gymnosperms

• Seed plants


  Gymnosperms and angiosperms
• Gymnosperms


  • Naked seeds
  • Exposed sporophylls that usually form cones
  • Cone-bearing plants termed conifers
• Gymnosperms


  • Pine and cycad trees
• Gymnosperm


  Naked seed (From the Greek: gymnos = naked; sperm = seed)
• Gymnosperms


  • More advanced than ferns
  • Do not have spores, they have seeds
  • The seeds lack a protective enclosure
  • Vascular tissue: conducting water and minerals
  • Do not produce fruits
  • No flowers
  • Provide food to their embryo
  • They have a protective seed coat
  • Heterosporous
  • Sporophyte generation is the dominant phase
• Reduced gametophyte


  The gametophytes of seed plants develop within the walls of spores retained within tissues of the parent sporophyte
• Gymnosperms - Male cones

  1. Microsporophylls

  2. Microsporocytes undergo meiosis to produce haploid microspores

  3. Each microspore develops into a pollen grain
• Gymnosperms - Female cones

  1. Megasporophylls

  2. Megasporocytes undergo meiosis to produce haploid megaspores

  3. Megaspores develop into female gametophytes
• Living gymnosperms


  • Cycadophyta (cycads)
  • Gingkophyta (one living species: Ginkgo biloba)
  • Gnetophyta (Gnetum, Ephedra, Welwitschia)
  • Coniferophyta (conifers)
• Phylum Cycadophyta (cycads)


  • Mostly tropical and subtropical
  • c.100 species of living cycads
  • Cycads have flagellated sperm
  • Arose from seedless vascular plants
  • Common during the Jurrassic era
  • 75% of their species are threatened
• Phylum Cycadophyta - Cones

  1. Separate sexes (dioecious)

  2. Microsporophylls and megasporophylls arranged in large cones (up to 30kg)

  3. Pollinated by beetles

  4. 4-6 months from pollination to fertilization

  5. Seeds are highly toxic (Protection against herbivory?)
• Phylum Ginkgophyta (ginkgos)


  • Dioecious (sexes on separate plants)
  • Ginkgo biloba only living species
  • Have flagellated sperm
  • Deciduous fanlike trees
  • Fossils c.170 mya
• Phylum Gnetophyta


  • Three genera (Gnetum, Ephedra and Welwitschia)
  • 76 living species
  • Found in tropical regions but some species live in desert environments
  • Considered advanced because they have angiosperm like traits
  • They have xylem vessels
  • Double fertilization in Ephedra
• Phylum Gnetophyta - Welwitschia mirabilis


  • Single species in Namib desert (c. 20 mm rainfall py)
  • Dioecious
  • 2 straplike leaves up to 2000 years old
  • Taproot c. 5 metres
  • Basal meristem
  • Woody disk
• Phylum Gnetophyta - Genus Gnetum


  • 35 living species
  • Varies from tropical trees, shrubs, and vines
  • Leaves similar to flowering plants
• Phylum Gnetophyta - Genus Ephedra


  • 40 living species
  • Found in arid regions
• Phylum Coniferophyta


  • Evolved c. 300 mya
  • 500 species
  • Tallest and oldest trees
  • Woody plants
  • Mostly evergreen
  • Needle-shaped or flattened leaves
  • Mostly wind-pollinated
• Phylum Coniferophyta


  • Araucaria
  • Metasequoia
  • Picea
  • Pines (Pinus)
• Pines (Pinus)


  • Native to northern hemisphere
  • Adapted to dry areas
  • Thick cuticle
  • Sunken stomata
  • Narrow xylem tracheids
  • Male and female cones on the same tree (monoecious)
  • Wind pollinated
  • Needle-like leaves in bundles
• Pinus longaeva (Bristlecone pine), which is found in the White Mountains of California, is 4,723 years old!