Gabriela E. Giudice

Morphology and ultrastructure of megaspores and microspores of Isoetes savatieri Franchet (Lycophyta)

Abstract The general morphology, organization, structure and ornamentation of the sporoderm of megaspores and microspores of Isoetes savatieri Franchet have been studied with a stereoscopic microscope, light microscopy, transmission and scanning electron microscopy. The megaspores are trilete, 420–580 μm in equatorial diameter, subtriangular to globose in polar view with an evident equatorial flange (zone). The ornamentation is rugulate. A siliceous cover with a three-dimensional network overlies an exospore sporopolleninous apparently laminar with an equatorial–distal separation of laminae. Each exospore lamina is fused to those of other planes delimiting lacunae. The lacunae located in the outer part of the exospore are filled with silica. The endospore is thick, its structure is fibrillar. In section it is apparently composed of two zones. The microspores are monolete, 35–40 μm long and 20–25 μm wide and elliptic in polar view. A supra-laesural expansion is present. The sculpture is microechinate. A contrasted perispore composed of thin joined threads that form a lacunose structure can be distinguished in the microspore sporoderm. Two parts of the underlying exospore structurally different are evident: a laminar outer part and an inner part, mostly compact. An equatorial–distal separation between both parts of the exospore is evident. The endospore is fibrillar. The ultrastructural similarity of the spores of I. savatieri with those previously studied in Isoetes can be regarded as indicative of the homogeneity of this group of living lycopsids.

Spore Morphology of the Polypodiaceae from Northwestern Argentina

Abstract The spores of the following genera of Polypodiaceae growing in northwest Argentina were analyzed: Campyloneurum, Microgramma, Pecluma, Phlebodium, Pleopeltis and Polypodium. The study involved analyses of herbarium material using light microscopy and scanning electron microscopy. The spores are monolete, 40–90 μm in major equatorial diameter, eliptic to oblong in polar view and plane to concave-convex in equatorial view. The exospore ranges from 2–5 μm thick, is apparently double-layered, with a verrucate or tuberculate surface that is usually perforated. The perispore ranges from 0.3–1 μm thick, is apparently single-layered, attached to the exospore, perforated, and generally smooth or in some cases micro-ornamented. Most of the taxa analyzed have globules on the surface. These are single or associated in masses and irregularly distributed. Characteristics such as size, shape and exospore and perispore sculpture allow us to differentiate among some of the genera as well as recognize species groups. Microgramma, Campyloneurum, Pecluma, Pleopeltis and Polypodium have verrucate spores whereas those of Phlebodium are tuberculate.

Microspore Morphology of Isoetes Species (Lycophyta) from Southern South America

Microspores of the 24 species ofIsoetes that grow in southern South America were analyzed under a light microscope and scanning electron microscope. The microspores are monolete, elliptic in polar view, 30–40 μm long, and 20–25 μm wide. A background with various characteristics is seen on each surface. A supra-laesural expansion is present. The perispore is ornamented and has a perforated background. In section, it has a lacunose structure. The exospore is smooth, and it has a compact structure in section. The studied species could be divided into three groups by their perispore ornamentation: equinate, rugulate, and tuberculate. Microspore size was positively correlated with increasing ploidy level, and larger microspores were associated with terrestrial habitats. A convergence in ornamentation was found between spores produced by the studied species and those that grow in regions outside of the area under study.ResumenSe analizaron con microscopio óptico y electrónico de barrido las microsporas de veinticuatro especies deIsoetes que crecen en Sud América Austral. Las microsporas son monoletes, elípticas en vista polar, de 30–40 μm de longitud y 20–25 μm de ancho. En superficie se observa una base con diversas características. Una expansión sobre la lesura está presente. El perisporio está ornamentado y tiene una base perforada. En sección, tiene una estructura lacunosa. El exosporio es liso y en sección tiene estructura compacta. Las especies estudiadas se pueden reunir en tres grupos de acuerdo a la ornamentación del perisporio, estos son: equinado, rugulado y tuberculado. Se ha observado que existe una correlación positiva entre el tamaño de las microsporas y el incremento en el nivel de ploidía y el hábitat. Se observó una convergencia en la ornamentación entre las esporas producidas por las especies estudiadas y las producidas por otras especies que crecen en regiones fuera del área de estudio. Palabras clave: Sud América,Isoetes, microsporas, morfología, escultura

