Structural and Functional Alterations in Spirulina Platensis Photosynthetic Apparatus by UV-B Irradiation

Abstract

Ultraviolet (UV)B irradiation which rises on the earth’s surface due to depletion of ozone layer (1), affects the photosynthetic process at multiple sites (2). Several workers have studied the effects of UV-B radiation on structure and function of photosystems in cyanobacteria (3). The cyanobacterial thylakoids possess two distict pigment protein complexs, the photosystem (PS)I and PSH which catalyze electron transport from H2O to NADP+. The reaction centre (RC) of PSII gets light energy from phycobilisomes (PBS). In cyanobacteria, the PBS are the light harvesting antenna complexes that absorb light and transfer to RC of PSII. The PHI has been shown to be the primary target of UV-B induced damage (2). Besides, it has now been shown that the cyanobacterial PBS are also highly susceptible to UV-B damage (4). Hence, we have investigated the effect of low to moderate intensity (1.9 mW m−2) of UV-B (280–320 nm) exposure of intact cells on the thylakoid membranes of the cyanobacterium, Spirulina plantesis. Here, we present the profile of changes in thylakoid membrane characteristics by 9h long UV-B exposure to Spirulina cells.