Experimental Studies of Apospory in Ferns

Apospory in Pteridium aquilinum was found to have several novelfeatures, in particular the rapidity of its occurrence. Outgrowthsfrom detached laminae were detected in as little as 3 days.There was no evidence that failure of co-ordination betweencells, senescence of the sporophytic tissue or unfavourableculture conditions effected the initiation of outgrowths asearlier workers have suggested. The response of Thelypterispalustris was notably slower and more in line with earlier reportsof apospory. Marsilea vestita appeared to be incapable of anyform of aposporous behaviour. The only feature common to all occurrences of apospory in leavesof wild-type ferns is the severance of the lamina from the mainbody of the plant. It is proposed that this may deprive thecells of regulatory substances which maintain the activationof sporophytic genes. The results are also considered in relationto the phase changes in homosporous and heterosporous plantsand the behaviour of fern protoplasts in culture. apospory, ferns, Pteridium aquilinum, Marsilea vestita, Thelypteris palustris     

Effects of Sodium Selenite on the Growth of Bracken Fern Root Callus

Sodium selenite promotes the growth of bracken fern root callusgrowth over a narrow, low range of concentrations, while higherconcentrations are strongly inhibitory. Pteridium aquilinum, bracken fern, sodium selenite, selenium, callus     

The Effect of Colchicine on Spermatogenesis in a Fern, Pteridium aquilinum (L.) Kuhn

Treatment of developing antheridia of Pteridium aquilinum for24 h with radioactive and normal colchicine resulted in spermatocyteswith restitution nuclei, binucleate spermatocytes with multipleimmature blepharoplasts, and spermatids in which the organizationof the microtubular ribbon and basal bodies, and the shapingof the nucleus were seriously disturbed. The results indicatethat the coiling of the multilayered structure and the condensationof the chromatin, two key events in spermatogenesis, are independentof tubulin polymerization. Transitional stages were observed between the granular materialof the blepharoplast and microtubules. Colchicine affected theassembly of the cartwheel structure of the basal bodies lessthan that of the triplets, which were often rudimentary or absent.Autoradiographs were only partially successful because of thefailure to devise a satisfactory method of embedding by freeze-substitution,but there was clear evidence of colchicine binding by nucleiin young spermatocytes. Pteridium aquilinum (L.) Kuhn, bracken, spermatogenesis, colchicine     

Bending growth in fern gametophyte protonema

Filamentous young gametophytes of the fern, Pteridium aquilinum,exhibit a positive phototropism in unilateral light. The displacementof artificial markers demonstrated that this new direction ofgrowth was due to the repositioning of the apical growth tiprather than an increased growth on the dark side. (Received December 16, 1974; )     

The Effect of Systemic Griseofulvin Pre-Treatment on Invasion of Bracken Prothalli by Botrytis cinerea

Griseofulvin pre-treatment of bracken (Pteridium aquilinum)prothalli reduces their susceptibility to invasion by Botrytiscinerea. The number of infection pegs successfully penetratingcell walls is reduced and the size of lesions, where penetrationis achieved, is much reduced. This is partly attributed to reductionin fungal growth-rate by free griseofulvin, but there is alsoa change in host cell-wall reaction to infection. The generalappearance of lesions in griseofulvin-treated prothalli is similarto that of lesions developing on naturally resistant clonesof prothalli. Griseofulvin treatment has no effect on the susceptibilityof prothalli to invasion by Pytkium debaryamtm.     

The Nature of the Membrane Around the Egg of Peteridium aquilinum (L.) Kuhn

The mature egg of Pteridium aquilinum is surrounded by an acetolysis-resistantmembrane. Cytochemical tests indicate that this consists oflipid, possibly in a polymerized form. There is no evidencefor the presence of polysaccharide, protein, lignin, suberin,or sporopollenin. The membrane is believed to be formed frommaterials secreted by the egg itself, and to be analogous tothe inner portion of the megaspore membrane of a gymnospermwhich has a comparable origin and staining properties.     

