Biological Sciences
Seedless Vascular Plants
Seedless vascular plants are a group of plants that have specialized vascular tissues for the transport of water, minerals, and nutrients. They reproduce through spores rather than seeds, and include ferns, horsetails, and clubmosses. These plants have a distinct life cycle with alternating generations of sporophyte and gametophyte stages.
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6 Key excerpts on "Seedless Vascular Plants"
eBook - PDF- Samantha Fowler, Rebecca Roush, James Wise(Authors)
- 2016(Publication Date)
- Openstax(Publisher)
survive out of water. Adaptations to life on land include vascular tissues, roots, leaves, waxy cuticles, and a tough outer layer that protects the spores. Land plants include nonvascular plants and vascular plants. Vascular plants, which include seedless plants and plants with seeds, have apical meristems, and embryos with nutritional stores. All land plants share the following characteristics: alternation of generations, with the haploid plant called a gametophyte and the diploid plant called a sporophyte; formation of haploid spores in a sporangium; and formation of gametes in a gametangium. 14.2 Seedless Plants Seedless nonvascular plants are small. The dominant stage of the life cycle is the gametophyte. Without a vascular system and roots, they absorb water and nutrients through all of their exposed surfaces. There are three main groups: the liverworts, the hornworts, and the mosses. They are collectively known as bryophytes. 352 Chapter 14 | Diversity of Plants This OpenStax book is available for free at http://cnx.org/content/col11487/1.9 Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. With the vascular system, there appeared leaves—large photosynthetic organs—and roots to absorb water from the ground. The Seedless Vascular Plants include club mosses, which are the most primitive; whisk ferns, which lost leaves and roots by reductive evolution; horsetails, and ferns. 14.3 Seed Plants: Gymnosperms Gymnosperms are heterosporous seed plants that produce naked seeds. They appeared in the Carboniferous period (359–299 million years ago) and were the dominant plant life during the Mesozoic era (251–65.5 million years ago). Modern-day gymnosperms belong to four divisions. The division Coniferophyta—the conifers—are the predominant woody plants at high altitudes and latitudes. Cycads resemble palm trees and grow in tropical climates.
- Cecie Starr, Christine Evers, Lisa Starr, , Cecie Starr, Cecie Starr, Christine Evers, Lisa Starr(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
Nonvascular plants and Seedless Vascular Plants disperse by releasing spores, but seed plants disperse by releasing seeds. A seed consists of an embryo sporo- phyte and food to support it, enclosed within a protective coat. All nonvascular plants and Seedless Vascular Plants have flagellated sperm. These sperm swim through droplets of water in their environment to reach an egg. As a result, these plants can only reproduce in a damp environment. By contrast, seed plants produce pollen grains. A pollen grain is a walled, immature male game- tophyte. Wind or animals can convey pollen grains between plants, so seed plants can reproduce even in dry environments. Figure 15.4 Cross section of a vascular plant leaf, showing some traits that adapt plants to land. stoma (adjustable opening) xylem phloem (vascular tissues) cuticle (layer of waxy secretions) alternation of generations A life cycle that alter- nates between a diploid spore-producing generation (the sporophyte) and a haploid, gamete-producing one (the gametophyte). cuticle Secreted covering at a body surface. In plants it is waxy and helps conserve water. gametophyte Haploid gamete-forming body in a plant life cycle. lignin Compound that stiffens walls of some cells (including xylem) in vascular plants. phloem Vascular tissue that distributes dissolved sugars. plant Multicellular, typically photosynthetic organ- ism; develops from an embryo that forms within the parent plant and is nourished by it. pollen grain Immature male gametophyte of a seed plant. seed Embryo sporophyte of a seed-bearing plant packaged with nutritive tissue inside a protective coat. seed plant Vascular plant that produces seeds; an angiosperm or gymnosperm. sporophyte Diploid spore-forming body in a plant life cycle. stomata Adjustable openings that extend across a plant cuticle and allow gas exchange. vascular plants Plant lineages that have xylem and phloem; include ferns, gymnosperms, and angiosperms.
