Observations of the development of Xanthoparmelia farinosa under optical and electron microscopy

Renato Andrés García,Vilma Gabriela Rosato

doi:10.1080/21501203.2017.1367333

Renato Andrés García, Vilma Gabriela Rosato

Open Access

https://doi.org/10.1080/21501203.2017.1367333

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Abstract

ABSTRACTXanthoparmelia farinosa is a foliose lichen widely distributed in South America, growing not only on rocks but also on man-made structures. This species has abundant soralia, but it is unknown how development occurs from the soredium to the formation of a complete thallus. The soredia were extracted from the thallus with forceps, planted on glass plates and exposed to outdoor conditions for a period of 24 months; in every 3 months, optical inspection was performed with a stereomicroscope and a compound microscope, in addition, four samples with different exposure times were chosen to observe under a scanning electron microscope. The development of hyphae and the adhesion of these to the substrate, and the outlines of the formation of the lobules and rhizines could be observed. Our study is a first attempt to understand the development of this species which is endemic to South America and very common in the area.

Highlights

Foliose lichens have a flat continuous thallus and radial growth, with a distinctive upper cortex, and a lower cortex attached to the substrate, usually by rhizines
Using a stereoscopic microscope and forceps, soredia were extracted from soralia and seeded on glass slides 7.5 × 2.5 cm
There was no evidence that the loss has been caused by animal feeding, so we interpreted that the loss of this mass of soredia is caused by the lack of an efficient attachment structure

Summary

Introduction

Foliose lichens have a flat continuous thallus and radial growth, with a distinctive upper cortex, and a lower cortex attached to the substrate, usually by rhizines. Many foliose thallus margins consist of individual marginal lobes exhibiting radial growth and periodically divided; this division can give lobules of equal or different size and the result is a complex structure (Aplin and Hill 1979; Hooker 1980; Hill 1984; Armstrong 1991a, 1993). The soredia consist of a few algal cells enveloped by a loose mantle of hyphae; these are small and with a range of 50 mm in diameter. They can be in areas delimited on the upper surface named soralia or scattered without grouping. The size and shape of the resulting thallus depends on the number of soredia involved in its formation, and this is frequently scattered in groups of various sizes (Armstrong 1990)

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