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  Gametophyte generation  Haploid  Produces haploid gametes by mitosis  Sporophyte generation  Diploid – begins when haploid gametes fuse  Produces haploid spores by meiosis

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

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

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

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

Hornworts  Resemble liverworts  Live in disturbed habitats

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

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

Whisk Ferns  The simplest vascular plants  Lack true roots and leaves but have vascularized stems

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’

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