Following the Photons Route

Multiple-pathways light modulation in Pleurosigma strigosum bi-raphid diatom

“…In Fig. 2 a, spherical lipid droplets superimposed onto a plastid can be distinguished, with the plastid appearing brown due to the presence of the fucoxanthin pigment 45 . Plastid shape, volume, and location inside the cell can be more effectively discerned using confocal laser scanning microscopy (CLSM), enabling the three-dimensional reconstruction of plastids by exploiting chlorophyll autofluorescence emission in the red spectral range 26 , 46 , 47 (Fig.…”

“…Diatom main pigments include chlorophyll a (Chl-a), chlorophyll c (Chl-c) (both involved in light harvesting for photosynthesis), and carotenoids (fucoxanthin, -carotene and the xanthophylls - diatoxanthin and diadinoxanthin), and in high radiation conditions a minor contribution of violaxanthin, antheraxanthin, and zeaxanthin can be detected 61 . Carotenoids are mostly implicated in photoprotection, with the exception of fucoxanthin, which transfers excitation energy very efficiently to Chl-a and plays a major role in light-harvesting complexes 45 , 62 . Chl-c is characterized by a strong blue absorption band and a weaker band in the red region (more pronounced in Chl-a, which also absorbs in the violet-blue spectral range).…”

“…Thus, the photoluminescence emission of P. strigosum frustules after UV-blue excitation entirely falls within the absorption spectra of the main diatom pigments. In clear oceanic waters, UV-violet-blue radiation is able to reach depths down to several tens of meters (in particular 60–70 m for UV-B 45 , 65 ). It is likely that blue and green radiation emitted isotropically after UV-blue excitation is partially coupled to diatom frustule and, ultimately, partially transferred to plastids 23 .…”