Lesson 7 - Gymnosperms

• Gymnosperms


  Plants with seeds that are not enclosed within a fruit

  
• Gymnosperms


  • Seeds are produced on the open surface of a scale
  • Do not form true flowers or fruits

  
• Gymnosperms


  • Ginkgo
  • Cycas
  • Pinus
• Gymnosperms are woody plants
• Gymnosperms have a well-developed vascular system of xylem and phloem
• Gymnosperms have true roots, stems, and leaves
• Gymnosperms have more efficient and effective vascular systems than seedless plants like ferns
• Gymnosperms can reach large sizes due to secondary growth forming wood
• Divisions of Gymnosperms


  • Cycadophyta
  • Ginkgophyta
  • Coniferophyta/Pinophyta
  • Gnetophyta
• Cycadophyta


  • Habit and leaves similar to palms
  • Trunk does not usually exhibit lateral branching
  • Leaves have circinate vernation
  • Individuals are either male or female
  • Seeds are produced on the lower margins of female sporophylls
  • Pollen releases motile sperm cells into the ovule

  
• Cycadophyta


  • Cycas sp.

  
• Ginkgophyta


  • Native to Asia
  • Have flat fan-shaped leaves
  • Found as ornamentals in temperate countries
• Ginkgophyta


  • Ginkgo biloba
• Coniferophyta/Pinophyta


  • Most important group of gymnosperms
  • Bear their seeds in cones
  • Includes the world's tallest, largest, thickest and oldest living things
• Orders of Coniferophyta/Pinophyta


  • Pinales
  • Pinaceae
  • Araucariaceae
  • Podocarpaceae
  • Sciadopityaceae
  • Cupressaceae
  • Cephalotaxaceae
  • Taxaceae

  
• Coniferophyta/Pinophyta life cycle


  • Male cone releases pollen that is carried on the wind to the female cone
  • Fertilized female gamete develops into an embryo
  • Embryo and integument cells form a seed
  • Seed drops out of cone and germinates
  • Seedling grows into a mature plant that produces cones

  
• Megagametophyte


  • Haploid nutritional tissue found in gymnosperm seeds
  • Produces egg cells that are fertilized to form zygotes
  • Surrounds and nourishes the embryo

  
• Gnetophyta


  • Recent molecular studies placed the gnetums within the conifers
  • Contains Ephedraceae, Gnetaceae, and Welwitschiaceae families

  
• Gnetophyta


  • Ephedra (Mormon Tea)
  • Gnetum
  • Welwitschia
• Ephedra contains alkaloids that can have stimulant effects but also safety concerns
• Philippine Gymnosperms


  • Dacrycarpus imbricatus (Igem)
  • Agathis philippinensis (almaciga)
  • Pinus kesiya (Benguet pine)
  • Cycas sp.

  
• 42 gymnosperm species are found in the Philippines, 15 of which are endemic