Xanthophyll cycles in the juniper haircap moss (Polytrichum juniperinum) and Antarctic hair grass (Deschampsia antarctica) on Livingston Island (South Shetland Islands, Maritime Antarctica)

Abstract The summer climate in Maritime Antarctica is characterised by high humidity and cloudiness with slightly above zero temperatures. Under such conditions, photosynthetic activity temperature-limited plant communities are formed a few species. These conditions could prevent the operation of photoprotective xanthophyll (VAZ) cycle as low irradiance reduces excess energy temperatures limit enzyme activity. VAZ regulates dissipation absorbed light heat, which main mechanism photoprotection plants. To test whether this operates dynamically Antarctic communities, we pigment dynamics under natural field two representative species: moss Polytrichum juniperinum grass Deschampsia antarctica . Pigment analyses revealed that total pool was upper range values reported for most species, suggesting they exposed to degree environmental stress. Despite cloudiness, there strong conversion violaxanthin (V) zeaxanthin (Z) during daytime. Conversely, dark-induced enzymatic epoxidation back V not limited nocturnal In contrast plants from other cold ecosystems, did find any evidence overnight retention Z or sustained reductions photochemical efficiency. results interest modelling, remote sensing upscaling responses vegetation challenges.