On separation and identity of fern antheridiogens

Chromatographic studies show that the hormones controlling antheridiuminduction in the fern species Pteridium aquilinum (Polypodiaceae),Anemia phyllitidis and Lygodium japonicum (Schizaeaceae) aredifferent molecular entities. SCHRAUDOLF's report that gibberellic acid induces antheridiain A. phyllitidis and L. japonicum was confirmed. The activityspectrum of GAs towards species of different fern families stronglyresembles that of the native Anemia antheridiogen. However,the native antheridiogens of A. phyllitidis, and of Lygodiumjaponicum, are more species-selective in their action than isGA₃. Preliminary studies have yielded no conclusive evidenceon whether the native antheridiogens are gibberellins. (Received August 21, 1967; )     

Experimental and Analytical Studies of Pteridophytes: XXI. Sterile cultures of an abnormal growth from the gametophyte of bracken

The isolation and growth in sterile culture through sixteenpassages, each of 4 to 6 weeks' duration, of an abnormal growthisolated from a gametophyte of Pteridium aquilinum var. latiusculumis reported, and the nutritional requirements described. The cultures consist of green, photosynthetic, predominantlyfilamentous, but coherent, masses. Prothalli were regeneratedon five occasions during the first two passages only. Outgrowthsof whitish or pale green parenchymatoua tissue occur. Thesepossess a central strand of elongated cells, some of which becomedifferentiated into a core of tracheides. Prothalli of the strain in culture are haploid. When examinedsoon after the initial explantation, the filamentous parts ofthe cultures were diploid, but there has been a subsequent increasein the number of chromosomes, and each cell is now irregularlyaneuploid, with a chromosome number between triploid and tetraploid.     

Spatial Distribution and Reproductive Behaviour of a Triploid Braken (Pteridium aquilinum) Clone in Britain

Chromosome counts of 156 in root tip cells of a bracken plantgrowing in a natural British population confirm the first recordof a triploid in this species. Spore and stomatal measurementssupport the contention of earlier work that cell size in correlatedwith ploidy level in ferns, but the plant is unusual in comparisonwith other odd-numbered polyploids in its degree in its of fertility('good' spore and functional gametophyte production). Two-dimensionalmapping based on isozyme electrophoresis reveal substantialspatial dimensions for the triploid, indicating a plant of considerableantiquity.Copyright 1993, 1999 Academic Press Pteridium aquilinum, bracken, triploid, clone, reproduction, spatial distribution, genetics     

Ethylene Production and Ethylene-induced Apogamous Bud Formation in Nine Gametophytic Strains of Pteridium aquilinum (L.) Kuhn

A comparative study of the abilities of nine gametophytic strainsof Pteridium aquilinum to produce ethylene and to undergo apogamywas conducted. Each gametophytic strain produced ethylene atits characteristic rate and all the strains, except one, formedapogamous buds in response to evolved ethylene which collectedwithin sealed culture vessels or to exogenous ethylene suppliedin a continuous-flow system. The number of apogamous buds producedby each strain was not directly related to the ability of thestrain to produce ethylene, but rather appeared to be dependenton the ability of the gametophytes to respond to ethylene.     

Translocation in Pteridium

The distributions of radioactivity with distance have been mappedin the rachis of Pteridium aquilinum at different times afterapplication of ¹⁴CO₂ to a pinna. Profiles change in shape withtime, from wave to transition and then to diffusion. The apparentdiffusion constant of sucrose may be obtained from transitionand diffusion profiles. Values varied from 2.2 x 10^–3to 3.6 x 10^–2 cm₂ sec^–1. These results are comparedwith those for various angiosperm species.     

