Nighttime warming enhances photosynthetic activity and induces changes in chloroplast membrane structure and antioxidant profile in Platycerium ferns

Global warming leads to asymmetric shifts in daily temperature, with nighttime temperatures increasing more rapidly, which may significantly impact plant physiological processes. Ferns are among the species sensitive to climate change, however their responses to rising nighttime temperatures remain poorly understood. The aim of this study was to evaluate changes in the photosynthetic apparatus and antioxidant profile of two popular ornamental fern species: Platycerium bifurcatum and Platycerium alcicorne in response to an increase in nighttime temperature to daytime levels (resulting in a 2.3 °C increase in the daily mean). The analysis included measurements of chlorophyll a fluorescence, gas exchange parameters, pigment profile, antioxidant enzyme activity, non-enzymatic antioxidant content, lipid peroxidation level and physicochemical properties of chloroplast membranes. For the first time in ferns, it was demonstrated that an elevation in nighttime temperature stimulated gross photosynthesis and increased the efficiency of photosystem II. Furthermore, an increase in chlorophyll and flavonoid content, a reduction in malondialdehyde levels (MDA), and greater chloroplast membrane elasticity was observed, particularly within galactolipids fraction. Moderate nocturnal warming may stimulate acclimation processes, improving the photosynthetic efficiency of ferns and enhancing their adaptive potential, which is relevant in the context of the predicted expansion of climate-resilient species and their role in urban ecosystems. The experiment provides a foundation for further research on the effects of long-term warming on the reproduction, growth and population dynamics of Platycerium and other fern species.