UNDERSTANDING GYMNOSPERMS

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UNDERSTANDINGGYMNOSPERMS

• JRMG
• 2009-2010

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What are GYMNOSPERMS?

• gymnos - naked spermae - seed
• have seeds (not fruits or flowers)
• developed (Paleozoic Era)
• dominant Mesozoic Era (early )
• heterosporous seed ferns
• Cone bearing plants

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GYMNOSPERMS

• 700 living species
• conifers (such as pines and spruce)
• cycads (such as the sago palm, Cycas revoluta)
• ginkgos (the maidenhair tree, Ginkgo biloba)
• gnetophytes (such as Mormon tea, Ephedra)

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DIVISION GNETOPHYTA

• 70 species (3 genera)
• Welwitschia
• two huge leathery leaves
• Ephedra
• Mormon tree
• Gnetum
• leaves angiosperm-like
• vessels in the xylem
• considered an angiosperm characteristic

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DIVISION GNETOPHYTA

• have some angiosperm-like features
• Cladistic analyses support placement of the
  gnetales (or some portion of them) as outgroups
  for the flowering plants

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Welwitschia mirabilis
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DIVISION CYCADOPHYTA

• pinnate leaves and circinate vernation
• heterosporous
• cones are unisexual
• dioecious
• free-swimming sperm

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DIVISION GINKGOPHYTA

• Ginkgo biloba
• the maidenhair tree
• dioecious
• males are more commonly planted
• females produce seeds that have a nasty odor
• pollination is by wind
• swimming sperm

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DIVISION CONIFEROPHYTA

• Most common gymnosperms
• Pines, spruces, firs, cedars, sequoias, redwood
  and yews
• Can live more than 4000 y.o.

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DIVISION CONIFEROPHYTA

• evergreen
• needle-like leaves
• Needles have a thick cuticle
• sunken stomates
• reduced surface area

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