Lecture 14: Gymnosperms (1)

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Lecture 14 Gymnosperms (1)
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Major groups of vascular plants
naked ovule
scale
spores
Ferns
Gymnosperms
Angiosperms
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Gymnosperms - general characteristics
Woody plants (include some of the oldest and
largest known trees). Leaves fan-like,
scale-like or needle-like, often persistent
(sometimes caducous). Flowers unisexual with no
perianth, arranged in infl called cones. The
gymnosperms bear their ovules on flat,
scale- like carpels since the ovules are not
enclosed in an ovary (like in Angiosperms),
they dont have a fruit, and the seeds are
naked. Remember Gymnosperms DO NOT have a
fruit!
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1. Cycadales Cycadaceae

• Ancestral, palm (or fern-) looking.
• Lvs compound, pinnate, persistent.
• Dioecious.
• Genus Cycas C. circinalis

Female inflorescence
male inflorescence
naked ovules
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Cycads have been used as a food source in
Australia for at least 4,300 years
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2. Gynkgoales Ginkgoaceae Ginkgo G. biloba
Trees, no resin canals. Leaves simple closely
packed on stubby short shoots, fan-like, veins
dichotomously branched, emarginate or billobed,
deciduous. Dioecious. Male fl in spike-like
infl. Female fl. reduced to ovules which are
paired on peduncle. Seeds with a fleshy,
bad-smelling outer coat and a hard inner coat.
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Ginkgo biloba (Maidenhair tree)
Female flowers (2 naked ovules on a peduncle)
seeds
2,500 years old Ginkgo Queen in China (photo Wei
Gong)
Male flowers
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Ginkgo - sacred tree

• Confucianism
• a symbol of unity of opposites.
• symbol of eternity and longevity.
• bearer of hope.
• symbol of love.
• protector against fire.

Worshipped like a god in Japan
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Ginkgo-mania
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3. Coniferales
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Taxaceae/Taxus (yews)

• Trees or shrubs no resin canals.
• Leaves needle-like, persistent, alternate,
  2-ranked.
• Dioecious
• Male fl. in small cones.
• Female fl. solitary, naked ovules.
• Seeds with a fleshy outer layer (bright red) and
  hard inner layer.

Taxus canadensis, Canada Yew
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Taxales/Taxaceae/Taxus (yews)
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Taxic Toxic Taxus spp.
The Scythians, a nomadic, warlike tribe tipped
their arrows and spears with extract of Yew tree.
Greek vase of 570 BC
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Poison Cure
Taxol one of the most efficient means against
cancer
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Cupressaceae

• Shrubs trees with resin glands.
• Leaves variable either scale-like opposite, or
  needle-like, in which case they are solitary or
  whorled.
• Monoecious or dioecious
• Male flowers in small cones.
• Female cones with a few flowers in Juniperus 3
  carpels fuse completely in Thuja carpelar scales
  opposite.

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Thuja

• Trees (sometimes shrubs when young).
• Leaves scale-like, opposite and decussate.
• Monoecious.
• Female cones a few pairs of opposite scales.
• T. occidentalis (White cedar, arbor vitae).
• Distribution ON to NS
• Ecology calcareous, to swampy places.

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Juniperus

• Trees or shrubs
• Leaves
• scale-like, opposite and decussate.
• needle-like whorled (3 per node).
• with both needle- and scale-like on the same
  plant.
• Dioecious.
• Female cones 3 carpels perfectly fused at
  maturity, berry-like (but dont forget, this is
  not a fruit!!!!!)

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Juniperus spp. with only needle-like leaves J.
communis (Common juniper)
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Juniperus spp. with both needle- and scale-like
leaves J. virginiana (Eastern red-cedar)
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Taxodium

• Trees with pneumatophores.
• Leaves needle-like, soft, caducous.
• Female cones spherical
• E.g. T. distichum
• (Baldcypress)

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Sequoia

• Giant trees
• Leaves needle-like, persistent.
• Female cones round carpel-scales peltate.
• E.g. S. sempervirens