Abstract
The lipid-producing model alga Nannochloropsis oceanica has a distinct photosynthetic machinery. This organism possesses chlorophyll a as its only chlorophyll species, and has a high ratio of PSI to PSII. This high ratio of PSI to PSII may affect the redox state of the plastoquinone pool during exposure to light, and consequently may play a role in activating photoprotection mechanisms. We utilized pulse-amplitude modulated fluorometry to investigate the redox state of the plastoquinone pool during and after bright light pulses. Our data indicate that even very intense (5910 μmol photons s-1m-2 of blue light having a wavelength of 440 nm) light pulses of 0.8 second duration are not sufficient to completely reduce the plastoquinone pool in Nannochloropsis. In order to achieve extensive reduction of the plastoquinone pool by bright light pulses, anaerobic conditions or an inhibitor of the photosynthetic electron transport chain has to be utilized. The implication of this finding for the application of the widely used saturating pulse method in algae is discussed.
Highlights
Pulse Amplitude Modulated (PAM) fluorometry has proven a valuable technique for studying the photosynthetic performance of plants and algae in situ [1, 2]
Sophisticated PAM fluorometry techniques have been developed that allow for the assessment of photosynthetic performance and for the characterization of different mechanisms that modulate chlorophyll fluorescence
We investigated if the saturation pulse methodology can be applied to the heterokont model alga Nannochloropsis
Summary
Pulse Amplitude Modulated (PAM) fluorometry has proven a valuable technique for studying the photosynthetic performance of plants and algae in situ [1, 2]. A PAM fluorometer assesses variable chlorophyll fluorescence by applying very weak measuring light pulses that ideally do not induce photosynthesis. The fluorescence induced by these low energy light pulses can be electronically isolated from the fluorescence induced by other light sources. The fluorescence signal obtained by a PAM fluorometer is interpreted and independent of applied light sources, which could include photosynthetically active light or additional saturating light pulses. Sophisticated PAM fluorometry techniques have been developed that allow for the assessment of photosynthetic performance and for the characterization of different mechanisms that modulate chlorophyll fluorescence
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