Biological Sciences
Pteridophytes
Pteridophytes are a group of vascular plants that reproduce via spores. They are characterized by their lack of seeds and flowers, and instead produce spores on the underside of their fronds. Pteridophytes include ferns, horsetails, and clubmosses, and are known for their ability to thrive in moist environments.
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7 Key excerpts on "Pteridophytes"
eBook - ePubPlant Systematics
An Integrated Approach, Fourth Edition
- Gurcharan Singh(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
11Families of Pteridophytes
Pteridophytes, Gymnosperms and Angiosperms constitute Tracheophytes, a dominant group of green plants, characterized by the presence of a well-developed branched, independent and dominant sporophyte, with a vascular system consisting of xylem (tracheids-hence the name Tracheophytes, vessels in angiosperms) and phloem (sieve elements, sieve tubes in angiosperms). The group evolved nearly 420 million years ago and is regarded as monophyletic. Pteridophytes, the seedless vascular plants differ from higher Tracheophytes in lacking seed habit and absence of pollen tube, spores developing freely into gametophytes, although few members exhibit heterospory and the reduction of megaspore number to one, forerunner of seed habit.CLASSIFICATION
Pteridophytes form a complex heterogenous group reflecting antiquity and divergent evolutionary clades and have been classified variously. Engler and Prantl recognized Bryophyta and Pteridophyta as two subdivisions of the division Embryophyta Asiphonogama. Cronquist et al. (1966) recognized four groups within Pteridophytes, each given the rank of a division: Psilophyta, Lycopodiophyta, Equisetophyta and PolypodiophytaBold, Alexopoulos and Delevoryas (1987) included the same four group but preferred name Microphyllophyta for Lycopodiophyta and Arthrophyta for Equisetophyta. Recent evidence indicates that Pteridophytes often separated under ‘Ferns and Fern Allies’, form a paraphyletic assemblage of groups, which represent distinct evolutionary lines and are lumped together for convenience. Recent genetic data has shown that Lycopodiophyta are only distantly related to other vascular plants, having radiated evolutionarily at the base of vascular plant clade, whereas Psilophyta and Equisetophyta are much closer to true ferns.Classification of Smith et al.
A more recent classification of Smith et al. (2006), based on morphology as well as molecular data as such excludes Lycopodiophytes from Ferns. The classification recognizes 4 classes, 11 orders and 37 families under ferns. They estimated Peridophytes include nearly 10280 species, 1280 belonging to lycophytes and nearly 9000 to ferns:
- David L. Hawksworth(Author)
- 2003(Publication Date)
- CRC Press(Publisher)
Chapter 3 Ferns and allied plants
Christopher N. Page
ABSTRACT
Pteridophytes (ferns and allied plants) represent a collective group of vascular plants native to Great Britain and Ireland which have been particularly critically studied from the point of view of detailed ranges, species abundance and habitats. Their study has a history spanning well over 150 years. Patterns of change are characterized by complex dynamics of both losses and gains, and these can differ substantially between the different included groups.This account presents a brief overview of this important loss–gain equation set in an overall habitat perspective. It uses fern and fern ally examples to illustrate contrasting situations on the basis of biological evidence. It is concluded that although many of the changes have been, and continue to be, influenced in either their direction, extent or speed of progression by humans, nevertheless these influences should be seen as a dressing, however substantial, to an underlying process of natural change which is an integral part of the progression of post-glacial evolutionary bio-rediversification in our unusually species-depauperated insular pteridophyte flora. It is thus at least as important to allow new opportunities for new taxa to continue to appear, and especially for new hybrids to form, as it is to preserve just the array of species that we already have.1 Introduction
1.1 Scope
The ferns and allied plants (ferns, clubmosses and quillworts, and horsetails – collectively referred to here as the native Pteridophytes) are in a more or less constant state of change. This account presents a brief overview of dynamics and significance of this change within the insular flora of Britain and Ireland. Previous reports of vascular plant change (e.g. Perring 1970, 1974; Harley and Lewis 1984; Rich and Woodruff 1996) have incorporated Pteridophytes along with the much larger group of flowering plants. Rich (Chapter 2
