• from the Greek: gymnos = naked, sperma = seed
• defining character: seeds not enclosed in fruit
• produce megaspores & microspores,
  usually from sporophylls in strobili
  • multinucleate female gametophyte retained in megasporangium [ovule]
    with nucellus (nutritive tissue)
  • male gametophyte, typically 2-celled, a pollen grain

Pinophyta, conifers

sporophyte generation

• sporophytes are trees (often tall) and shrubs (including krummholtz)
  • from sea level to timberline; equatorial to timberline (tundra)
  • dominant trees in extensive forests of boreal & alpine areas Nⁿ hemisphere
  • oldest known living organisms:
    • bristlecone pine (Pinus longaeva) 4862 yr old when cut in AD 1964
    • bristlecone pine still living was 4723 yr old in 1957
    • dead wood of bristlecone pine has been dated up to 9,000 yr
  • largest known living plants:
    • giant sequoia (Sequoiadendron giganteum) 274.9 ft tall, 102.6 ft circumference
    • giant sequioa 268.8 ft tall, 113.0 ft circumference
• lateral branches arranged spirally; self-pruning
• leaves needle-shaped, round or square; borne on fascicles (short modified shoots)
  in pines Pinus clusters of 2 - 5 (8), clusters round with needles pie-shaped
• needles with solid mesophyll, and resin canals
• leaves deciduous, falling continually a few at a time; live 3 - 5 yrs
  Pinus longaeva leaves up to 30-40 yrs old
• wood [xylem] considered 'soft'
• male strobili (pollen cones) typically small, borne apical on lateral branches near tree top
• female strobili (seed cones) typically large, borne sub-apical on lateral branches lower in canopy

gametophyte generation

• male gametophytes = 4-celled pollen grain, sometimes with wings
  retained in microspore wall, identifiable to genus or species
• female gametophyte retained in megaspore
  produces (1) 2 - 6 archegonia each with one large egg
• more than one egg may be fertilized [fraternal twins]

embryology

• fertilized egg [zygote] retained in archegonium
• fertilized egg may divide into multiple (up to 4) embryos [identical twins]
• competition among multiple embryos normally result is single surviving embryo
• mature embryo
  • stem apical meristem on short stem
  • root apical meristem on long radicle attached to short hypocotyl
  • whorl of cotyledons (average = 8.1)
• embryo embedded in female gametophyte tissue (nutritive)
• surrounded by seed coat (megasporangium tissue)
• on germination, stem and cotyledons covered by seed coat (protective)
  hypocotyl & radical rapidly grow to primary root, branching to secondary roots
• after emerging as seedling, seed coat falls off
  dense primary leaves grow (spirally arranged)
• as lateral branches form, secondary leaves take on 'adult' appearance

Cupressaceae, junipers; Podocarpaceae, podocarps

• do not produce strobili

Araucariaceae, New Zealand pines

• confined to Australia, Tasmania, and New Zealand
• elongated brown male cones at apex of lateral branches near tree top
• round green female cones at apex of lateral branches
• a few develop a fruit-like covering that may almost completely enclose seed
  stomata on upper leaf surfaces (similar to grasses)

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