The Estonian Mycological Collections of Heinrich August Dietrich (1820–1897)

Heinrich August Dietrich was a gardener with a deep interest in mycology. He published a two-volume monograph dealing with over 1,000 fungal and fungal-like taxa, the first cryptogamic research of this kind for the Baltic region. Between 1852 and 1857, H. A. Dietrich issued nine volumes of exciccatae named Centuria Plantarum Florae Balticae cryptogamarum. The preserved eight Centuriae and additional collections from Estonia (then the Imperial Russian Baltic province, Estonian Governorate) are revised and their current status in collections is presented. As a result, a new myxomycete species for Estonia, Physarum gyrosum, and the once doubtfully-reported species, Arcyria oerstedii, are recorded, and the earliest vouchers of some endangered ascomycetes, such as Poronia punctata and Sabuloglossum arenarium, are identified in his material. The most remarkable findings among lichenized fungi are Alectoria sarmentosa, Dibaeis baeomyces, Flavoparmelia caperata, Lasallia pustulata, Nephroma laevigatum, Peltigera venosa and Ramalina calicaris, as well as the oldest Estonian specimen of Lobaria pulmonaria.

Structural evidence of diffuse growth and parenchymatous cell division in the cortex of the umbilicate lichen Lasallia pustulata

How growth is distributed within the morphologically diverse thalli of lichens is still poorly known and the anatomical mechanisms involved are not well understood. This work applies electron microscopy (SEM and TEM) to examine cell- and tissue-level events in the umbilicate thallus of Lasallia pustulata, whose pattern of expansion was the subject of a previous field study. Stacks of epinecral tissue accumulating at the thallus surface showed broadening bases and recurring rupture attributable to diffuse expansion of the living tissue below. Cortical cells, dividing anticlinally, adjoined septa to previous septa, indicating parenchymatous divisions. These observations are all consistent with previous contentions that mature, organized tissues within the thallus are capable of continued diffuse growth. They provide a developmental explanation for the morphology of the epinecral layer and suggest that anatomical characteristics may be helpful in recognizing diffuse growth patterns. Parenchymatous cell divisions, believed until recently to never occur in lichen thallus tissues, are shown to play a developmental role in the diffuse growth of the umbilicate lichen thallus.

Pigment composition, glutathione and tocopherols in green algal and cyanobacterial lichens and their response to different light treatments

This study investigated photosynthetic pigments chlorophyll a and b, carotenoids (including xanthophyll cycle pigments) and antioxidants glutathione and tocopherols contents in chloro- (Lobaria pulmonaria, Lasallia pustulata) and cyanolichens (Lobaria scrobiculata, Peltigera canina) from different habitats and of different geographical origin. Lichen thalli were treated with various levels of irradiance (from 100 to 1500 mmol m-2 s-1) for various time periods (from 20 min. to 5 h). The extent of increase of zeaxanthin content after different light treatments differed among chlorolichens, clearly distinguishing the species from light and shade habitats. Irrespective of light treatment, β-carotene content was always higher in cyanobacterial species than in green algal species. Highest canthaxanthin concentration, as well as β-carotene concentration, was found in L. scrobiculata from shade habitat. The content of total glutathione was the same in the same species from different collection sites. On the contrary, contents of a-tocopherol differed in the same species from different collection sites.

Fv/Fm acclimation to the Mediterranean summer drought in two sympatric Lasallia species from the Iberian mountains

Photosynthetic performance in lichens can vary throughout the year. We investigate the variation in the PSII quantum efficiency as a proxy for the physiological state of the photosynthetic apparatus in two umbilicate species from the genus Lasallia. Temporal variation in Fv/Fm in both species was monitored at a field site in Central Spain where both species coexist. Subsequent measurements were carried out in the laboratory after 48 h preconditioning. Both species showed clear variation during the year in PSII performance, with a marked depression in Fv/Fm during the summer. Lasallia pustulata consistently had higher Fv/Fm values than L. hispanica. Both species reached higher Fv/Fm values after 48 h of preconditioning in the laboratory and this recovery was particularly notable in the summer months. Fv/Fm was highly related to antecedent weather conditions during the two days prior to measurement.

Photobiont associations in co-occurring umbilicate lichens with contrasting modes of reproduction in coastal Norway

The identity and phylogenetic placement of photobionts associated with two lichen-forming fungi, Umbilicaria spodochroa and Lasallia pustulata were examined. These lichens commonly grow together in high abundance on coastal cliffs in Norway, Sweden and Finland. The mycobiont of U. spodochroa reproduces sexually through ascospores, and must find a suitable algal partner in the environment to re-establish the lichen symbiosis. Lasallia pustulata reproduces mainly vegetatively using symbiotic propagules (isidia) containing both symbiotic partners (photobiont and mycobiont). Based on DNA sequences of the internal transcribed spacer region (ITS) we detected seven haplotypes of the green-algal genus Trebouxia in 19 pairs of adjacent thalli of U. spodochroa and L. pustulata from five coastal localities in Norway. As expected, U. spodochroa associated with a higher diversity of photobionts (seven haplotypes) than the mostly asexually reproducing L. pustulata (four haplotypes). The latter was associated with the same haplotype in 15 of the 19 thalli sampled. Nine of the lichen pairs examined share the same algal haplotype, supporting the hypothesis that the mycobiont of U. spodochroa might associate with the photobiont ‘pirated’ from the abundant isidia produced by L. pustulata that are often scattered on the cliff surfaces. Up to six haplotypes of Trebouxia were found within a single sampling site, indicating a low level of specificity of both mycobionts for their algal partner. Most photobiont strains associated with species of Umbilicaria and Lasallia, including samples from this study, represent phylogenetically closely related taxa of Trebouxia grouped within a small number of main clades (Trebouxia sp., T. simplex/T. jamesii, and T. incrustata+T. gigantea). Three of the photobiont haplotypes were found only in U. spodochroa thalli.