Blanca Pérez-García

Analysis of fern spore banks from the soil of three vegetation types in the central region of Mexico.

The vertical structure of fern spore banks was studied in a xerophilous shrubland, montane rain forest, and pine-oak forest in Hidalgo, Mexico, using the emergence method. Soil samples were collected in April 1999 at depths of 0-10, 10-20, and 20-30 cm. Viable spores decreased significantly with depth in all vegetation types, and the highest number of prothallia and sporophytes was found in the uppermost layer. The montane rain forest and the xerophilous shrubland had the largest and the richest banks, respectively. Twenty-three fern taxa were registered in the aboveground vegetation, 12 in the soil banks, and 43.5% were in both. Aboveground and in the soil bank, the xerophilous shrubland, the montane rain forest, and the pine-oak forest had, 17 and 7, 1 and 6, and 7 and 3 taxa, respectively. These were distributed differentially in relation to depth. The Sørensen index indicated a similarity of 61.5% between the xerophilous shrubland and the montane rain forest, and the Czeckanovsky index indicated 19.75%. The presence of viable spores in the soil of all vegetation types confirmed the existence of natural spore banks. Long-distance dispersal was an important factor determining the specific composition of the xerophilous shrubland and the pine-oak forest.

Effect of fire on the germination of spores of Pteridium caudatum, an invasive fern.

Pteridium caudatum is a fern that frequently invades burnt areas in the Yucatan Peninsula and other neotropical sites. While post-tire regeneration of this fern apparently occurs mainly by vegetative means, little is known about the role of its spores in post-fire regeneration and in colonization of newly invaded fields. Central to these questions is whether bracken fern spores maintain their viability after fires. Here we experimentally evaluate the effect of fire-induced temperatures on Pteridium caudatum spore germination. We used 1200-cm 3 blocks containing a constant fuel load of 47.4 g of litter, in which we placed spores at three different depths. The blocks were then ignited, and temperatures at each depth were monitored at 1-min intervals for 2 h. One day after the experimental fires, spores were dug out and cultured at 25 °C and 12-h light/dark cycles. Soil temperatures decreased significantly in relation to depth during fires. Spores on the surface were severely affected by fire, while those buried at 1 and 3 cm showed 77% germination. Germination in unburned controls was 86%. Our results suggest that during fires, Pteridium caudatum spores buried a few centimetres below the surface have a high percentage of viability, which could explain the rapid establishment of this species in burnt fields.

Developmental gametophyte morphology of seven species of Thelypteris subg. Cyclosorus (Thelypteridaceae)

The morphogenesis of the sexual phase of seven species of Thelypteris subg. Cyclosorus (Thelypteridaceae) is described and compared. Spores of all species are monolete, ellipsoid and have positive photoblastism. They have Vittaria-type germination, germinal filaments are short and uniseriate, and Aspidium-type development. Adult gametophytes are spatulate-cordiform, and have wide wings with numerous glandular, marginal and superficial hairs. Antheridia have a narrow or widened basal cell, an undivided annular cell, and an opercular cell; antherozoids are liberated through three mechanisms. Archegonia have short necks and four triangular cells on the necks mouth. The sporophytes first leaf is lobed, with open dichotomous veins, glandular hairs similar to those of the gametophyte, and anomocytic stomata. Differences observed between the studied species are: spore size; ornamentation of the perispore; germination and emergence periods; size of hairs; developmental period of gametangia; and antherozoid liberation mechanisms through total detachment of the operculum, partial detachment of the operculum, and development of an apical pore through tearing of the operculum. These taxonomically valuable characters, combined with the sporophyte characteristics, can be useful tools in the identification of the species studied to the subg. Cyclosorus.

A Contribution to the Gametophyte Morphology and Development in Several Species of Thelypteris, Thelypteridaceae

Abstract A contribution to the study of the gametophytes morphology and development of some species of Thelypteris Schmidel (Thelypteridaceae). The development and morphology of the sexual phase of five species of the Thelypteridaceae family is described and compared. Spores were sown in Thompson medium with agar, germination occurred after 11 days; all spores of the species studied are monolete, ellipsoid with a pleated perine, brown to dark brown; the germination pattern is Vittaria type and the prothallial development is Aspidium type. Gametangia are of the common type of the leptosporangiate ferns. Sporophytes in Thelypteris reptans var. reptans and T. tetragona appear 90–285 days after sowing; T. dissimulans, T. piedrensis and T. oviedoae did not develop any sporophytes. The sexual phase of these species has many morphological characteristics in common with species of the Old and New Worlds.

Development of the Sexual Phase of Pseudocolysis bradeorum (Polypodiaceae)

Abstract The development and morphology of the sexual phase of Pseudocolysis bradeorum (Polypodiaceae) are described from material collected in Finca La Selva, near Puerto Viejo, Province of Heredia, Costa Rica. Spores were sown in Thompson medium with agar (25 Petri dishes) and germinated after seven days; the germination pattern was Gleichenia-type and the prothallial development Drynaria-type. Gametangia were typical of homosporous leptosporangiate ferns. Sporophytes appeared after seven months of culture. The sexual phase of this species shares many morphological characteristics with Old and New World species of Polypodiaceae. There is a tendency for vegetative propagation with Pseudocolysis gametophytes.

