María Luján Luna

PATTERNS OF DECAY CAUSED BY PYCNOPORUS SANGUINEUS AND GANODERMA LUCIDUM (APHYLLOPHORALES) IN POPLAR WOOD

Populus deltoides clones are widely planted in Argentina, in a region called “Parana River Delta”. In this site, Pycnoporus sanguineus and Ganoderma lucidum (Aphyllophorales) cause white-rot decay in both living and felled poplar trees. The purpose of this work was to estimate, through laboratory decay tests, the ability of both fungi to degrade poplar wood and to describe the patterns of decay using light and scanning electron microscopy. Two exposure times were analyzed: 75 and 150 days. The percent weight loss produced by both fungal strains was similar for both exposure periods (c. 50–60% of wood mass) but microscopic observations showed there were different patterns of decay. Samples inoculated with P. sanguineus showed a selective delignification, whereas those inoculated with G. lucidum exhibited a combination of simultaneous decay and selective delignification. Separation among cells was the main diagnostic feature for selective decay. By contrast, the presence of erosion troughs, cell wall thinning, bore holes, rounded pit erosion and erosion channels were diagnostic for the simultaneous type of decay.

Characterization of Schinopsis Haenkeana wood Decayed by Phellinus Chaquensis (Basidiomycota, Hymenochaetales)

Schinopsis haenkeana is a native tree to the Chaco Serrano Forests in Argentina. The white-rot fungus Phellinus chaquensis degrades its wood, causing a whiterot type of decay. The objective of this study was to investigate the structural alterations caused by P. chaquensis in S. hankeana decayed naturally and in vitro. Sound living branches with decay and basidiocarps of P. chaquensis were sampled from the field and in vitro decay tests were performed according to the ASTM D-2017-81 standard method. Naturally decayed branches exhibited an innermost discolored zone with white-rot decay and an outer yellowish-white portion of sound sapwood. Using LM and SEM, degraded tissue displayed diagnostic characters of selective delignification and simultaneous decay. Findings indicate that P. chaquensis causes a mottled pattern of decay (selective delignification plus simultaneous decay) in S. haenkeana wood. Other features such as accumulation of extractives, profuse deposition of crystals and tyloses, typical ofSchinopsis spp. heartwood, were additionally observed. In laboratory degraded material, signs of selective delignification and incipient stages of simultaneous decay were noticeable only microscopically. Chemical analysis revealed an oxidative alteration of aromatic moieties in naturally decayed samples which might be related to the accumulation of phenols as a response to fungal attack when compared to sound samples. Naturally degraded sapwood exhibits anatomical and chemical modifications that indicate the development of discolored wood derived from the host-pathogen interaction.

Blechnum ludificans Herter, an Overlooked Fern from South America

ABSTRACT In this paper the authors reconsider the validity of the fern Blechnum ludificans Herter. Herbarium material was studied using stereoscopic microscopy, LM and SEM. The main diagnostic characters of B. ludificans are: pinnate to pinnate- pinnatisect pinnae, 25 or fewer pinnae per blade, the presence of glandular hairs on the pinnae, inframedial position of the coenosori, and entire rhizome scale margins. Illustrations of the diagnostic features of B. ludificans are provided.

Revision of the Genus Salpichlaena J. Sm. (Blechnaceae, Pteridophyta)

ABSTRACT Salpichlaena J. Sm. (Blechnaceae) is a genus of climbing fern that grows in Central and South America. The number of species recognized for this genus varies according to different authors from one to four. The goal of this work was to provide a systematic revision of the genus Salpichlaena in order to contribute to the knowledge of the fern biodiversity in America. For this purpose morphological, anatomical and palynological characters were analyzed in material from the geographical distribution of Salpichlaena. Herbarium specimens were treated according to the standard techniques for LM and SEM studies. The type specimens and the original descriptions were consulted to determine the applications of names. Two species are recognized, S. volubilis (Kaulf.) J. Sm. and S. hookeriana (Kuntze) Alston. Salpichlaena hookeriana differs from S. volubilis by pronounced foliar dimorphism (the fertile pinnules are much reduced), the presence of foliar buds on sterile basal pinnules, ovate costular scales and the presence of glandular hairs on the abaxial surface of the costa. The spores are monolete in both taxa, with rugulate-granulate perispore and superficial spherules. Salpichlaena volubilis is widely distributed in Central and South America, from Guatemala and Caribbean Islands, up to southern Brazil and Bolivia, across a wide altitudinal range of 200 to 1900 m. Salpichlaena hookeriana grows from Colombia, Venezuelan Guyana, Suriname, British Guiana, North Brazil to Peru and Bolivia, at altitudes up to 800 m. The diagnostic characters, illustrations and distribution maps of both species are given.

Observations on Tracheary Elements in Salpichlaena J. Sm. (Blechnaceae, Pteridophyta)

ABSTRACT The morphology of the tracheary elements of the climbing fern Salpichlaena (Blechnaceae) were analyzed by means of LM and SEM. Two preparative techniques were employed: maceration and sectioning. Under SEM macerated tracheary elements from roots, rhizomes and leaf rachises showed large scalariform perforations lacking pit membranes, thus constituting apparent perforation plates. The perforations showed terminal as well as lateral positions. “Multiple end-wall” and “intermittent” perforation plates were also observed. In sectioned material tracheary cells exhibited mostly intact pit membranes conforming tracheids with scalariform and circular to oval wall pitting. In roots, true perforations seemed to be present in some tracheary cells. A different degree of pit membrane perforations were registered in both macerated and sectioned material, thus suggesting the existence of “incipient vessel elements”. According to our observations macerations produce alterations in the xylem tissue, which can lead to misinterpretations.