eBook - PDFTropical Rain Forest Ecosystems
Biogeographical and Ecological Studies
- H. Lieth, M.J.A. Werger(Authors)
- 2012(Publication Date)
- Elsevier Science(Publisher)
They may protect the plant from insect herbivory, serve as a source of additional nutrients, or the indurated stems may even serve for water storage (see also Benzing, Ch. 7, and Wallace, Ch. 13). A few Pteridophytes are aquatic including Acrostichum (Fig. 17.5) in swamps and marshes and Isoetes in ephemeral pools or submerged in permanent water bodies. Azolla and Salvinia are floating aquatics, and Ceratopteris often is, although it may also be rooted in wet mud. Among the variety of life-forms of Pteridophytes two are most common. In one, species have a short erect or decumbent stem and a crown of leaves, as in Diplazium, Dryopteris and Polystichum. In the other common form the stem is long-creeping and frequently branched and bears rather widely P T E R I D O P H Y T E S 335 Fig. 17.5. Acrostichum danaeifolium (Pteridaceae) in aquatic border of lowland rain forest, Barro Colorado Island, Panama. (Photo Alice F. Tryon.) spaced leaves. It may be epigeal as in Micro-gramma, Pleopeltis and Polypodium loriceum, or subterraean as in Dennstaedtia, Hypolepis and Pteridium. More unusual is the liana form with a high climbing leaf in Lygodium and Salpichlaena. Several genera have leaves which are scrambling, supported by other vegetation, rather than climb-ing. Examples are Dicranopteris linearis, Eriosorus flexuosus and Odontosoria jenmanii. A high climb-ing stem occurs in Alsophila biformis, Bolbitis species, Lomagramma, Polybotrya and Teratophyl-lum. Trees are the predominent life-form in the Cyatheaceae, with a single erect stem to 10 m or more tall and a crown of large leaves. The tree form also occurs, rarely, in Ctenitis and in Thelypteris. The least common is the shrub form developed especially by Oleandra species with an erect, short, branched stem and often tufted leaves. Another aspect of life-form relates to the part of a plant — roots, stem, leaves — exposed to a particular environment.
eBook - ePub- Patricia Barnes-Svarney, Thomas E. Svarney(Authors)
- 2014(Publication Date)
- Visible Ink Press(Publisher)
Bryophytes —These are the nonvascular plants. Because bryophytes lack a system for conducting water and nutrients, they are restricted in size and live in moist areas close to the ground. Examples of bryophytes are mosses, liverworts, and hornworts and are most often found in moist environments—mainly because they require water to reproduce sexually. (However, species inhabit almost every environment, from hot, dry deserts to the coldest regions of the Antarctica continent.) Overall, they are the second largest group of land plants after flowering plants. They are generally small, compact plants that rarely grow to more than 8 inches (20 centimeters) tall. They have parts that appear leaflike, stemlike, and rootlike and lack vascular tissue (xylem and phloem). Most species have certain structures that help them to retain moisture around their sperm-producing and egg-producing structures and large gametophytes that hold on to sporophytes.Tracheophytes —These are the vascular plants, which are further divided into seedless plants and those that contain seeds. Plants with seeds are divided into flowering and nonflowering groups. Examples of seedless, vascular plants are ferns, horsetails, and club mosses. The cone-bearing conifers are seed-bearing, nonflowering vascular plants. It’s interesting to note that the majority of plants on Earth are seed-bearing, flowering, vascular plants—known as angiosperms.BRYOPHYTES
Why are bryophytes important to the study of early plants?
Some scientists believe bryophytes called liverworts are some of the closest living relatives of early land plants; they are thought to have evolved from freshwater, multicellular, green algae. Fossils of liverwort plants were found in 2010 in the Central Andean Basin of northwest Argentina. The scientists who made the discovery believe that this bryophyte plant—which lacked stems or roots—may be evidence that plants evolved on land ten million years earlier than previously thought. They found spores from the liverwort fossil that dated from between 473 and 471 million years ago, making these very simple plants the oldest land plant remains found to date.