A multi-site assessment of the effectiveness of Pteridium aquilinum control in Great Britain

Questions: The objectives of this study were to assess the effect of Pteridium aquilinum (bracken) control treatments, at the national scale, and the impact of restoration practices, at the local scale, on P. aquilinum performance. Hypotheses: 1. Geographical location (locally between and within sites) affects the control of P. aquilinum through time. 2. Are the P. aquilinum control treatments successful at all sites, and if so which ones? 3. The treatments applied at the individual site level to restore vegetation influences the performance of P. aquilinum through time. Location: Four geographically distinct acid grassland and heathland sites infested with P. aquilinum across Great Britain. Methods: Six main-plot, bracken control treatments were applied to all sites with site-specific vegetation restoration treatments. Response variables (P. aquilinum cover, frond length and density) were monitored twice yearly, in June and August between 1993 and 2003. Results: Between- and within-site spatial variation was found, although impact is perhaps less than suggested from shorter-term data. Despite local variation all sites responded similarly to bracken control treatments; asulam treatment resulted in a rapid reduction in frond performance followed by a continued recovery taking approximately ten years to return to untreated values. Cutting treatments tended to have a slower impact at the start but an increasing one over time, especially cutting twice per year. Restoration treatments had a limited impact; the only significant effect in August was grass seeding on frond length at Sourhope. In June only, the plots where sheep were fenced out showed a significant reduction in P. aquilinum cover at Peak. Conclusions: Long-term control of Pteridium aquilinum at all sites and on all measures was best achieved using a continuous cutting treatment, preferably twice per year.     

Mobilisation of phosphorus byPteridium aquilinum

Summary A leaching experiment was designed to assess the ability ofPteridium aquilinum rhizomes to mobilise phosphate from inorganic sources. It was found that in contrast to roots ofCalluna vulgaris Pteridium aquilinum residues effectively released phosphate in an available form from both ground mineral phosphate and a mineral soil.     

Control of Pteridium aquilinum: meta-analysis of a multi-site study in the UK

Background and Aims

A great deal of money is spent controlling invasive weeds as part of international and national policies. It is essential that the funded treatments work across the region in which the policies operate. We argue that experiments across multiple sites are required to validate these programs as results from single sites may be misleading. Here, the control of Pteridium aquilinum (bracken) is used as a test example to address the following four questions. (1) Does the effectiveness of P. aquilinum-control treatments vary across sites? (2) Is the best treatment identified in previous research (cutting twice per year) consistent at all sites, and if not why not? (3) Is treatment performance related to P. aquilinum rhizome mass, litter cover or litter depth at the various sites? (4) Does successful P. aquilinum control influence species richness?

Methods

Pteridium aquilinum‐control treatments were monitored for 10 years using six replicated experiments and analysed using meta-analysis. Meta-regressions were used to explore heterogeneity between sites.

Key Results

The effectiveness of treatments varied between sites depending on the measure used to assess P. aquilinum performance. In general, cutting twice per year was the most successful treatment but on some sites other, less expensive treatments were as good. The effectiveness of treatments at different sites was not related to rhizome mass, but the effectiveness of most applied treatments were inversely related to post-control litter. Effective treatment was also associated with high species richness.

Conclusions

It is concluded that successful development of national weed control programs requires multi-site experimental approaches. Here, meta-analyses demonstrate that variation in effectiveness between sites could be explained in part by pre-specified variables. Reliance on data from a single site for policy formulation is therefore clearly dangerous.Key words: Bracken, Pteridium aquilinum, weed, control, herbicide, litter dynamics, species diversity, meta-analysis     

