Coastal zones, especially littoral areas, serve as interfaces for land–sea interactions and are characterized by periodic alternation of high and low tides, thereby creating extreme habitat conditions for plant communities. The regular short-term submergence of littoral plants during high tide followed by recovery and reoxygenation during low tide requires an efficient antioxidant defense system that prevents or minimizes the accumulation of reactive oxygen species (ROS) at different stages of the tidal cycle (TC). In the present study, the activity of key antioxidant enzymes—superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)—was examined in the leaves of three dominant halophyte species (Triglochin maritima L., Plantago maritima L., Lysimachia maritima (L.) Galasso, Banfi & Soldano) at different stages of the tidal cycle (TC) in the littoral and supralittoral zones of the White Sea. The results indicate stable activity levels of SOD, CAT, and POD in the leaves of T. maritima, which employs the LOES strategy during both high and low tides in the littoral zone. In P. maritima and L. maritima, characterized by the LOQS strategy, the activity of the aforementioned enzymes in leaves decreased during high tide and increased during low tide in the littoral zone, attaining levels comparable to those of supralittoral plants. These differences are linked to the structural-functional and metabolic adaptations of littoral species directed toward maintaining the efficiency of photosynthesis and respiration under tidal cycle conditions.
Gulyaeva et al. (Tue,) studied this question.