1. Plant Structure and Reproduction Double Fertilization

2. Copyright © 2009 Pearson Education, Inc. 31.9 The flower is the organ of sexual reproduction in angiosperms Flowers typically contain four types of highly modified leaves called floral organs –Sepals—enclose and protect flower bud –Petals—showy; attract pollinators –Stamens—male reproductive structures –Carpels—female reproductive structures

3. Stamen Petal Anther Filament Stigma Style Ovary Carpel Ovule Sepal

4. Copyright © 2009 Pearson Education, Inc. Angiosperm (flowering plants) life cycle overview –1. Fertilization occurs in the ovule; –2. the fertilized egg develops into an embryo encased in a seed –3. The ovary develops into a fruit, which protects the seed and aids in dispersal –4. The seed germinates under suitable conditions to produce a seedling, which grows into a mature plant 31.9

5. Ovary, containing ovule Mature plant with flowers, where fertilization occurs Fruit (mature ovary), containing seed Embryo Seed Germinating seed Seedling

6. Copyright © 2009 Pearson Education, Inc. – The male sex cell is a pollen grain –A cell produces 4 spores –Each spore divides to form: a. tube cell – grows down the carpel to the ovary b.generative cell- two nuclei: One fertilizes the egg cell; the other fertilizes the endosperm 31.10

7. Copyright © 2009 Pearson Education, Inc. Double fertilization –One sperm fertilizes the egg to produce a zygote –One sperm fuses with the central cell nuclei to produce endosperm –Endosperm nourishes the developing embryo

8. Development of male gametophyte (pollen grain) Development of female gametophyte (embryo sac) Surviving cell (haploid spore) Ovule Ovary Meiosis Mitosis Anther Cell within anther Meiosis Pollen germinates Four haploid spores Single spore Wall forms Pollination Mitosis (of each spore) Two cells Embryo sac Egg cell Pollen grain released from anther Two sperm in pollen tube Two sperm discharged Pollen tube enters embryo sac Triploid (3n) endosperm nucleus Diploid (2n) zygote (egg plus sperm) Double fertilization occurs