Thallus anatomy of Canoparmelia texana (Parmeliaceae, lichenized Ascomycota) / Anatomia do talo de Canoparmelia texana (Parmeliaceae, Ascomycota liquenizados)

Conventional techniques for structural studies under light microscope and scanning electron microscope were employed to describe the histology of thallus in Canoparmelia texana, a lichen with wide distribution in open environments and fairly common in the cerrados and urban areas of Brazil. This study describes a new type of cortical organization for the family Parmeliaceae, in C. texana the upper cortex is lacunar, showing a large quantity of small intercellular spaces or lacunae. The anatomical features including medulla thickness, hyphal orientation pattern, rhizines thickness and crystals inclusions have an important adaptive role for the success of C. texana in Brazilian cerrado, a savanna-like ecosystem.

Técnicas convencionais para estudos anatômicos em microscopia de luz e microscopia eletrônica de varredura foram utilizadas para descrever a histologia do talo de Canoparmelia texana, um líquen com ampla distribuição em ambientes abertos e bastante comum nos cerrados e em áreas urbanas no Brasil. Este estudo descreve um novo tipo de organização cortical para Parmeliaceae. Em C. texana o córtex superior é lacunar mostrando uma grande quantidade de pequenos espaços intracelulares. As características anatômicas incluindo a espessura da medula, o padrão de orientação das hifas, espessura das rizinas e inclusões de cristais aparentemente possuem um importante papel adaptativo para o sucesso de C. texana nos cerrados brasileiros.

Cortical diversity in three species groups of Parmotrema sensu lato (Parmeliaceae, lichenized Ascomycota).

Conventional techniques for structural studies under light microscope were employed to describe and compare the upper cortex anatomy in three species groups of Parmotrema sensu lato. This study indicates that there is a pattern in the structure of the upper cortex in all the three groups of Parmotrema species studied here, and this pattern can be used to place each species group separately within the genus Parmotrema. Although the species of Parmotrema studied have palisade prosoplectenchymatous upper cortex, there are clear differences between the analyzed groups. The upper cortex of Parmotrema s. str. can be characterized by more elongated cells and very compressed hyphae with small interstices between them; the upper cortex of the species with reticular maculae is characterized by the presence of maculae produced by the organization of hyphae that rise towards to the upper cortex and that are not so compressed, while the upper cortex of the species with dimorphic rhizinae has less elongated almost-rounded cells without interstices or cracks but is generally accompanied by aeroplectenchyma. Besides, the first cell layer of the upper cortex presents differential staining by toluidine blue and the epicortex is tightly attached to it.

Thallus structure and isidium development in two Parmeliaceae species (lichenized Ascomycota).

(Thallus structure and isidium development in two Parmeliaceae species (lichenized Ascomycota)). Conventional techniques for structural studies under light microscope and scanning electron microscope were employed to describe and compare the histology of thallus and isidia development in Parmotrema tinctorum and Parmelinopsis minarum. 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 cortical layer. Isidium formation starts with cortical cell proliferation, which results in a small protuberance on the thallus surface, followed by the photobiont cell proliferation. Medullary hyphal intrusions occur only after the formation of this protuberance. In this stage medullary hyphae grow, ramifying or not inside the protuberance. In a posterior stage, the isidium base becomes constricted, which facilitates its detachment from the thallus.

Evaluation of different protocols for anatomical studies in Parmeliaceae (lichenized Ascomycota).

Anatomical information on most lichen species, including Parmeliaceae species, is scarce and superficial. This is partially due to the technical difficulties found during the preparation of samples and sections suitable for optical microscopy analysis. There is a lack of pictures of anatomical sections as well as detailed anatomical protocols related to the sample processing made by specialized plant anatomists in literature. This work aimed to look for a standardized histological technique and to develop a protocol for histological studies of foliose Parmeliaceae under light microscopy. Four common pantropical species of Parmeliaceae, abundant in the Brazilian cerrado vegetation, were processed in several ways in relation to fixing and inclusion media, sectioning thicknesses, and staining, including both fresh and 2-year-old herbarium specimens. The best technique found for anatomical studies of Parmeliaceae under light microscopy is represented by 2 or 3 microm thick sections of fresh or herbarium samples, desiccated and fixed in FAA 50, infiltrated and embedded in glycol-methacrylate resin (Leica), and stained by Toluidine Blue or Methylene Blue.