This paper describes the first study of the diatom assemblages in caves in the Czech Republic. The study focused on subaeric habitats: rock faces within caves, walls at cave entrances and “lampflora” assemblages, in three cave systems, Mladeč, Javoříčko and Zbrašov, all in central Moravia. The morphological and cytological variability, ecology and life strategies of diatoms were studied in fresh samples, in Naphrax preparations, in cultures grown on agar plates and in monoclonal cultures. A total of 22 diatom species was identified, mostly aerophytic species and tolerant of low light intensities. Luticola and Diadesmis species complexes are discussed. Taxa D. gallica and L. paramutica var. binodis are new for the Czech Republic. Sexual reproduction was observed in L. mutica and Orthoseira roeseana.
Monoclonal cultures of the aerophytic cave diatom Luticola dismutica were studied and its frustule morphology, cytology and reproduction recorded. Luticola dismutica is a laterally asymmetrical, monoplastidic pennate diatom with imposed chloroplast division and nuclear behaviour of type 1.A sensu Mann & Stickle. Clones of L. dismutica decreased in cell size in culture until they have reached the sexual size range. Homothallic sexual reproduction and auxosporulation (type IB1a auxosporulation sensu Geitler) were induced in four sexualized clones. Gametangia paired via the girdle, two isogametes were formed per gametangium and hence two zygotes were produced per pair of gametangia. No surviving superfluous nuclei were observed in the gamete and zygote stages and no unfused haploid nuclei were seen in the auxospore stage; zygotes and expanded auxospores had only one nucleus. Auxospores expanded perpendicular to the apical axis of gametangia. Expanded auxospores and initial cells had a swollen central part, the linear-lanceolate outline shape of the vegetative valves was restored during the first divisions of the post-initial cells. Initial cells left the perizonium by a route unique to pennate diatoms, through a transverse rupture of the perizonium. The key cytological and reproductive characteristics reviewed in this paper indicate, that Luticola is more closely related to Placoneis and Dickieia, than to Navicula sensu stricto.
The sensitivity of phytoplankton species for hydrogen peroxide (H2O2) was analyzed by pulse amplitude modulated (PAM) fluorometry. The inhibition of photosynthesis was more severe in five tested cyanobacterial species than in three green algal species and one diatom species. Hence the inhibitory effect of H2O2 is especially pronounced for cyanobacteria. A specific damage of the photosynthetic apparatus was demonstrated by changes in 77 K fluorescence emission spectra. Different handling of oxidative stress and different cell structure are responsible for the different susceptibility to H2O2 between cyanobacteria and other phytoplankton species. This principle may be potentially employed in the development of new agents to combat cyanobacterial bloom formation in water reservoirs. and M. Drábková ... [et al.].