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Gymnosperms
Pages 389-402; Flora of east Texas Vol I
Ponderosa pines: Big Bend National Park, Texas
Gymnosperms are Seed Plants
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“Gymnosperm” = “Naked Seeds”.
4 of 5 branches of a monophyletic
clade called Seed plants.
Seeds (ovules) not enclosed in a
fruit (carpel), but exposed at
pollination time.
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Seeds may later be enclosed
by fused cone scales– juniper
“berries”, etc.
Always woody (some
angiosperms may be
herbaceous).
What are Seed Plants?
1) Heterosporous Life Cycle--2 kinds of
spores:
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Megaspores → egg-producing
gametophyte (megagametophyte).
Develops inside ovule.
Microspores → sperm-producing
gametophyte (microgametophyte).
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Ovulate (seed) cones
2) Microgametophyte (=pollen) is mobile
(wind).
3) Presence of ovules:
Pollen (male) cones
The Ovule: a Special Sporangium
Megasporangium (nucellus) + integuments.
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Megaspores not released:
Remain in ovule where spore germinates &
female gametophyte forms & produces egg.
Fertilization of the egg is & embryo development
occurs within the ovule.
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Mature ovule with embryo = Seed.
Gametophyte
ovule
Gymnosperm (Pine) Life Cycle:
Sporophyte (2N)
Seed w/
embryo
Ovulate
(female)
cone
Male
cone
Mitosis
Zygote
Fertilization
Pollination
Pollen tube
w/ sperm
2N
1N
Pollen
Gametophyte (1N)
Meiosis
MicroSpores
Megaspore
in ovule
Mitosis
Archegonium
& egg
(flowering plants)
Magnoliophyta
Cycadophyta
Gnetophyta
Ginkophyta
Gnetophyta
Pinophyta
Phylogeny of Seed Plants:
Magnoliophyta
Cycadophyta
Ginkophyta
Pinophyta
Classification of Gymnosperms:
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Four existing lineages:
Gnetophytes, Cycads, Gingkos, & Conifers.
Together, only 840 species, 86 genera, 17 families (p. 389).
But, many familiar & important species (pines, etc).
Division Gnetophyta (P. 389).
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Monophyletic despite variable appearance
of members.
Share several unusual features:
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multiple axillary buds, compound pollen
strobilli (cones), unusual pollen
morphology.
Gnetum
Welwitschia
Ephedra
Gnetophyta, Ephedra, (Ephedraceae)
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p. 389-390
40 species of desert, semi-desert shrubs, vines.
Jointed stems & branches & small scale-like leaves.
1 species native to SW margin of E. Texas, none in
Pineywoods, 6 in TX. (p. 390).
Alkaloid ephedrine.
Ephedra antisyphilitica
Palo Duro canyon St. Park, TX
Ephedra aspera
Big Bend National Park, TX
Gnetophyta,Welwitschia,
(Welwitschiaceae)
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2 ragged, continuously growing strap-like leaves
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Cones (strobili) on rim.
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Native to desert in Namib Desert, S.W. Africa.
Gnetophyta, Gnetum, (Gnetaceae)
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Broad-leaved tropical forest vines & trees.
Roughly 40 species.
Superficially resemble flowering plants.
No Texas natives.
Gnetum
Cycadophyta: (Cycads) p. 400-402
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Palm like / fern like plants, unbranched.
Short woody trunk, pinnately compound leaves.
Large, simple strobili. Dioceous. Insect pollination.
Roughly 145 sp.; mostly tropical & Southern Hemisphere.
Nitrogen-fixing bacteria in coralloid roots.
No Texas natives, but grown here as ornamentals.
Ginkophyta: (p. 402-403)
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Ancient lineage originating in Permian,
widespread in Jurrasic, now mostly extinct.
Free branching Trees, branches with spur
shoots & long shoots.
Fan-shaped leaves with dichotomous venation.
