Photosynthetically active radiation interacts with UVR during photoinhibition and repair in the cyanobacterium Arthrospira platensis (Cyanophyceae)

Abstract

:Cultures of Arthrospira platensis were exposed to ultraviolet (UV, 280–400 nm, 7.9 W m−2) radiation alone, or ultraviolet radiation (UVR) supplemented with different levels of photosynthetically active radiation (PAR, 400–700 nm). Cells showed high primary susceptibility to photoinactivation of Photosystem II (PSII) when exposed to UVR alone, while UVR supplemented with PAR led to the enhancement of the PSII activity. Both UVR and PAR initiated the protein repair; the highest D1 protein amount was shown under the radiation treatment of UVR plus 2.6 W m−2 PAR, which was consistent with the highest PSII activity. We concluded that PAR interacted with UVR, resulting in synergistically enhanced protein repair capacity but the extent of the relative protective effect depended on the irradiance level of PAR and the total solar radiation that cell received.