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The Plant Kingdom: Seed Plants

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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

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