Observations of the spore, gametophyte and young sporophyte of Pteridium caudatum (L.) Maxon using scanning electron microscopy.

This paper describes the development of the sexual phase of the invasive fern, Pteridium caudatum, from spore germination to young sporophyte formation. Spores samples for gametophyte cultures were taken from various sporophytes and then sown on mineral agar with Thompsons media. Gametophytes were maintained under fluorescent light on a 12h light, 12h dark cycle at 24-25°C. Developmental phases were fixed in FAA-sucrose solution and processed for observation with the scanning electron microscope. Spores are trilete and germination takes place on the second day after sowing; germination is of the Vittaria-type. Adiantum-type prothallial development was observed. The differentiation of a two-dimensional thallus begins 5 days after germination maturation of adult gametophytes occurs about 30 days after sowing. Adult gametophytes are heart-shaped, bisexual and glabrous. Antheridia are formed by three cells: basal, annular and opercular cell with a pore. Archegonia have a neck of 4-cells. The young sporophyte becomes visible within 8 weeks after spores are sown. The taxonomic significance of the gametophyte morphology is discussed.

Gametophyte morphology of Platycerium andinum Baker and Platycerium wandae Racif.

This paper describes the morphology of the sexual phase and spores of Platycerium andinum and Platycerium wandae. Spores were sown in Thompsons media and the cultures were kept at 24-25 degrees C, with 12h light/darkness photoperiod. Developmental phases were fixed in FAA and processed for observation with the scanning electron microscope. Spores of both species are monolete; Vittaria-type germination and Aspidium-type prothallial development were observed. In the phase of development, the gametophytes develop unicellular secretory and as they mature, develop bifurcated or branched pluricellular trichomes, both in the cushion and near the meristematic zone. Adult gametophytes in culture are cordiform-spatulate to cordiform-reniform, most are unisexual and a few are bisexual. Gametangia belong to the leptosporangiate fern type. Archegonial morphology is uniform, with an elongate, thin neck curved toward the base of the gametophyte. Antheridia have a basal cell, an annular cell and an undivided opercular cell. Three hundred days after the spores were sown, sporophytes still had not developed. In both species, some spores germinate inside the sporangial capsule (intra-sporangial germination). We provide new information on morphogenesis in the genus Platycerium.

Spore Germination of Three Tree Fern Species in Response to Light, Water Potential, and Canopy Openness

Abstract The response to the canopy openness of species in tropical forests is a source of niche differentiation. The tree ferns Alsophila firma, Cyathea divergens and Lophosoria quadripinnata coexist in a cloud forest in Mexico; the first is abundant in creeks, the second occupies slightly open places, and the third prefers more open sites. We hypothesized that the distribution of these species would be correlated with their germination patterns. To test the hypothesis we evaluated the effect of light, water potential and canopy openness on spore germination. Spores were incubated under different light filters modifying red∶far-red ratio or light intensity, water potential was modified with polyethylene glycol solutions and distinct canopy openness were selected in the field. No germination occurred in darkness, and it was low under red light and far-red light; however, all species germinated at a very low photon flux density (PFD, 0.04 µmol m−2 s−1). The decrease of water potential from 0 MPa to −0.7 MPa reduced germination in all species, from 98.6% to 72.2% in L. quadripinnata, 66.4% to 18.9% in A. firma and 74.2% to 4.1% in C. divergens. The increase of the canopy openness reduced the germination capacity of the three species, but L. quadripinnata was the least affected. The germination requirements of the three tree fern species were partially related to the distribution of the sporophytes in the cloud forest.

A Pluviometric Fern Spore, Fungal Spore, and Pollen Trap

Abstract Although rain is the most important agent in airborne biological particle deposition most of the current sampling traps retain palynomorphs (fern spore, fungal spore, pollen, among others) but are unable to measure precipitation. The objectives of this study are to present a new simple pluviometric/gravimetric spore/pollen trap and propose a spore/pollen-density rain method, based on the particle frequency and sampling area, which would facilitate ecological inferences about rainfall and Biological Airborne Particle (BAP) deposition, so as to avoid the overrepresentation of the percentage and diverse aerobiological methods. Relative to other spore traps, our proposed trap is simple to build, easy to mount in the field, easy to carry, maintenance free, and requires no energy source. In addition, our trap records rainfall volume, and the quantity of spores captured can be expressed in terms of area-density (particle m−2). The rainfall measured with the trap had no significant differences with the precipitation volume obtained from the pluviometer of the Automatic Meteorological Station at Zacualtipán, Hidalgo, Mexico.

Gametophyte Morphology in Three Mexican Species of Bolbitis (Lomariopsidaceae)

ABSTRACT The development of gametophytes in Bolbitis bernoullii, B. portoricensis and B. umbrosa (Lomariopsidaceae) is described and compared. Spores are monolete, ellipsoid with prominent winged perispore. Germination is of the Vittaria type and the prothallial development is of the Drynaria type. Collenchyma-like thickenings at the corners of the wing cells were not observed. Adult gametophytes are cordate with scarce marginal hairs near the shallow notch. Gametangia are of the common type found in homosporous leptosporangiate ferns. Bolbitis portoricensis develops the first leaf of the sporophyte after 6 to 8 months, with polocytic stomata. In B. portoricensis, vegetative propagation is present in old thalli 6 to 8 months after cultivation.