Dual effects of ultraviolet radiation (UVR; 280-400 nm) on photosynthesis and stress response in cyanobacterium Synechococcus elongatus PCC 7942.

UNLABELLED: While the effects of ultraviolet radiation (UVR; 280-400 nm) on cyanobacterial systems have been extensively documented, the specific impact on photochemical yield remains less understood. To address this gap, we investigated the physiological performance of the model cyanobacterium Synechococcus elongatus PCC 7942 under UVR exposure. Employing Pulse Amplitude Modulation (PAM) fluorometry, a non-invasive technique, we assessed the photochemical efficiency of Photosystem II (PSII). Our data not only corroborate previous findings but also provide novel insights into the potential of UVR to enhance photosynthetic electron transport rates in Synechococcus elongatus PCC 7942. This study examined the combined effects of photosynthetically active radiation (PAR; 400-700 nm) and UVR on the growth and various physiological parameters of this cyanobacterium. Notably, while PAR + UVR negatively influenced growth, it did not compromise overall fitness. The observed enhancement in carotenoid production, modulation of pigment ratios, and maintenance of cellular morphology suggest the activation of acclimatization mechanisms in response to the combined light stress. Despite initial declines in photosynthetic performance, the remarkable recovery and resilience of Synechococcus elongatus PCC 7942 over time underscore its robustness. Consequently, these findings illuminate the resistance mechanisms of this commercially important cyanobacterium to changing light environments, highlighting the dual role of UVR as both an environmental stressor and a trigger for protective physiological responses. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-026-01797-1.