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Nonvascular Plants: Mosses, Liverworts, and Hornworts (Division…

- - - - perennial
      - occuring in all parts of the world
      - in almost every environment
  - - - innermost cortex cells
        
        conduct water/ dissolved minerals
        
        elongated cells
        
        no cyctoplasm
        
        end walls partially digested
    - - cells that resemble sieve cells
        
        elongate
        
        lack nuclei
        
        retain cytoplasm
    - - along exterior of stems
        
        leaves are small
        
        act as capillary channels
        
        rhizoids located base of stem
        
        trichome-like structure
        
        small/ multicellular
        
        penetrate substrate surface
        
        do not absorb water/ minerals
        
        lack chloroplasts
        
        reddish walls
        
        form narrow spaces
    - - begins when a spore germinates
      - sends out long, slender chlorophyllous cell
      - produces branched system of similar cells
        
        resembles filamentous green alga
        
        distinguished by numerous small chloroplasts
        
        entire network
      - protonema
        
        undergoes mitosis
    - - gametophore
        
        produces gametangia
      - all mosses oogamous
      - small biflagellate sperm cells
        
        produced in microgametangia
        
        called antheridia
        
        short stalk
        
        outer layer of sterile cells
      - large nonmotile egg cells
        
        occur in megagametangia
        
        called archegonia
        
        shaped like vase w/ long neck
        
        single egg located at the base
        
        neck hollow at maturity
      - The Sporophyte Generation
        
        zygote of moss
        
        undergoes a transverse division
        
        basal cell develops into
        
        small bulbous tissue called the foot
        
        interface w/ gametophore
        
        upper cell grows by cell division
        
        absorbs sugars, minerals, and water from gametophore
        
        upper cell grows by cell division
        
        expansion into a simple apical sporangium
        
        called the capsule
        
        operculum
        
        1 more item...
        
        seta
        
        1 more item...
        
        peristome teeth
        
        one or two rows
        
        respond to humidity
        
        traps spores
        
        1 more item...
    - - two critical factors:
        
        small size
        
        lack of conducting tissues
      - several mechanisms compensate
      - for inability of mosses to retain water
      - grow in permanently moist microhabitats
      - tolerant of desiccation
      - desiccated mosses resistant to high/ low temperature
      - and intense ultraviolet (UV) light
- - - - no seeds and vascular tissues.
      - E.g mosses, liverworts, hornworts
    - - vascular tissue is present and seeds are absent.
      - Eg. clubmosses, scouring rushes and ferns.
    - - eg. cycads, conifers and angiosperms.
      - both vascular tissues and seeds are present.
- - - - hetermorphic generations
        
        sportophyte & gametophyte differ structurally
    - - sporangia
      - gametangia
- - - - liverworts
    - - mosses
    - - hornworts
- - - - leafy liverworts
        
        gametophore resembles moss
        
        no midrib
        
        have 2 rounded lobes.
      - thallose liverworts
        
        or heart shaped/ bilaterally symmetrical
        
        flat and ribbon like
        
        air pores
        
        no guard cells
        
        no stomata.
        
        cannot be closed
    - - bisexual
      - or unisexual depending on species
      - antheridiophore
        
        umbrella-shaped outgrowth
      - archegoniophores
        
        apex of radiating fingers
    - - little variability exists
      - basic morphology like that of mosses
      - most liverwort sporophytes:
        
        foot
        
        seta #
        
        clear thin walls
        
        collapse quickly
        
        extremely delicate
        
        calyptra-covered sporangium
        
        elators
        
        spring-shaped walls
        
        uncoil pushing spores out
        
        single elongate cells
- - - - succulent but brittle
        
        winter annuals
        
        live less than 1 year
        
        after fertilization divides longitudinally
  - - - meristem just above the foot
        
        produces new sporangium tissues