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Seedless Plants

Seedless Plants. Chapter 26. Plant Adaptations to Land. Cuticle Waxy covering on leaves that helps prevent desiccation Stomata Pores on the surface of leaves that allow CO2 exchange Gametangia Multicellular sex organs which develop multicellular embryos. Alternation of Generations.

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Seedless Plants

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  1. Seedless Plants Chapter 26

  2. Plant Adaptations to Land • Cuticle • Waxy covering on leaves that helps prevent desiccation • Stomata • Pores on the surface of leaves that allow CO2 exchange • Gametangia • Multicellular sex organs which develop multicellular embryos

  3. Alternation of Generations • Gametophyte generation • Haploid • Produces haploid gametes by mitosis • Sporophyte generation • Diploid – begins when haploid gametes fuse • Produces haploid spores by meiosis

  4. Major Groups of Land Plants • Bryophytes • Small, nonvascular • Mosses • Seedless vascular plants • Contain tissues to conduct water and food • Ferns • Gymnosperms • ‘Naked seeds’ • Conifers • Angiosperms • Flowering plants • Most plants are in this group

  5. Bryophytes • Over 15,000 species • Nonvascular – must remain small • Require moist habitats • Three main groups: • Mosses • Liverworts • hornworts

  6. Mosses • No true leaves, stems, or roots due to lack of vascular tissue • Rhizoids – tiny absorptive structures which have a similar function as roots • Upright leaf-like structures • Environmental importance: • Help in soil formation • Sphagnum moss – useful in gardening

  7. Liverworts • Flattened body form called a thallus • Thallus is ‘liver’ shaped • Rhizoids on the underneath side of thallus

  8. Hornworts • Resemble liverworts • Live in disturbed habitats

  9. Seedless Vascular Plants • Ferns, whisk ferns, horsetails, club mosses • Specialized vascular tissue: • Xylem – conducts water • Phloem – conducts dissolved sugars • Allows this group to be larger than the bryophytes

  10. Ferns • Mostly terrestrial • Clearly defined alternation of generations • Rhizome – underground stem which supports a true leaf and roots • Frond – the leaf • Spores are produced on the underside of the frond

  11. Whisk Ferns • The simplest vascular plants • Lack true roots and leaves but have vascularized stems

  12. Horsetails • Have hollow, jointed stems • Were the dominant plants 300 mya • Major contribution to coal deposits • Have true roots, stems, and small leaves • Were used as ‘scouring rushes’

  13. Club Mosses • Also part of modern day coal deposits • Attractive – often used as Christmas wreaths

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