Comparative palynological analysis of Lygodium venustum Sw. and L. volubile Sw. (Lygodiaceae)

The genus Lygodium Sw. is one of the few climbing ferns in the world. The spores of L. venustum Sw. and L. volubile Sw. were studied using light, scanning, and transmission electron microscopy. This work is based on herbarium material. The spores are trilete, triangular, with straight to convex sides in polar view. The equatorial diameter is 72-104 µm, and the polar diameter is 64-84 µm. The ornamentation in L. venustum is verrucate-tuberculate while in L. volubile, it is verrucate-tuberculate in the proximal face but with a few ridges on the distal face, where a micro-ornamentation constituted by verrrucae and tubercles is observed. An equatorial ridge is also present. The exospore is two-layered; in L. venustum, it is smooth in contrast with the ornamented exospore of L. volubile. The perispore of the two species analyzed is similar. This wall is four-layered with particular elements arranged radially in the middle layer. On the spores surface of both species, few spheroids are observed. The results introduced in the current study may be useful for the systematics of the genus as well as for phylogenetic purposes.

Morphology and ultrastructure of heterosporous Filicophyta spores from north‐west Argentina

Mega‐ and microspores of heterosporous Filicophyta (Azolla cristata Willd., A. filiculoides Lam., Marsilea ancylopoda A. Braun, M. mollis Rob & Fern. and Salvinia minima Baker) that grow in north‐west Argentina were studied by stereo microscopy, light microscopy, scanning electron microscopy and transmission electron microscopy. The spores of Salvinia minima were analyzed for the first time. The mega‐ and microspores morphology and sporoderm structure as well as the type of microspore aggregation enable determination of the taxa at generic level, and at specific level in Azolla. Both species of Azolla can be differentiated by their megaspore surface and wall ultrastructure. The microspore ornamentation in Marsilea is variable even within the same sporocarp. These differences could be related to different stages in spore maturation.

Spore morphology and sporoderm ultrastructure in Adiantopsis Fée (Pteridaceae‐Pteridophyta) from Argentina

The aim of this study is to analyse, describe and compare the spores of the two Adiantopsis species that grow in Argentina, A. chlorophylla (Sw.) Fée and A. radiata (L.) Fée. The study used herbarium material observed with light microscopy (LM), scanning electron microscopes (SEM) and transmission electron microscopes (TEM). The spores of both species are trilete with an echinate surface. The exospore is smooth, two‐layered in section; both layers with different thickness and contrast. Depending on the plane of sectioning, channels are seen running through the exospore and in the apertural region. The perispore strongly contrasted when seen with TEM, is two‐layered and bears ornamentation. The two layers have different thickness and structure. The inner layer P1 is the thickest layer and has three strata, which form the sculptural elements. The outer layer P2 covers all the surfaces of P1. Two levels of ornamentation are clearly distinguished: a basal level composed of fused ridges, and an upper level composed of echinae. The spores of A. chlorophylla are triangular‐globose in polar view, with convex sides, 25 – 50 µm in equatorial diameter and have more ornamental processes per surface unit than the spores of A. radiata. The spores of A. radiata are triangular in polar view and 30 – 40 µm in equatorial diameter. Size and ornamentation help to establish differences at species level, and together with the exomorphological characteristics of the sporophyte, contribute to the systematics of this genus.

Microspore Morphology of Isoetes Species (Lycophyta) from Southern South America. Part II. TEM Analysis of Some Selected Types

