthetic electron transport in Arabidopsis thaliana and its salt-tolerant close relative Thellungiella halophila has been examined. Results obtained provide the evidence for the plastid terminal oxidase (PTOX) to act as a significant electron sink from photosystem II (PSII). In salt-stressed Thellungiella, PTOX-dependent electron transport accounts for up to 30% of total linear electron flow, suggesting a major role for this pathway in protecting plants from photodamage. The aim of present project is to investigate the role and functioning of PTOX in Thellungiella halophila with the focus on the regulatory mechanism and factors that allow it to act as a sink for electron transport from PSII. Additionally, we will investigate whether Thellungiella PTOX activity can be transferred into another species and whether this has the potential to increase stress tolerance.