Abstract
Snow algae and green algae living in aeroterrestrial habitats are ideal objects to study adaptation to high light irradiation. Here, we used a detailed description of the spectral properties as a proxy for photo-acclimation/protection in snow algae (Chlamydomonas nivalis, Chlainomonas sp. and Chloromonas sp.) and charophyte green algae (Zygnema sp., Zygogonium ericetorum and Klebsormidium crenulatum). The hyperspectral microscopic mapping and imaging technique allowed us to acquire total absorption spectra of these microalgae in the waveband of 400–900nm. Particularly in Chlamydomonas nivalis and Chlainomonas sp., a high absorbance between 400–550nm was observed, due to naturally occurring secondary carotenoids; in Chloromonas sp. and in the charopyhte algae this high absorbance was missing, the latter being close relatives to land plants. To investigate if cellular water loss has an influence on the spectral properties, the cells were plasmolysed in sorbitol or desiccated at ambient air. While in snow algae, these treatments did hardly change the spectral properties, in the charopyhte algae the condensation of the cytoplasm and plastids increased the absorbance in the lower waveband of 400–500nm. These changes might be ecologically relevant and photoprotective, as aeroterrestrial algae are naturally exposed to occasional water limitation, leading to desiccation, which are conditions usually occurring together with higher irradiation.
Highlights
Snow algae and aeroterrestrial algae are naturally exposed to high photosynthetically active radiation (PAR) as well as ultra violet (UV) radiation, e.g. [1,2,3]
The hyperspectral imaging technique (PARISS®) used is attractive because it provides a spatial analysis of spectral information from live specimen of single-celled algae
This is innovative in the sense that conventional techniques either (1) characterize the ultrastructure of fixed cells, use dyes to locate certain cellular compartments or (2) characterize spectra from cells after pigment extraction and spectral analysis from the extract
Summary
Snow algae and aeroterrestrial algae are naturally exposed to high photosynthetically active radiation (PAR) as well as ultra violet (UV) radiation, e.g. [1,2,3]. As for snow algae, secondary pigments like the carotenoid astaxanthin, which is responsible for the red color of the spores (‘red snow’), has substantial protecting capacities for the photosynthetic apparatus e.g. Pigment composition in red snow algae (Chloromonas nivalis and other Chlamydomonadaceae) and green snow algae (mostly containing Microglena sp.) collected from Svalbard (Norway) showed that primary carotenoids attributed only for 4% of the total pigments whereas the total secondary carotenoids comprised 92% of the pigments [12]. Snow algal spores of Chlamydomonas nivalis [1], Chlainomonas [10] or Chloromonas nivalis [14] are occasionally surrounded with organic and inorganic matter from the immediate surrounding environment, likely to prevent excessive irradiation in the snowfields
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More From: Journal of Photochemistry and Photobiology B: Biology
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