The microspores ofIsoetes escondidensis, I. gardneriana, I. herzogii, I. pedersenii, andI. savatieri were analyzed with transmission and scanning electron microscopy. The selected species were found to be representative of the diversity found in 24 taxa previously studied that grow in southern South America. The sporoderm is similar in the five types and is composed, from the outside to the inside, of perispore, para-exospore, exospore, and endospore. InI. escondidensis, I. gardneriana, I. herzogii, andI. savatieri, the perispore is lacunose, whereas inI. pedersenii, it is camerate. The para-exospore is formed of large superimposed and fused bars, which are more numerous and thicker in immature spores. The exospore shows uniform characteristics and a strongly contrasted cover. It has pluristratified zones on both sides of the aperture. The presence of radial rodlets between the para-exospore and exospore and in the supra-apertural chamber is described here for the first time. The endospore has a fibrillate or reticulate structure, or both structures may be present. A boundary within the fibrillate endospore is evident, which might be related to stages of deposition. The surface characteristics are formed by either the middle and outer strata of the perispore or elements on the outer surface, as inI. escondidensis. The characteristics of the microspore surface and of the perispore structure provide characteristics useful for systematic purposes at the infrageneric levelResumenLas microsporas deIsoetes escondidensis, I. gardneriana, I. herzogii, I. pedersenii yI. savatieri fueron analizadas con microscopios electrónicos de transmisión y barrido. Las especies seleccionadas son representativas de la diversidad encontrada en los 24 taxa que crecen en el Cono Sur de América Meridional previamente estudiados. La compositión de la esporodermis es similar en los cinco tipos, diferenciándose desde afuera hacia adentro, perisporio, para-exosporio, exosporio y endosporio. EnI. escondidensis, I. gardneriana, I. herzogii yI. savatieri el perisporio es lacunoso, mientras que enI. pedersenii es camerado. El para-exosporio está constituido por barras largas, superpuestas y fusionadas cuyo número y espesor es mayor en esporas inmaduras. El exosporio presenta características uniformes y posee una cubierta fuertemente contrastada con zonas pluriestratificadas a ambos lados de la abertura. Se cita aquí por primera vez la presencia de varillitas entre el para-exosporio y el exosporio y en la cámara supra-abertural. El endosporio es fibrilar o reticulado. En el fibrilar se distinguen dos capas que tendrían relatión con las etapas de depositación. Las características superficiales están definidas por el perisporio, específicamente por los estratos medio, externo o por elementos por encima de este, como enI. escondidensis. Las características de la superficie de las microsporas y la estructura del perisporio, podrían ser útiles para fines sistemáticos a nivel infra-genérico

Spore wall ultrastructure of Polypodiaceae from north-western Argentina

Abstract The spore wall ultrastructure of Campyloneurum, Microgramma, Pecluma, Phlebodium, Pleopeltis and Serpocaulum (Polypodiaceae) from north-western Argentina has been studied using transmission electron microscopy (TEM). The exospore is 0.4–3 μm thick, two-layered and variously ornamented in all taxa. The exospore surface is distinctive, but in general ultrastructure the exospore is similar in all species studied. The structural elements of the exospore consist of cavities in the inner part as well as channels with a radial orientation and channels at both sides of the laesura. Variation in the exospore surface was observed in spores at different stages of maturation. The perispore is darkly contrasted and 0.04–2 μm thick. Three different structure types were recognised, including fibrillar, multilamellar and lacunose. Scattered globules and spherules were always present on the perispore surface. The structural variability of the perispore was surveyed within complete sporangia. We concluded that the observed variability may be related to the stage in spore maturation and, consequently, to the stages in perispore differentiation. As the exospore ultrastructure is similar and interpreted as related to functional activity in the studied material, it cannot be used for systematic delimitations at this generic or specific level.

Palynological analysis of Sphaeropteris gardneri (Cyatheaceae, Pteridophyta)

The spore morphology and wall ultrastructure of Sphaeropteris gardneri (Hook.) R.M. Tryon from Brazil were analyzed with LM, SEM and TEM. The spores are trilete with an ornamentation formed of short low ridges with spines in their margins. The exospore is 2.5microm thick, two- layered in section and single or branched channels are present. The perispore is 1.2microm thick and two-layered. The inner layer has three strata: the inner stratum is formed of a network of branched and fused threads, the middle stratum has threads with a radial orientation and in the outer stratum thin, dark fibres are immersed in a less dense contrasted matrix. The outer layer of the perispore is the one that forms the echinate-ridges and is constituted of threads arranged in a compact way. Globules of different sizes are observed on the surface. The differences found in the perispore ornamentation and ultrastructure in Alsophila, which was previously studied, and those of Sphaeropteris, show a tendency to wall complexity.

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.