Response of Native and Non-native to Subarctic Plant Species to Continuous Illumination by Natural and Artificial Light

The study addressed the following questions: How does continuous lighting (CL) im-pact plant physiology, photosynthetic and stress response? Does the impact of CL de-pend on the source of light and other environmental factors (natural vs artificial)? Do responses to CL differ for native and non-native plant species in the Subarctic and, if differences exist, what physiological reasons might they be associated with? Experi-ments were conducted with three native to Subarctic (Geranium sylvaticum L., Geum rivale L., Potentilla erecta (L.) Raeusch.) and three non-native plant species (Geranium himalayense Klotzsch, Geum coccineum Sibth. & Sm., Potentilla atrosanguinea Loddiges ex D. Don) introduced in Polar-Alpine Botanic Garden (KPABG, 67°38′N). Obtained re-sults have shown that plants lack specific mechanisms of tolerance to CL. Protective responses are non-specific and induced by developing photo-oxidative stress. In cli-mate chambers under constant environmental conditions artificial CL causes leaf inju-ries due to oxidative stress, the main cause of which is circadian asynchrony. In nature plants are not photodamaged during the polar day as endogenous rhythms are main-tained due to daily fluctuations of several environmental factors (light intensity, spec-tral distribution, temperature and air humidity). The obtained data show that among possible non-specific protective mechanisms, plants use flavonoids to neutralize excess ROS generated under CL. In local subarctic plants, their photoprotective role is signif-icantly higher than in non-native introduced plant species.