1. Gymnosperms
Spring 2011

2. Outline Review of land plant phylogeny Characters of seed plants
Gymnosperm phylogeny & diversity
Gnetophytes
Cycads
Gingko
Conifers

3. Review of land plant phylogeny
Green plants (viridophytes)
Land plants (embryophytes)
Vascular plants (tracheophytes)
Seed plants (spermatophytes)
Gymnosperms
Angiosperms

4. Figure 7.8 from the text
Evolution of
wood before
the evolution
of seeds.

5. Figure 7.11 (Pt. 1) from the text

6. Figure 7.12 from the text

7. Spermatophytes (Seed Plants)
“Gymnosperms”
Angiosperms
Flowering Plants
nonmotile sperm
loss of lateral branches
and MORE!
vessel structure
striate pollen
Seed Ferns
[FOSSIL]
double fertilization
nonmotile sperm
eustele
axillary branching
male gametophyte: pollen grain & pollen tube
vascular cambium [secondary xylem (wood) & secondary phloem) & cork cambium (cork)
seed: MANY CHARACTERS! – e.g., heterospory; reduction/retention of megaspore; integument/micropyle; nutritive tissue

8. Characters of seed plants
Eustele
Axillary branching
Wood
Cambia (vascular cambium, cork cambium)
Seed
Heterospory
Megaspore reduction/retention
Integument/micropyle
Nutritive tissue
Male gametophyte
Pollen grain
Pollen tube

9. Characters of seed plants: Eustele
eustele = primary stem vasculature comprising a
single ring of vascular bundles

10. Characters of seed plants: axillary branching

11. Characters of seed plants: cambia
cambia: vascular cambium (wood) & cork cambium (periderm)

12. X-section of woody stem

13. Characters of seed plants: seed
Heterospory
Megaspore reduction/retention
Integument/micropyle
Nutritive tissue

14. Life cycle of most seed-free plants
homospory
Multicellular
Sporophyte
<
embryo
cells in
sporangium
[with sporangia]
Zygote
< 2n
<
alternation of
generations
SYNGAMY
MEIOSIS
< n
<
Spores
Gametes
[egg + sperm]
Multicellular
Gametophyte
<
<
<
[with gametangia:
archegonia + antheridia]

15. Life cycle of seed plants
heterospory
Multicellular
Sporophyte
<
embryo
megasporangia
Zygote
<
microsporangia
< 2n
<
alternation of
generations
SYNGAMY
MEIOSIS
< n
<
microspores
<
sperm
Male Gametophyte
egg
<
[antheridia]
megaspores
<
<
Female Gametophyte
[archegonia]

16. Evolution of the seed
Megaspore reduction:
-reduction to 1 megaspore

17. Evolution of the seed Megaspore retention:
-the one megaspore is retained within
megasporangium, not released

18. Evolution of the seed Evolution of integument/micropyle from
sterile sporophyte tissue

19. Evolution of the seed pollination droplet:
-secreted by young ovule through micropyle
-water + sugars, amino acids (megasporangium)
-adhering pollen grains pulled inside!

20. Evolution of the seed -nutritive tissue from the female gametophyte
-integument becomes the seed coat

21. Figure 7.11 (Pt. 2) from the text

22. Characters of seed plants
male gametophyte
pollen grain = extremely reduced male gametophyte, a few cells
pollen tube – formed by the pollen, grows though sporophytic tissue to deliver sperm cells to egg (in ovule)

23. Characters of seed plants: seed
Adaptive advantages of the seed:
protection (seed coat)
dispersal unit of sexual reproduction
dormancy mechanisms
nutritive tissue – provides energy for young
seedling, aiding in establishment

24. Two major groups of seed plants:
Gymnosperms—not sure of the early evolutionary history of gymnosperms; could be monophyletic or could be paraphyletic
Angiosperms—monophyly supported by many characters including the carpel

25. Gymnosperm Phylogeny
4 monophyletic lineages of gymnosperms

26. Figure 7.15 from the text
Gymnosperms
paraphyletic
Gymnosperms
monophyletic
Gymnosperms
monophyletic
Gymnosperms
paraphyletic

27. Gymnosperm diversity -ca. 15 families, 75-80 genera, ca. 1,000 species
-4 monophyletic lineages
-all woody
-mostly without effective vegetative reproduction
-only tracheids in the xylem (except for gnetophytes,
which also have vessels)
-naked seeds
-relatively slow sexual reproduction
-worldwide but dominant in many colder or arctic
regions
-include the tallest, the most massive, and the longest
living individual plants

