Influence of linoleic acid on growth, oxidative stress and photosynthesis of the cyanobacterium Cylindrospermopsis raciborskii

In this study, the effects of linoleic acid on the growth, photosynthetic activities and oxidative system of the invasive cyanobacterium Cylindrospermopsis raciborskii were investigated. The results indicated that linoleic acid decreased the growth rate and chlorophyll a concentration in C. raciborskii after 48 h incubation. The maximum photochemical efficiency (F-v/F-m) of photosystem II (PSII) and maximum relative electron transport rate (ETRmax) decreased significantly at concentrations higher than 1mgL(-1). However, non-photochemical quenching (NPQ) significantly increased when cultured at concentrations of 0.5, 1, 2 and 4mgL(-1). PSII electron transfer rate and chlorophyll a fluorescence transients appeared to be affected after the cells were exposed to higher concentrations of linoleic acid; the density of the reaction centres (RCs), quantum energy flux ratios and the performance index on absorption basis decreased, but absorption flux per RC and dissipated energy flux per RC increased. Malondialdehyde content, superoxide dismutase and catalase activities were enhanced when exposed to 2 and 4mgL(-1) of linoleic acid. This suggests that the blockage of electron transport on the donor and acceptor sides of PSII is the mechanism responsible for the toxicity of linoleic acid in PSII of C. raciborskii.