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1. 2 Lecture 8 Outline (Ch. 38) I.Flower Structures II.Life Cycle III.Gametophyte Production IV.Flower Development IV.Pollination V.Fertilization VI.Germination.

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Presentation on theme: "1. 2 Lecture 8 Outline (Ch. 38) I.Flower Structures II.Life Cycle III.Gametophyte Production IV.Flower Development IV.Pollination V.Fertilization VI.Germination."— Presentation transcript:

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2 2 Lecture 8 Outline (Ch. 38) I.Flower Structures II.Life Cycle III.Gametophyte Production IV.Flower Development IV.Pollination V.Fertilization VI.Germination VII.Preparation for next lecture

3 3 Angiosperm Overview Stamen Anther Filament Stigma Carpel Style Ovary Receptacle Sepal Petal (a) Structure of an idealized flower

4 4 Anther Pollen tube Germinated pollen grain (n) (male gametophyte) Ovary Ovule Embryo sac (n) (female gametophyte) Egg (n) Sperm (n) Zygote (2n) Seed Embryo (2n) (sporophyte) Simple fruit Germinating seed Mature sporophyte plant (2n) (b) Simplified angiosperm life cycle Key Haploid (n) Diploid (2n) FERTILIZATION Angiosperm Lifecycle

5 5 Develop in anthers, ovaries Pollen: from microspores inside the anther Within an ovule, a haploid megaspore divides by mitosis - forms the embryo sac, the female gametophyte Angiosperm Gametophytes

6 The megaspores give rise to: A.pollen B.petals C.egg cells D.seeds E.ovaries

7 Model for Flowering (actually, end of ch. 35 in this text) Flowering: adult meristem becoming a floral meristem –Activate or repress floral meristem identity genes 2 key genes: LFY and AP1 –Turn on floral organ identity genes –These define the four concentric whorls Sepal, petal, stamen, and carpel

8 ABC Model 3 classes of floral organ identity genes specify 4 organ types 1.Class A genes alone – Sepals 2.Class A and B genes together – Petals 3.Class B and C genes together – Stamens 4.Class C genes alone – Carpels When any one class is missing, aberrant floral organs occur in predictable positions 8

9 9 ABC Model

10 10 ABC Model

11 Based on the ABC model for flower development, if ‘A’ class genes are missing, what develops? A.sepal, sepal, stamen, carpel B.petal, petal, stamen, carpel C.stamen, petal, petal, stamen D.carpel, stamen, stamen, carpel

12 12 Male structure Female structure

13 13 brings female and male gametophytes together Fertilization (syngamy) is preceded by pollination, the placing of pollen on the stigma of the carpel Angiosperm Pollination One of my favorite pollinator systems:

14 14 Abiotic Pollination by Wind Hazel staminate flowers (stamens only) Hazel carpellate flower (carpels only)

15 15 Pollination by Bees Common dandelion under normal light Common dandelion under ultraviolet light

16 16 Pollination by Moths and Butterflies Moth on yucca flower Anther Stigma

17 17 Pollination by Flies Blowfly on carrion flower Fly egg

18 18 Hummingbird drinking nectar of poro flower Pollination by Birds

19 19 Long-nosed bat feeding on cactus flower at night Pollination by Bats

20 20 The pollen grain produces a pollen tube that extends down the style toward the embryo sac Two sperm are released and effect a double fertilization, resulting in a diploid zygote and a triploid (3n) endosperm Angiosperm Pollination  Fertilization

21 21 Double Fertilization One sperm fuses with the egg – diploid (zygote) One sperm fuses with the two polar nuclei – triploid (endosperm)

22 22 develops into a seed containing a sporophyte embryo and a supply of nutrients The zygote gives rise to an embryo with apical meristems and one or two cotyledons Mitosis of the triploid (3n) endosperm gives rise to a multicellular, nutrient-rich mass that feeds the developing embryo and later (in some plants) the young seedling Angiosperm Seed Formation

23 Double fertilization refers to: A.Two sperm fuse with the egg cell B.Two sperm fuse with the polar nuclei C.One sperm fuses with the egg, one with the polar nuclei D.One sperm fuses with the endosperm, one with the tube cell

24 24 Angiosperm Seed Formation

25 25 The Ovary... develops into a fruit adapted for seed dispersal a fruit is a mature ovary that protects the enclosed seeds and aids in their dispersal via wind, water, or animals

26 26 Coconut Dispersal by Water

27 27 Tumbleweed Dispersal by Wind Winged fruit of maple Dandelion “parachute” Winged seed of Asian climbing gourd

28 28 Dispersal by Animals Seeds carried to ant nest Seeds buried in caches Seeds in feces Barbed fruit

29 29 The Mature Seed The embryo and its food supply enclosed by a hard, protective seed coat The seed enters a state of dormancy In dicots, the embryo has two cotyledons (seed leaves) A monocot embryo has one cotyledon Epicotyl Hypocotyl Cotyledons Radicle Seed coat Endosperm (a) Common garden bean, a eudicot with thick cotyledons Cotyledons Epicotyl Hypocotyl Radicle (b) Castor bean, a eudicot with thin cotyledons (c) Maize, a monocot Scutellum (cotyledon) Pericarp fused with seed coat Endosperm Epicotyl Hypocotyl Coleoptile Radicle Coleorhiza

30 30 Evolutionary Adaptations... the process of germination increases the probability that seedlings will survive Germination begins when seeds imbibe water –this expands the seed, rupturing its coat, and triggers metabolic changes that cause the embryo to resume growth The embryonic root, or radicle, is the first structure to emerge from the germinating seed Next, the embryonic shoot breaks through the soil surface

31 31 (a) Common garden bean Seed coat Radicle Hypocotyl Cotyledon Hypocotyl Epicotyl Foliage leaves Cotyledon Hypocotyl Seed Germination (bean)

32 32 Vegetative Reproduction & Agriculture Humans have devised methods for asexual propagation Cuttings can be taken from many kinds of plants Grafting is a modification of vegetative reproduction from cuttings –A twig or bud from one plant can be grafted onto a plant of a closely related species or a different variety of the same species

33 33 Self-Check Part of plantFunctionLater becomes…Examples: OvaryContains eggs (ovules) Flesh of fruitApples, strawberries, coconut meat Pollen Ovule Integuments Cotyledons Endosperm

34 Things To Do After Lecture 7… Reading and Preparation: 1.Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 2.Ch. 38 Self-Quiz: # 1-4 (correct answers in back of book) 3.Read chapter 38, focus on material covered in lecture (terms, concepts, and figures!) 4.Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1.Compare and contrast methods of pollination and methods of seed dispersal used by angiosperms. 2.Explain the difference between pollination and fertilization. 3.Diagram the parts of an idealized flower with labels. 4.Describe the ABC model of flower development.


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