28. Major groups of gymnosperms
Gnetophytes
Cycads
Gingko
Conifers

29. Major groups of gymnosperms
Gnetophyta—Gnetophytes or Gnetales
3 extant genera: Ephedra (65 spp.); Gnetum (28
spp.); Welwitschia mirabilis
related to angiosperms?
recent molecular data: a gymnosperm group
defined by many characters, e.g.:
-opposite leaves, similar pollen
-vessel structure (independent of angiosperms)
-nonmotile sperm (independent?)
-double fertilization (independent of angiosperms)
-some with insect pollination

30. Major groups of gymnosperms
Gnetophyta - Gnetophytes
Ephedra (65 spp.)
-common desert shrub
-reduced
scale-like
leaves

31. Major groups of gymnosperms
Gnetophyta – Gnetales
Gnetum (28 spp.)
tropical vines, trees, shrubs with opposite leaves that look like angiosperms!

32. Major groups of gymnosperms
Gnetales – Gnetophytes
Welwitschia mirabilis
-a strange plant native to deserts of Namibia,
sw Africa!
-2 big curly leaves!

33. Major groups of gymnosperms
Cycadophyta – Cycads
squat, unbranched trunk (little wood),
usually pinnately compound leaves
loss of axillary branching
dioecious: male and female plants
male and female strobili (cones)
motile, multiflagellate sperm!
(ancestral)
coralloid roots with nitrogen-fixing
cyanobacteria
Zamia
Cycas

34. Major groups of gymnosperms
Cycadophyta – Cycads
ca. 11 genera (130 spp.)
now restricted distribution
seeds with bright fleshy seed coat--dispersed by plant-eating dinos!

35. A native U.S. cycad:
Zamia floridana

36. Major groups of gymnosperms
Ginkgophytes – Ginkgo
extensive fossil record but…only
1 living species: Ginkgo biloba!
highly branched tree with
well developed wood
deciduous, fan-shaped leaves with
dichotomous venation
dioecious: male and female trees
-male: “cone” with lateral stalks bearing
microsporangia
-female: no cone, axis with 2 ovules
(outer integument layer fleshy)
motile sperm (ancestral)

37. Major groups of gymnosperms
Coniferophyta – Conifers
ca. 600 spp.
once dominant worldwide, displaced by angios
shrubs or small trees, highly branched with
well developed wood
leaves simple, often needle-like or awl-shaped
-pines: in fascicles
non-motile sperm (pollen tube needed)
female (seed-bearing) cones in most

38. Major groups of gymnosperms
Coniferophyta – Conifers
pollen cone or male cone
-microsporangia & modified leaves
seed cone or female cone
-axis with modified leaves (bracts, usually reduced), each subtending seed-bearing scale (modified branch system)
-woody or leathery or fleshy
Pinus
female

39. Major groups of gymnosperms
Coniferophyta – Conifers
seed cone and pine nuts
Stone Pine nuts
[w U.S.]
Korean pine nuts

40. Figure 8.23 from the text
Pinaceae, Taxaceae, Cupressaceae
Conifers

41. Pinaceae Pinus Pollen usually with 2 appendages Picea
Leaves linear to needle-like
Pinus
Resin canals in
wood & leaves
Pinaceae
Pinus
Pinus
Winged seeds
Ovules 2, inverted

42. Pseudotsuga (Douglas fir)
Abies (fir)
Picea (spruce)
Larix (larch)

43. Pinus (pines) -needles in bundles -cone scales thickened at
the tip and often armed
with a prickle

44. Cupressaceae Pollen without appendages Leaves scale-like to linear
Juniperus
Chamaecyparis
Pollen without appendages
Leaves scale-like to linear
Cryptomeria
Juniperus
Cone scales fused to bracts
Microsporangia 2-10 per microsporophyll &
ovules 1-20 per cone scale
Cupressaceae

45. Juniperus (juniper)
Taxodium (bald cypress)
Chamaecyparis

46. Sequoiadendron giganteum
Sequoia sempervirens (redwood)
Sequoiadendron giganteum
(giant sequoia)

47. Taxaceae Taxus Ovules solitary, cones lacking
Seeds with a fleshy, brightly colored aril

48. Podocarpus
Araucariaceae
(Araucaria)