eBook - ePub- Andrew Lack, David Evans(Authors)
- 2021(Publication Date)
- Taylor & Francis(Publisher)
Section P - Spore-bearing vascular plantsP1 EARLY EVOLUTION OF VASCULAR PLANTSKey Notes
The earliest vascular plants
Earliest fossils of land plants, Cooksonia, occur in late Silurian rocks. It had photosynthetic stems but no leaves or roots and no stomata. By early Devonian several genera occur. They were low growing plants less than 50 cm high bearing sporangia at the tips (Rhyniopsida), laterally (Zosterophyllopsida) or in bunches (Psilophyton). Aglaophyton may provide a link with bryophytes.Later developments
There was rapid diversification through the Devonian era with developments of monopodial branching and trees belonging to the lycopsids, ferns and other living groups. Their greatest abundance was in the Carboniferous during which they reduced the CO2 levels by 10 times, cooling and drying the climate.Origins and evolution
Compared with an aquatic environment, land plants require structures to withstand changes in temperature and humidity, wind, rain and desiccation. They require a conducting system for water and nutrients and mechanical strength. Spores are more resistant to desiccation than gametes so sporophytes become the main plant.Life cycle
Fossils are of sporophytes with sporangia having no or limited dehiscence. Fossil gametophytes are little known, but some probable gametophyte fossils have cup-like structures at the stem tips bearing archegonia and antheridia.Homospory and heterospory
Homosporous plants produce one type of spore that germinates to produce a hermaphrodite gametophyte; heterosporous plants have two types of spore, one producing only male gametophytes, the other female. Heterospory has evolved several times. Most early plants were homosporous but heterospory probably appeared early and increased during the Devonian.Related topics
The bryophytes (O2)Clubmosses and quillworts (P2) Horsetails (P3) Ferns (P4) The earliest vascular plants
Vascular plants first appeared probably in the Silurian era (Table 1 ). The oldest fossils are those of Cooksonia (Fig. 1 ) in the Rhyniopsida from late Silurian rocks, a little over 400 million years BP. Fossils of Cooksonia have been found in several places in Europe and North America. These plants had photosynthetic stems 5-8 cm high that branched dichotomously, i.e. into two even branches at each point, but no leaves or roots. Some had rhizomes, horizontal underground stems, and subterranean rhizoids, one cell thick, growing out from the rhizomes or stems that may have absorbed water and anchored the plant. The earliest fossil Cooksonia
eBook - PDFMicrospores Evolution and Ontogeny
Evolution and Ontogeny
- S. Blackmore, R. B. Knox(Authors)
- 2016(Publication Date)
- Academic Press(Publisher)
5 Pteridophyte sporogenesis: a survey of spore wall ontogeny and fine structure in a polyphyletic plant group Bernard Lugardon Laboratoire de Biologie Végétale, Université Paul Sabatier, 31062 Toulouse cedex, France 1 Introduction 95 2 Sporoderm formation and fine structure 96 2.1 Homosporous Filicopsida 2.2 Heterosporous Filicopsida 2.3 Equisetopsida 2.4 Homosporous Lycopsida 2.5 Heterosporous Lycopsida 3 Discussion 113 3.1 Main tapetum and wall features 3.2 Relationships and evolutionary data 4 Conclusion 118 Acknowledgements 119 References 119 1 INTRODUCTION Pteridophytes are the oldest and probably the most diversified branch of vascular plants. Their long and complex history is reflected in the particularly varied features of sporogenesis or microsporogenesis and sporoderm structure. Many subtle studies of sporogenesis phenomena have been made in the course of the last 120 years, one of the first, and perhaps the most fascinating, being that of Tchistiakoff (1874a, b). Tchistiakoff observed the contents of sporangia in simple aqueous medium and related the whole course of sporogenesis, in particular MICROSPORES: EVOLUTION AND ONTOGENY Copyright © 1990 Academic Press Limited ISBN 0-12-103458-5 All rights of reproduction in any form reserved 96 B. Lugardon meticulously describing the successive stages of meiosis, the signifi-cance and importance of which were only to be understood some 30 years later. However, Tchistiakoffs works and, despite more elaborate laboratory techniques, more recent light microscopy studies did not reveal a large number of significant features that have been discovered in the last few decades using high-performance transmission electron microscopy. A survey of modern data on spore ontogeny and sporoderm characteristics in the different groups of Pteridophytes is given here.
eBook - ePubPhytochemistry of Australia's Tropical Rainforest
Medicinal Potential of Ancient Plants
- Cheryll J. Williams(Author)
- 2021(Publication Date)
- CSIRO PUBLISHING(Publisher)
This drawing depicts the leafless above-ground stems and sporangia (spore-forming organs) growing from branching rhizomes (underground stems). Intriguingly, the fossil has preserved the remains of three different fungal endophytes [ 2 ] (image licensed under the public domain via Wikimedia Commons). The next major evolutionary step for the flora involved a diverse category of plants, the gymnosperms (conifers, cycads, Gnetales and Ginkgoaceae). THE AGE OF THE Pteridophytes The Carboniferous period (359–299 mya) saw the proliferation of ferns, bryophytes and their relatives across the globe. Today only seven families survive whose heritage can be traced back to fossil records of the period – and all are found in Australia’s northern tropical rainforest. Only the more extensive rainforests of New Guinea hold greater diversity: ‘The Wet Tropics of Queensland is therefore one of the most significant centres of evolutionary diversity and survival for the most primitive and relict members of ancestral or ancient orders of spore-producing plants. As such the fern assemblages contribute the earliest chapter to one of the most complete living records of the evolution of land plants’ [ 3 ]. This genetic diversity is important in international terms. Overall there are 36 fern families across the globe, 31 of which are present in the Wet Tropics. Indeed, the greatest diversity of ferns in Australia are found here (250 native species in 111 genera), representing an exceptionally high proportion of the native genera (88%) and species (64%), with 46 species restricted to the area. Of the five fern genera that are endemic to Australia, four are present in the northern Queensland rainforest
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