eBook - ePub- (Author)
- 2008(Publication Date)
- Trade Paper Press(Publisher)
angiosperms (flowering plants) are all vascular plants.vegetative reproduction type of asexual reproduction in plants that relies not on spores, but on multicellular structures formed by the parent plant. Some of the main types are stolons and runners, sucker shoots produced from roots (such as in the creeping thistle Cirsium arvense ), tubers, bulbs, corms, and rhizomes. Vegetative reproduction has long been exploited in horticulture and agriculture, with various methods employed to multiply stocks of plants.wall pressure in plants, the mechanical pressure exerted by the cell contents against the cell wall. The rigidity (turgor) of a plant often depends on the level of wall pressure found in the cells of the stem. Wall pressure falls if the plant cell loses water.wilting loss of rigidity ( turgor) in plants, caused by a decreasing wall pressure within the cells making up the supportive tissues. Wilting is most obvious in plants that have little or no wood.wood hard tissue beneath the bark of many perennial plants; it is composed of water-conducting cells, or secondary xylem, and gains its hardness and strength from deposits of lignin.xerophyte plant adapted to live in dry conditions. Common adaptations to reduce the rate of transpiration include a reduction of leaf size, sometimes to spines or scales; a dense covering of hairs over the leaf to trap a layer of moist air (as in edelweiss); water storage cells; sunken stomata; and permanently rolled leaves or leaves that roll up in dry weather (as in marram grass). Many desert cacti are xerophytes.xylem tissue found in vascular plants, whose main function is to conduct water and dissolved mineral nutrients from the roots to other parts of the plant.Further Reading
Attenborough, David The Private Life of Plants (1995)Bell, Adrian Plant Form. An Illustrated Guide to Flowering Plant Morphology
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 - PDF- Gurnah, Akinloye(Authors)
- 2018(Publication Date)
- Agri Horti Press(Publisher)
This is the reason, why even very experienced botanists equipped with renowned books on classification of the Central European flora will sometimes and in some places fail (Alps). This chapter will deal with the characteristics of flowering plants that produce seed (phanerogames or spermatophytes) only. Many of the structures present in this plant group can be found with other non- flowering plants, too. But mosses, ferns and algae miss some features, like flowers or seeds while others, like roots or leaves exist in an incomplete way or are replaced by other organs. The body of vegetation of many-celled algae (and mosses) is called thallus, that of flowering plants, ferns and fern-like plants (pteridophytes) is called cormus. The latter are therefore summed up as cormophytes. The body of vegetation of a "typical" flowering plant consists of an underground root and a shoot above ground. The shoot is organized into stem and leaves. Each of these basic organs can exist in many variations and these again can be combined in many different ways. The almost unlimited ability of combination is one of the main reasons of the existence of such a high number of species while at the same time, the identification of the relations of the species is aggravated. If seemingly different organs with different functions can be traced back to the same basic organ, they are called homologous. It is also spoken of homology. Contrasting is analogy where organs with a similar look and function have descended from different organs. The Basics Flowering plants, or angiosperms, make up the largest percentage of plant life on earth for a good reason---they reproduce successfully in huge numbers. We grow angiosperms as ornamental flowers, fruits and vegetables, and pull them out of our lawns as weeds. Some, like hybrid roses, need perfect soil and climate conditions to reproduce but others, This ebook is exclusively for this university only. Cannot be resold/distributed.
eBook - PDF- Davis, Z(Authors)
- 2018(Publication Date)
- Agri Horti Press(Publisher)
This ebook is exclusively for this university only. Cannot be resold/distributed. Economic Botany of Angiosperms 242 Land Plants Reproduced in the Fashion of Terns Evolution of Seeds Early land plants reproduced in the fashion of ferns: spores germinated into small gametophytes, which produced sperm. These would swim across moist soils to find the female organs (archegonia) on the same or another gametophyte, where they would fuse with an ovule to produce an embryo, which would germinate into a sporophyte. This mode of reproduction restricted early plants to damp environments, moist enough that the sperm could swim to their destination. Therefore, early land plants were constrained to the lowlands, near shores and streams. The development of heterospory freed them from this constraint.Heterosporic organisms, as their name suggests, bear spores of two sizes– microspores and megaspores. These would germinate to form microgametophytes and megagametophytes, respectively. This system paved the way for seeds: taken to the extreme, the megasporangia could bear only a single megaspore tetrad, and to complete the transition to true seeds, three of the megaspores in the original tetrad could be aborted, leaving one megaspore per megasporangium. The transition to seeds continued with this megaspore being “boxed in” to its sporangium while it germiates. Then, the megagametophyte is contained within a waterproof integuement, which forms the bulk of the seed. The microgametophyte–a pollen grain which has germinated from a microspore–is employed for dispersal, only releasing its desiccation-prone sperm when it reaches a receptive microgametophyte. Lycopods go a fair way down the path to seeds without ever crossing the threshold. Fossil lycopod megaspores reaching 1 cm in diameter, and surrounded by vegetative tissue, are known–these even germinate into a megagametophyte in situ .
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