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25.4E: The Importance of Seedless Vascular Plants

  • Page ID
    13669
  • Seedless vascular plants provide many benefits to life in ecosystems, including food and shelter and, to humans, fuel and medicine.

    Learning Objectives

    • Explain the beneficial roles of seedless vascular plants

    Key Points

    • Mosses and liverworts provide food and shelter for other organisms in otherwise barren or hostile environments.
    • The level of pollution in an environment can be determined by the disappearance of mosses, which absorb the pollutants with moisture through their entire surfaces.
    • Dried peat moss is used as a renewable resource for fuel.
    • Ferns prevent soil erosion, promote topsoil formation, restore nitrogen to aquatic habitats by harboring cyanobacteria, make good house plants, and have been used as food and for medicinal remedies.
    • Coal, a major fuel source and contributor to global warming, was deposited by the seedless vascular plants of the Carboniferous period.

    Key Terms

    • bioindicator: any species that acts as a biological indicator of the health of an environment
    • pharmacopoeia: an official book describing medicines or other pharmacological substances, especially their use, preparation, and regulation
    • sphagnum: any of various widely-distributed mosses, of the genus Sphagnum, which slowly decompose to form peat; often used for fuel

    The Importance of Seedless Vascular Plants

    Mosses and liverworts are often the first macroscopic organisms to colonize an area, both in a primary succession (where bare land is settled for the first time by living organisms) or in a secondary succession (where soil remains intact after a catastrophic event wipes out many existing species ). Their spores are carried by the wind, birds, or insects. Once mosses and liverworts are established, they provide food and shelter for other species. In a hostile environment, such as the tundra where the soil is frozen, bryophytes grow well because they do not have roots and can dry and rehydrate rapidly once water is again available. Mosses are at the base of the food chain in the tundra biome. Many species, from small insects to musk oxen and reindeer, depend on mosses for food. In turn, predators feed on the herbivores, which are the primary consumers. Some reports indicate that bryophytes make the soil more amenable to colonization by other plants. Because they establish symbiotic relationships with nitrogen-fixing cyanobacteria, mosses replenish the soil with nitrogen.

    At the end of the nineteenth century, scientists observed that lichens and mosses were becoming increasingly rare in urban and suburban areas. Since bryophytes have neither a root system for absorption of water and nutrients, nor a cuticle layer that protects them from desiccation, pollutants in rainwater readily penetrate their tissues; they absorb moisture and nutrients through their entire exposed surfaces. Therefore, pollutants dissolved in rainwater penetrate plant tissues readily and have a larger impact on mosses than on other plants. The disappearance of mosses can be considered a bioindicator for the level of pollution in the environment.

    Ferns contribute to the environment by promoting the weathering of rock, accelerating the formation of topsoil, and slowing down erosion by spreading rhizomes in the soil. The water ferns of the genus Azolla harbor nitrogen-fixing cyanobacteria and restore this important nutrient to aquatic habitats.

    Seedless plants have historically played a role in human life through uses as tools, fuel, and medicine. Dried peat moss, Sphagnum, is commonly used as fuel in some parts of Europe and is considered a renewable resource. Sphagnum bogs are cultivated with cranberry and blueberry bushes. The ability of Sphagnum to hold moisture makes the moss a common soil conditioner. Florists use blocks of Sphagnum to maintain moisture for floral arrangements.

    image

    Plants as a renewable resource for fuel: Sphagnum acutifolium is dried peat moss and can be used as fuel.

    The attractive fronds of ferns make them a favorite ornamental plant. Because they thrive in low light, they are well suited as house plants. More importantly, fiddleheads are a traditional spring food of Native Americans in the Pacific Northwest and are popular as a side dish in French cuisine. The licorice fern, Polypodium glycyrrhiza, is part of the diet of the Pacific Northwest coastal tribes, owing in part to the sweetness of its rhizomes. It has a faint licorice taste and serves as a sweetener. The rhizome also figures in the pharmacopoeia of Native Americans for its medicinal properties and is used as a remedy for sore throat.

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    Fiddlehead ferns as food: A chicken dish with fiddlehead ferns as a side is shown. Native Americans traditionally cook fiddleheads with meals during the spring.

    By far the greatest impact of seedless vascular plants on human life, however, comes from their extinct progenitors. The tall club mosses, horsetails, and tree-like ferns that flourished in the swampy forests of the Carboniferous period gave rise to large deposits of coal throughout the world. Coal provided an abundant source of energy during the Industrial Revolution, which had tremendous consequences on human societies, including rapid technological progress and growth of large cities, as well as the degradation of the environment. Coal is still a prime source of energy and also a major contributor to global warming.

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    Carboniferous period plants: This drawing depicts the tall mosses and tree-like ferns of the Carboniferous period that deposited the large amounts of coal throughout the world.

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