1. The Plant Kingdom: Seed Plants
Chapter 27
The Plant Kingdom: Seed Plants

2. Features of seeds Primary means of reproduction and dispersal of
Gymnosperms
Angiosperms

3. Gymnosperm and angiosperm evolution

4. Features of seeds, cont. Seeds are reproductively superior to spores
Embryonic development is further advanced
Seeds contain an abundant food supply
Each seed has a protective seed coat

5. The life cycle of a pine A pine is a mature sporophyte
Pine gametophytes are small and nutritionally dependent on sporophyte
Pine is heterosporous and, in separate cones, produces
Microspores
Megaspores

6. The life cycle of a pine, cont.
Male cones produce microspores
Microspores develop into pollen grains
Pollen grains carried by air to female cones

7. Male and female cones in Pinus contorta

8. The life cycle of a pine, cont.
Female cones produce megaspores by meiosis
One megaspore develops into a female gametophyte in a megasporangium

9. The life cycle of a pine, cont.
After pollination, pollen tube penetrates megasporangium
Pollen tube reaches egg in the archegonium
After fertilization, zygote develops into embryo

10. Life cycle of pine

11. Features distinguishing gymnosperms from bryophytes and ferns
Vascular plants with seeds
Totally exposed or
On cones
Produce wind-borne pollen grains

12. The four phyla of gymnosperms
Phylum Pinophyta
Phylum Cycadophyta
Phylum Ginkgophyta
Phylum Gnetophyta

13. Conifers

14. Phylum Pinophyta Conifers that produce Most are monoecious Wood Bark
Needles
Seeds in cones
Most are monoecious

15. Phylum Cycadophyta Look like palms or ferns
Dioecious, but reproduce with pollen and seeds in conelike structures
Once numerous, now few members left

16. Cycads
A female coontie produces seed cones

17. Cycads
This female cycad in South Africa has a trunk that reaches a height of about 9 m. Note immense seed cones, to 0.8 m long

18. Phylum Ginkgophyta Sole member is Ginkgo biloba Deciduous Dioceious
Female ginkgo produces seeds directly on branches

19. Branch from a female ginkgo, showing exposed seeds and distinctive leaves

20. Gnetophytes
Consist of three genera
Gnetum
Ephedra
Welwitschia

21. Gnetophytes, cont.
Unique among gymnosperms, sharing traits with angiosperms
Vessel elements in their xylem
Cone clusters resemble flower clusters
Life cycle details resemble those of angiosperms

22. Leaves of Gnetum gnemon resemble those of flowering plants
Male Ephedra has pollen cones clustered at the nodes

23. A specimen of Welwitschia mirabilis living in Namib Desert, Namibia – survives on fog

24. Angiosperms (phylum Magnoliophyta)
Vascular plants that produce flowers and seeds enclosed within a fruit
The most diverse and successful group of plants

25. Angiosperms (phylum Magnoliophyta), cont.
Flower may contain
Sepals
Petals
Stamens
Carpels

26. Angiosperms (phylum Magnoliophyta), cont.
Ovules are enclosed within an ovary
After fertilization
Ovules become seeds
Ovary develops into a fruit

27. Floral structure

28. Life cycle of an angiosperm
Sporophyte generation is dominant
Gametophytes are
Reduced in size
Nutritionally dependent on sporophyte generation

29. Life cycle of an angiosperm, cont.
Heterosporous
Within the flower, they produce
Microspores
Megaspores

30. Life cycle of an angiosperm, cont.
Microspore develops into a pollen grain
Megaspore develops into an embryo sac
Embryo sac contains seven cells with eight nuclei

31. Life cycle of an angiosperm, cont.
Egg cell and central cell with two polar nuclei participate in fertilization
Double fertilization resulting in formation of
Dipoid zygote
Triploid endosperm

32. Life cycle of flowering plants

33. Phylum Magnoliophyta is divided into two classes
Monocots
Dicots

34. Nutritive tissue in their mature seeds is endosperm
Most monocots have
Floral parts in multiples of three
Seeds that each contain one cotyledon
Nutritive tissue in their mature seeds is endosperm

35. Simple pistil

36. Compound pistil

37. Nutritive organs in their mature seeds are the cotyledons
Most dicots have
Floral parts in multiples of four or five
Seeds that each contain two cotyledons
Nutritive organs in their mature seeds are the cotyledons

38. Evolutionary adaptations of flowering plants
Reproduce sexually by forming flowers
After double fertilization, seeds are formed within fruits

39. Evolutionary adaptations of flowering plants, cont.
Flowering plants have
Vessel elements in their xylem
Efficient carbohydrate-conducting sieve tube elements in their phloem
Wind, water, insects, or animals transfer pollen grains

40. Carpel of Drimys piperita

41. Evolution of gymnosperms
Seed plants arose from seedless vascular plants
Progymnosperms were seedless vascular plants
Megaphylls
“Modern” woody tissue

42. Evolution of gymnosperms, cont.
Progymnosperms probably gave rise to conifers
Progymnosperms probably gave rise to seed ferns, too
Seed ferns probably gave rise to cycads and ginkgo

43. Evolution of gymnosperms, cont.
Evolution of gnetophytes is unclear
Flowering plants probably descended from ancient gymnosperms

44. Fossil flower

45. Evolution of gymnosperms, cont.
Ancient gymnosperm have
Leaves with broad, expanded blades
Closed carpels

46. Evolution of gymnosperms, cont.
Flowering plants probably dicots
Amborella is a dicot that may be the nearest living relative to the ancestor of all flowering plants