Artificial Cultures of Lichens in the Natural Environment

Abstract

The growth and development of several lichens under natural conditions are studied with the SEM. The results permit observations on the influence of the microclimate and of pollution on thalline development and on some principles of lichen systematics.

Observations of the development ofXanthoparmelia farinosaunder optical and electron microscopy

“…Contrary to that observed by Schuster et al (1985) for P. tenella , rhizines formation in X. farinosa occurs after the formation of lobes and lower cortex. As the studies have been carried out on different species and in different types of climate, it is expected that the same ones do not have a similar speed of development.…”

“…It was also noted that in some cases, these trapped algae joined masses of soredia and exuded an adhesive substance. Whereas the existence of soredia groups joined by hyphae and hyphae trapping algae species has been reported (Schuster et al 1985; Honegger 2008), no mention has been made of a morphological difference between the exclusive anchoring hyphae and binding hyphae as we have seen here. So, we consider this morphological type as exploration hyphae.…”

“…As it was observed by Schuster et al (1985), Scheidegger (1995) and Anstett et al (2014), the first visible structure is the hyaline hyphae with anchor function; Schuster et al (1985) termed this stage “arachnoidal stage” characterised by radiating hyphae. In our case study, we consider that this arachnoid stage appears around 6 months, which Anstett et al (2014) termed aposymbiotic hyphal extension.…”

“…As regards their development, the lobes of X. farinosa grow slower compared to other species of foliose lichens as P. tenella, H. physodes, P. sulcata, L. pulmonaria, P. didactyla and P. praetextata (Schuster et al 1985; Stocker-Wörgötter 1991; Scheidegger 1995; Anstett et al 2014), although the development was faster than that observed for L. scrobiculata (Hilmo and Ott 2002). Contrary to that observed by Schuster et al (1985) for P. tenella , rhizines formation in X. farinosa occurs after the formation of lobes and lower cortex.…”

“…Schuster et al (1985) cultivated soredia under outdoor conditions on bark; in all cases, they observed that an extended network of hyphae secured soredia to the substrate as well as joined other soredia to form a gelatinous tissue. They observed the formation of lobes on Parmelia sulcata, Usnea filipendula and Hypogymnia physodes after 12 months, whereas in Physcia tenella , they were seen at 9 months and rhizines were developed before the formation of lobes.…”