Comportamiento de la madera de "Populus nigra cv Italica" ante la preservación con creosota y CCA

El alamo criollo (Populus nigra cv Italica) es uno de los clones mas cultivados en la Patagonia argentina con el fin principal de proteger cultivos frutihorticolas, pasturas, ganado y construcciones rurales. Historicamente se ha utilizado su madera en la region como poste corto y lena. Sin embargo, nunca ha existido un aprovechamiento intensivo de ella debido a su baja durabilidad natural. La aplicacion de sustancias y tratamientos preservadores permitiria incrementar la vida util de su madera en servicio. Se evaluaron los niveles de absorcion de solucion de creosota en distintas concentraciones y la retencion de CCA, aplicados mediante los tratamientos de celula llena, celula vacia y bano en caliente y frio. Se utilizaron probetas de alamo criollo de reducidas dimensiones, procedente de dos zonas de cultivo en la provincia de Santa Cruz: Los Antiguos y Gobernador Gregores. La madera de Los Antiguos, procedente de mejores condiciones de cultivo, presento la madera menos densa y la mayor tasa anual de crecimiento. Tambien obtuvo los mayores niveles de retencion de CCA y de absorcion de creosota. No obstante tratarse del mismo clon, la procedencia del cultivo determino comportamientos diferenciales ante los tratamientos preservadores, con diferencias en los resultados mas evidentes durante la utilizacion de creosota que con el CCA. Se detectaron diferencias anatomicas importantes entre ambas procedencias pudiendose explicar a traves de estas el comportamiento de las maderas ante los tratamientos preservadores, en especial a partir de la porosidad y del diametro medio de vasos.

Anatomical Features of the Tubercle and Young Sporophyte of the Annual Fern Anogramma chaerophylla Growing in the Punta Lara Natural Reserve (Buenos Aires, Argentina)

Abstract The fern genus Anogramma is characterized by the presence of annual sporophytes and tubercles that persist through dry periods. Tubercles may host embryos that develop when climatic conditions are more favorable. As information on the structure of the tubercle and sporophyte of Anogramma chaerophylla is incomplete, the objective of this work was to analyze anatomical characteristics during development and deepen knowledge of the adaptive strategies of this species. Spores were grown in-vitro and different stages of tubercle development and embryonic sporophytes were fixed in FAA, embedded in Paraplast and analyzed using light microscopy. Initially, the green gametophyte developed antheridia and archegonia in its thickened portion, where later bisexual tubercles differentiated. Embryos developed only from the archegonia located in the tubercles, with one embryo developing per tubercule. During sporophyte growth the reserves accumulated in the tubercle were consumed. Oversized cells were observed at the junction between the green gametophyte and the tubercle, suggesting a possible role in translocation of substances. The young sporophyte consisted of a short shoot and a prominent foot. The placenta comprised the foot cells and the adjacent tubercle cells. The first leaves protruded soon and developed early as photosynthetic organs. Sporophytes remained attached to the tubercles until advanced stages of development. Vegetative propagation was documented in smaller tubercles that did not develop gametangia. Because few sporophytes were observed in vivo, it is likely that natural populations are maintained through vegetative propagation of the gametophyte until favorable conditions encourage development of sporophytes.

Structure and chemistry of the xylem of arborescent species of blechnum from South America

The xylem in three arborescent species of Blechnum section Lomariocycas was studied in detail using SEM, TEM, FT-IR spectroscopy and sugar composition analysis. The overall structure of root and rhizome metaxylem tracheids was similar in the three species analyzed, and characterized by mostly scalariform pitting of these multifaceted cells. Pit membrane thickness and porosity varied according to the stage of tracheid maturation. Approximately rounded deposits resembling vestures were observed in the outer pit apertures of some tracheids. Under TEM, thickenings like one-sided tori appeared on the tracheid side of tracheid-to-parenchyma contact walls; some parenchyma cells showed, in addition, features of transfer cells. As the increase in stature creates new constraints in terms of biomechanical support and water transport in plants, the characteristics found in Blechnum xylem might be related to optimization of conductive efficiency and safety. Chemical analyses of roots and rhizomes of B. yungense revealed similar levels of G-type lignin deposited in the xylem cell walls. Such lignin is the most common in ferns, including other arborescent genera. Preliminary analysis of cell wall polysaccharide composition of both root and rhizome xylem, yielded cellulose, xyloglucans and xylans with low amounts of mannans and pectins. The xylem of rhizomes had higher amounts of cellulose than root xylem. Our results are discussed in the context of functional and evolutionary aspects of xylem ferns.

STRUCTURE AND ULTRASTRUCTURE OF THE TRACHEARY ELEMENTS OF ASPLENIUM (PTERIDOPHYTA) FROM THE "YUNGAS", ARGENTINA

The structure of root and rhizome tracheary cells of Asplenium spp. (Filicales, Pteridophyta) growing in NW Argentina was studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In all cases, tracheary cells consisted of tracheids with various facets, mainly with scalariform pitting. With SEM, intertracheary pit membranes appeared smooth and non porose in most cases. In some instances, porose or web-like to thread-like pit membranes were noticed in rhizome tracheids. Under TEM secondary walls displayed a smooth and uniform appearance. Pit membranes showed a variation in thickness in presumed association with their maturation stage. More mature tracheary cells showed pit membranes with a mesh-like aspect and visible openings or pores. These characteristics are attributed to pit membrane hydrolysis, which facilitates water transport among tracheary cells.