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Ch: 20 Nonvascular Plants: Mosses, Liverworts, and Hornworts…

- - - - smaller
      - more temporary
      - very inconspicuous
      - carry out little photosynthesis
      - look like hairs
    - - larger
      - more prominent generation
  - - - stone walls
      - fences
      - bare rock
- - - - Liverworts
    - - Mosses
    - - Hornworts
- - - - gametophores
        
        leafy stems
        
        leaves
        
        one cell thick
        
        except along midrib and margin
        
        lack of cuticle
        
        no stomata
        
        not homologous of vascular plants
        
        always slender
        
        little tissue differentiation
        
        surface layer only slightly diff from underlying layers
        
        not called epidermis
        
        cortex may be uniform
        
        grow close together
        
        tightly appressed
        
        form dense mounds
        
        grow from an apical meristem that contains a prominent apical cell.
    - - innermost cortex composed of cells called hydroids
        
        conduct water and dissolved minerals
        
        elongated cells
        
        lose cytoplasm when mature
        
        end walls partially digested
        
        not removed entirely
        
        species also contain leptoid cells
        
        resemble sieve cells
        
        elongate
        
        have relatively prominent interconnections w/adjacent cells
        
        lack nuclei at maturatiy
        
        do not retain cytoplasm
        
        majority of mosses lack hydroids and leptoids
        
        water is conducted along exterior of stems by capillary action
    - - begins when spore germinates and sends out long slender chlorophyllous cell
        
        cell undergoes mitosis
        
        produces a branched system of similar cells
        
        protonema
        
        resembles filamentous green algae
        
        can be distinguished by numerous small chloroplasts in each cell
        
        nodules of small cytoplasmic cells form
        
        organize into apical cell
        
        grow upright as a stem w/leaves
        
        perennial
        
        grow exclusively
        
        producing many buds
    - - gametophore produces gametangia
      - mosses all oogamous every species has biflagellate sperm cells and large nonmotile egg cells
      - sperms
        
        produced in microgametangia
        
        antheridia
        
        short stalk
        
        outermost layer of sterile cells
        
        inner mass of cells that differentiate into sperm cells
      - eggs
        
        occur in megagametangia
        
        archegonia
        
        shaped like vase
        
        long neck
        
        hollow neck at maturaity
        
        single egg located at base
      - antheridia and archegonia occur on same gametophore in bisexual species
        
        ex: Funaria, Pottia
      - antheridia and archegonia occur in seperate species
        
        ex: Barvula, Polytrichum, Rhacomitrium
  - - - basal cell
        
        located at bottom of archegonium
        
        develops into a small bulbous tissue
        
        foot
        
        interface w/gametophore
        
        absorbs sugar, minerals, and water
        
        cells are transfer cells
        
        upper cell grows by division and expansion
        
        simple apical sporangium
        
        capsule
        
        3 more items...
        
        seta
        
        between foot and sporangium
        
        narrow stalk
    - - apex differentiates into cap-like lid
        
        operculum
        
        seperates from rest of sporangium as cells tear apart
        
        results in perisome teeth respond to humidity
        
        bend inward when dry and trap spores when humid
        
        covered by calyptra
        
        layer of cells derived from neck
        
        keep pace with sporophyte at first, then slow
        
        eventually torn away
    - - all spores same size and identical
  - - - thin, incomplete cuticle
        
        if exposed dry in only few minutes
        
        w/out vascular tissues
        
        stems and leaves become desiccated
    - - many grow in permanently moist microhabitats
        
        ex: rain forests, cloud forests, near waterfalls
      - tolerant of desiccation
        
        drying out does not damage them like vascular plants
        
        as long as 30% of weight is water
        
        resistant to high or low temp and intense uv light
        
        ex: Tortula ruralis
      - many thrive at low temps
        
        carry out metabolism at cold temps
      - certain mosses grow on hard impervious surfaces
    - - particularly vascular plants
- - - - gametophote
        
        resembles that of moss
        
        thin leaves on slender stem
        
        grows by apical cell w/3,4,or 5 sides
        
        one uppermost
        
        others embedded
        
        tissue simple parenchyma
        
        leaves typically have two rounded lobes
        
        no midrib
        
        no conducting tissues
        
        arranged in three clearly defined rows
        
        leaves of two rows being much bigger than third
    - - less resemblance to mosses
      - not leafy at all
      - flat and ribbon like or heart shaped
      - bilaterally symmetrical
      - body
        
        thallus
        
        w/out roots, stems, and leaves
        
        stratified and tend to be thicker
        
        many cells contain oil drops
      - gametophore
        
        bisexual
        
        antheridia
        
        archegonia
        
        unisex
        
        depends on species
    - - liverwort protonemata are never as extensive or ramified or long lived as mosses
        
        after few cells produced apical cell is established
        
        growth of gametophore begins
  - - - liverwort sporophytes have a foot, septa, calyptracovered sporangium
        
        septa delicate
        
        composed of clear thin walled cells
        
        cells collapse quickly
        
        lacks columella
        
        cells do not undergo meiosis
        
        differentiate into elaters
      - marchantiales have no septa
        
        sporangium is globose
        
        young bright green and chlorophyllous
        
        no stomata
        
        outer layer streile cells much thinner
- - - - always thin
        
        at least along edges
      - only in center do they become more than four or five cells thick
      - shaped like a ribbon or heart
      - may grow outward irregularly
        
        form disk
      - upper surface in many smooth, some thin
        
        chlorophyllous lamellae grow upward
      - parenchynatous
        
        succulent but brittle
        
        does not tolerate drying
      - internally
        
        numerous chambers
        
        form symbiosis and benefit by receiving nitrogen compounds from Nostoc
      - gametangium
        
        development is distinctive
        
        atheridial initials are not surface cells on gametophyte
        
        instead special mucilage chamber forms near upper surface
        
        cells lining chamber grow into it
        
        become antheridia
        
        chamber expands as antheridia grow
        
        roof breaks
        
        antheridia exposed to environment
      - archegonia are formed from superficial cells
        
        don't completely surround egg
        
        egg lies below short neck
        
        neck canal is surrounded by vegetative thallus
        
        after fertilization zygote divides longitudinally
  - - - new cells pushed upward
        
        differentiate
        
        mature
        
        die
        
        simultaneously being replaced by more cells from basal meristem
        
        at tip sporangium is mature and open
        
        outer layer of sterile celss thick
        
        chlorophyllous
      - long, horn like cylinder
      - 1-2 com long, up to 12 cm in some
      - columella
        
        multicellular
        
        do not have spirally thickened walls