Topic
Isidium
About: Isidium is a research topic. Over the lifetime, 6 publications have been published within this topic receiving 180 citations.
Papers
TL;DR: The described transplantation technique of vegetative diaspores has proved to be very useful for the augmentation of small populations without damaging the existing thalli and it is suggested use of this method for in situ conservation of endangered lichen species.
Abstract: Development and growth of the three threatened epiphytic lichen species Sticta fuliginosa (Hoffm.) Ach., Leptogium saturninum (Dicks.) Nyl. and Menegazzia terebrata (Hoffm.) Massal. was investigated by low temperature scanning electron microscopy and macro-photography. Small cotton gauze discs acting as artificial substrata were fixed with aluminium staples on the bark of selected trees and vegetative diaspores (isidia or soredia) were transferred onto these discs. The subsequent development into small thalli of up to 3 mm length was observed within the 32-month study period. All three species produced anchoring hyphae within the first month after transplantation. Two months later 52 % of the S. fuliginosa diaspores were still on the gauze discs and after 16 months 29 % remained attached. For L. saturninum, the corresponding percentages were 46 % and 19 %, respectively. First lobes resembling adult thalli were observed after 8 to 12 months in S. fuliginosa and L. saturninum but only after 16 months in M. terebrata. All three species developed usually more than one thallus primordium (pseudomeristematic growth zone) per isidium or soredial cluster. Transplanted thallus fragments were able to fix themselves on the new substratum but in all three species large parts degenerated and fell off during the first year, particularly in S. fuliginosa. The results show that the juvenile development of the investigated species is not restricted by microclimatic factors at the study site. We therefore conclude that the juvenile development is not the restricting factor in regard to growth and population survival. Other factors, such as the competition with bryophytes, insufficient diaspore dispersal or forest management practice must account for the small population sizes. The described transplantation technique of vegetative diaspores has proved to be very useful for the augmentation of small populations without damaging the existing thalli and we suggest use of this method for in situ conservation of endangered lichen species.
43 citations
TL;DR: CO2 gas exchange measurements carried out in the laboratory confirmed the high metabolic activity of isidia, and the different roles played by isidia in the biology of Pseudevernia furfuracea, and particularly their rejuvenating effect on aged lobes are discussed.
Abstract: The development of isidia in thalli of Pseudevernia furfuracea from the Carnic Alps (North-eastern Italy), and the effects of these structures on CO2 gas exchanges were investigated. The ontogenetic events were studied by comparison of sections stained with different histochemical tests and SEM observations. A high cell turnover rate in both symbiotic partners is the first sign of isidium development, followed by an increased aplanosporogenesis of algae and growth of neighbouring medullary hyphae which become oriented upwards. Large nuclei and an intense cytoplasm activity characterize the mycobiont cells. The surface of very young isidia shows an irregular structure of spherical to ovoid protruding tips of perpendicular cortical hyphae, that are later organised in a pseudomeristematic area similar to that observed in the apex of growing lobes. CO2 gas exchange measurements carried out in the laboratory confirmed the high metabolic activity of isidia. At optimal water content and favourable light conditions, isolated isidia had rates of gross photosynthesis and dark respiration that were twice those of non-isidiate lobes. Isolated isidia also had a very low CO2 saturation point, probably because of their favourable surface/volume ratio, and a high light saturation, probably linked to their high content of photosynthetic pigments. The different roles played by isidia in the biology of Pseudevernia furfuracea, and particularly their rejuvenating effect on aged lobes, are discussed, and the presence of thalloconidia is briefly mentioned.
43 citations
TL;DR: Although presenting layers typical of the heteromerous structure of Parmeliaceae lichens, the studied species have very distinct anatomical details including: the type of upper cortex, medulla thickness, hyphal orientation pattern and distinct strata in this layer, variations of crystal shape, color, location and degree of association with medullary hyphae, rhizines thickness and covering by a cortex.
18 citations
TL;DR: A revision of the North American members of the Leptogium saturninum group is presented based on molecular phylogenetic analyses of mtSSU and nrITS sequence data, together with an extensive morphological study.
Abstract: A revision of the North American members of the Leptogium saturninum group (i.e. species with long lower-surface hairs, isidia, and usually smooth upper surface) is presented based on molecular phylogenetic analyses of mtSSU and nrITS sequence data, together with an extensive morphological study. Three species supported by both molecular and morphological characteristics are recognized: L. acadiense sp. nov. (distinguished by granular saturninum-type isidia, medulla composed of irregularly arranged or perpendicular hyphae), L. cookii sp. nov. (distinguished by cylindrical saturninum-type isidia) and L. hirsutum (distinguished by hirsutum-type isidia and medulla composed of loosely intertwined hyphae). One species supported by morphological characteristics, but for which no molecular data could be generated, is also recognized: L. compactum sp. nov. (distinguished by hirsutum-type isidia and medulla composed of tightly packed hyphae). Finally, L. saturninum (distinguished by granular saturninum-type isidia and medulla composed of perpendicular and parallel hyphae) is supported by morphological characteristics but molecular data from geographically diverse populations, including those near the type locality, indicate that the morphologically defined species is paraphyletic. Leptogium burnetiae is excluded from North American based on morphological study of the type. The species are described and illustrated in detail, and are distinguished morphologically by their isidium development, morphology of mature isidia, and pattern of hyphae in the medulla in transverse sections near lobe margins. A key to the members of the L. saturninum group and related species is also presented.
18 citations
TL;DR: Comparisons of the ITS sequences, both in phylogenetic analysis and secondary structure models of ITS2, support the taxonomic distinctiveness of this species.
Abstract: In an investigation of Peltigera species in montane forests of northern China, a new species, P. isidiophora was identified based on morphological characteristics and DNA sequence data. It differs morphologically from other members of the P. canina-group by its laminal clustered isidia occurring in pits, shiny upper surface, and its slender, scattered and simple rhizines. It also differs chemically from morphologically similar species by two unnamed terpenoid metabolites detected by thin layer chromatography in solvent systems C and G. Comparisons of the ITS sequences, both in phylogenetic analysis and secondary structure models of ITS2, support the taxonomic distinctiveness of this species. A synoptic table to morphologically similar species, and a key to the species in the Peltigera canina group from China are provided.
12 citations
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| Year | Papers |
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| 2016 | 1 |
| 2015 | 1 |
| 2009 | 1 |
| 2005 | 1 |
| 2000 | 1 |
| 1999 | 1 |