Trees dioecious:
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Stalked ovules with fleshy outer layer.
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Microsporangia in catkin-like structures,
pollen releases motile sperm.
Only Ginkgo biloba exists today:
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Fossils resembling it worldwide in
distribution.
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Now restricted in wild to remote area in S.
China.
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Popular landscape tree in U.S. & Europe
(including Texas).
Gingko leaves
Gingko biloba
Pinophyta (Conifers) p. 391-400
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Trees, shrubs with needle-like, linear, or scale-like leaves.
Conelike ovule-bearing structures (Strobili).
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Compound (several branching) megastrobilus.
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Simple unbranched microstrobilus.
8 families, 68 genera, 629 species, (2 Texas families).
Fossils from late Carboniferous (360-286 MYBP).
5 native Pineywoods species.
Conifer: Larix cajanderi, Kamchatka, Russia
Pinophyta: Pincaceae (Pine Family)
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Vegetative Features
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Scale
Trees, shrubs.
Needle or linear leaves in bundles
(fascicles) on short spur shoots (Pinus)
or alternate along stems.
Reproductive Features
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Ovulate Cones (megastrobili)
– Scales spiral around woody axis.
– 2 ovules on upper surface of scale.
– Bract subtends each scale; bract
not adnate to scale.
– Cones longer than broad.
– Seeds winged.
Bract
Plants Monecious:
Pollen cones (microsrtobili)
– 2-6 microsporangia under scales.
Pollen cones
Pinophyta: Pincaceae (Pine Family)
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Other Features:
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10 genera, 200 species.
Widespread especially northtemperate, boreal & subtropics
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Economically, ecologically most
important gymnosperm family.
Scale
Bract
Pollen cones
Major Pinaceae Genera:
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Pinus: Common in mountains, northern, southern US, Mexico.
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3 Texas Pineywoods species.
Picea (spruce) dominant in boreal and mountain forests
Abies (fir) dominant in boreal and mountain forests.
Pseudotsuga (douglas fir) -major western lumber tree.
Picea mariana forest
in Sascatchewan
Abies
Picea
Pseudotsuga Menziesii
(douglas fir)
An important western USA tree.
Native Pinaceae: longleaf pine
(Pinus palustris)
Native Pinaceae: loblolly pine
(Pinus taeda)
Native Pinaceae: shortleaf pine
(pinus echinata)
Cupressaceae
(Cypress or Redwood Family)
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Vegetative Features:
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Trees, shrubs, often large, long-lived.
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Scale like or small needle leaves,
alternate or opposite.
Reproductive Features:
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Ovulate cones small, round (globular).
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Cone scales adnate to subtending
bracts.
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Dry & woody or fleshy (juniper “berries”
at maturity.
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Plants monoecious or dioecious.
Other Features:
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Roughly 110-130 species.
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Includes redwoods, sequoias,
baldypress & junipers.
Juniperus
Taxodium
Important Cupresaceae Genera:
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Juniperus (juniper).
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J. virginiana native to east Texas.
Thuja (White cedar),
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Northern/ Great Lakes swamps &
lowlands.
Sequoiadendron gigantea: (giant
sequoia) California mountains.
Sequoia sempervirens: redwood
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Coastal mountains, California.
Taxodium: (baldcypress)
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Swamps in southeastern USA.
Sequioiadendron
Native Cupressaceae: baldcypress
(Taxodiuim distichium)
Native
Cupressaceae:
Juniperous virginiana
(eastern red cedar)
Cupressaceae: Coastal Redwood
(California) Sequoia sempervirens:
Other Conifer Families: Taxaceae
Taxus (yew)
Taxus baccata
Other Conifer Families: Araucariaceae
Araucaria angustifolia: (southern Brazil)
Other Conifer Families: Podocarpaceae
Podocarpus totara New Zealand
Podocarpus sellowii Brazil
The End
Version 13.01