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Ch21: Nonvascular plants: mosses, liverworts, hornworts, Concepts, spores…

- - - - one thallus can produce several tubers
  - - - sporangium is a long, horn like cylinder, at the tip the sporangium is mature
- - - - moss gametophores grow from apical meristems with a prominent apical cell
      - leaves are aligned in three rows (young), most have a midrib (costa)
      - almost all mosses: leaves are only one cell layer thick except at middle/along margin
      - moss stems: always slender
      - stem tissue: all called cortex, stomata doesn't occur
    - - hydroids conduct water and dissolve minerals, elongated cells that lose cytoplasm when mature
      - species with hydroids usually have leptoids (kinda like sieve cells)
      - leptoids lack nuclei at maturity, keep cytoplasm
      - the majority of mosses lack hydroids and leptoids, water is transported by capillary action along exterior of stems
        
        rhizoids: base of stems, small, multicellular, penetrate substrate, anchor the stem
    - - cytoplasmic cells form on the protonema, apical cell forms, grows upright (stem w/leaves): gametophore
        
        at some point the gametophore produces gametangia
        
        sperm are produced in microgametangia called antheridia
        
        eggs occur in megagametangia (archegonia)
        
        Occur in the same gametophore in bisexual species
  - - - true epidermis, stomata on base of sporangium
      - operculum: caplike lid (apex of sporangium) separates from the rest of the sporangium as cells are torn apart
        
        cell breaking (elaborate and precise)
        
        results in 1-2 rows of peristome teeth that respond to humidity
        
        apex of sporangium in many species: covered by calyptra (cell layer from the neck of archegonium)
  - - - leaves on moss gametophores have a thin incomplete cuticle
      - many species grow in permanently moist microhabitats (rainforests)
      - several mechanisms compensate for mosses inability to retain water
      - other species are tolerant of desiccation (like lichens)
        
        these mosses are very resistant to high/low temp, intense UV light
        
        many moss species thrive at low temp even below 0 degrees C
        
        mosses can grow on hard surfaces bc they have no roots, or they can grow on the surface of water (depending on species)
- - - - gametophore resembles a moss (except no midrib/conducting tissue)
      - stem tissue is simple parenchyma
      - leaves are arranged in 3 rows, leaves of first 2 rows larger than 3rd
      - gametophore stem grows by an apical cell
    - - flat and ribbonlike (or heart shaped)
      - body is referred to as thallus
        
        a body without roots, stems, leaves
        
        body is stratified, much thicker than leafy
        
        cells are loosely arranged as an aerenchyma with large air chambers (air pores) not stomata
    - - archegoniophores: also stalked, but apex shoots outwards and droops down
      - antheridiophore: male gametophytes of Marchantia may produce umbrella shaped outgrowths
        
        dozens of antheridia grow from the upper surface
        
        if sperm cells are carried to the archegoniophore the egg is fertilized, forming a small sporophyte
  - - - seta is very delicate, many marchantiales have no seta at all
      - sproangium: bright green, chlorophyllous, no stomata. Lacks a columella
      - no peristome teeth
      - some cells dont undergo meiosis, instead differentiating into elaters. All liverworts are homosporous