Ultrastructural Aspects of Sporogenesis in a Fern, Pteridium aquilinum (L.) Kuhn

The meiotic process of sporogenesis in Pteridium is accompaniedby a regular cycle of ultrastructural events. These includethe dedifferentiation and redifferentiation of organelles, andthe elimination and restoration of ribosomes. Although similarin nature to corresponding stages in other land plants, sporogenesisin Pteridium provides several unique features. During prophase the plastids pass through a stage during whichno envelope can be resolved at the periphery of the stroma.They appear to survive this period and there is no evidencethat plastid lineage is broken from primary archesporium tospore. The plastid cycle is accompanied by the presence of theiron-protein complex phytoferritin. The repopulation of the spore cytoplasm with ribosomes, followingthe prophase elimination, is achieved through the agency ofnucleoloid-like bodies. These bodies, however, are not synthesizedwithin the nucleus, but form within membrane-bound regions ofthe early prophase cytoplasm. Prophase is also characterized by the development of nuclearvacuoles, expansions of the perinuclear space, which progressivelyramify through the karyoplasm prior to the dissolution of thenuclear envelope at metaphase I. The significance of these events, their similarities with, anddifferences from, comparable stages of meiosis in other plantsare discussed. Pteridium aquilinum (L.) Kuhn, bracken, meiosis, sporogenesis     

Vegetation development on moorland after control of Pteridium aquilinum with asulam

Abstract. A range of moorland sites in the North York Moors National Park were surveyed where Pteridium aquilinum has been sprayed once with the herbicide asulam between 1 and 7 yr before. The regeneration of both P. aquilinum and the moorland vegetation were studied. The latter was variable and much slower than reported for lowland grassland or heathland, with a large proportion of the developing plant cover consisting of mosses, especially Campylopus introflexus. This slow rate of revegetation was primarily due to the paucity of micro-sites offered for germination in dense P. aquilinum litter, the poor establishment of seedlings in this litter and its slow breakdown. The consequences of this slow and variable development of vegetation to moorland restoration are discussed.     

Biosynthesis of pteroside B in Pteridium aquilinum var. Latiusculum,proof of the sesquiterpenoid origin of the pterosides

Pteroside B was isolated in radioactive form after administration of [2-¹⁴C]mevalonate to Pteridium aquilinum var. latiusculum, demonstrating that the biosynthesis of the aglycone proceeds through the ordinary pathway to sesquiterpenoids. Kuhn-Roth oxidation of the radioactive aglycone was carried out to examine the distribution of the radioactivity among the 3 methyls of the aglycone. The biosynthetic implications of these results are discussed.     

Proteomic Changes in the Stem of Wild <Emphasis Type="Italic">Pteridium aquilinum</Emphasis> During Development

Lignification is one of the most crucial factors affecting the edible value of the stem of wild Pteridium aquilinum. To investigate the probable mechanism of lignification, the changes in protein profiles in the stem of wild P. aquilinum during its development were investigated by means of two-dimensional electrophoresis technology. The two-dimensional electrophoresis results revealed that there were twenty-seven differential proteins, twenty-four proteins of which were identified by MALDI-TOF/TOF. We classified these twenty-four proteins into six functional categories: photosynthesis (8, 33.3 %); respiratory metabolism (4, 16.7 %); stress response and defence (6, 25.0 %); cell structure (1, 4.2 %); phenylpropanoid metabolism (4, 16.6 %) and unclassified protein (1, 4.2 %). According to the functional analysis of these differentially expressed proteins, we concluded that photosynthesis was enhanced during P. aquilinum’s development and sugars generated from photosynthesis were partially metabolized through the glycolysis pathway and phosphopentose pathway, respectively, thus producing the precursors for lignin biosynthesis. The up-regulation of caffeoyl-CoA-O-methyl-transferase and SAM synthetase in abundance and the down-regulation of chalcone synthase can be directly responsible for lignification during stem development. This experiment is useful for understanding the biochemical mechanisms of the lignification process of P. aquilinum during its development.     

Distribution of glycolipids and phospholipids in Pteridium aquilinum

The glycolipids and phospholipids in fronds and rhizomes of Pteridium aquilinum were determined. The total quantity of polar lipid decreased towards the base of the frond, but increased in the storage rhizome. The monogalactosyl diglyceride/digalactosyl diglyceride ratio was 1.8 in the pinnae, 1.0 in the lower petiole and 0.3 in the storage rhizome.