1. Plant Reproduction Chapter 31

2. Plants and Pollinators Pollen had evolved by 390 million years ago Pollen had evolved by 390 million years ago Sperm packed inside a nutritious package Sperm packed inside a nutritious package Transferred first by wind currents Transferred first by wind currents Later transferred by insects Later transferred by insects Plants that attracted insect pollinators with flowers had a reproductive advantage Plants that attracted insect pollinators with flowers had a reproductive advantage

3. Angiosperm Life Cycles mature sporophyte male gametophyte female gametophyte DIPLOID HAPLOID fertilization meiosis (within anther) meiosis (within ovary) seed gametes (sperm) microspores megaspores gametes (eggs) (mitosis) Dominant form is the diploid sporophyte In flowers, haploid spores formed by meiosis develop into gametophytes Figure 31.3 Page 538

4. Flower Structure Nonfertile parts Nonfertile parts Sepals Sepals Receptacle Receptacle Fertile parts Fertile parts Male stamens Male stamens Female carpel (ovary) Female carpel (ovary) filamentantherstigmastyleovary receptacle sepal (all sepals combined are the flower’s calyx) OVULE (forms within ovary) petal (all petals combined are the flower’s corolla) STAMEN (male reproductive part) CARPEL (female reproductive part) Figure 31.3 Page 538

5. Kinds of Flowers Perfect flowers Perfect flowers Have both male and female parts Have both male and female parts Imperfect flowers Imperfect flowers Are either male or female Are either male or female Same plant may have both male and female flowers Same plant may have both male and female flowers Sexes may be on separate plants Sexes may be on separate plants

6. Pollen Formation Each anther has four pollen sacs Each anther has four pollen sacs Inside the pollen sacs, cells undergo meiosis and cytoplasmic division to form microspores Inside the pollen sacs, cells undergo meiosis and cytoplasmic division to form microspores Microspores undergo mitosis to form pollen grains Microspores undergo mitosis to form pollen grains

7. Pollen Formation pollen sac anther filament microspore mother cell Meiosis pollen tube sperm nuclei mature male gametophyte stigma style of carpel Diploid Stage Haploid Stage microspores pollen grain Each anther has four pollen sacs Each anther has four pollen sacs Inside pollen sacs, cells undergo meiosis and cytoplasmic division to form microspores Inside pollen sacs, cells undergo meiosis and cytoplasmic division to form microspores Microspores undergo mitosis to form pollen grains Figure 31.6 Page 540

8. Egg Formation All megaspores but one disintegrate All megaspores but one disintegrate It undergoes mitosis three times without cytoplasmic division It undergoes mitosis three times without cytoplasmic division Meiosis in ovule produces megaspores Meiosis in ovule produces megaspores Result is a cell with eight nuclei Result is a cell with eight nuclei Division produces seven-celled female gametophyte Division produces seven-celled female gametophyte One cell is egg, another will form endosperm One cell is egg, another will form endosperm

9. Pollination Transfer of pollen grains to a receptive stigma Transfer of pollen grains to a receptive stigma Pollen can be transferred by a variety of agents Pollen can be transferred by a variety of agents When a pollen grain lands on the stigma it germinates When a pollen grain lands on the stigma it germinates

10. Double Fertilization A pollen tube grows down through the ovary tissue A pollen tube grows down through the ovary tissue It carries two sperm nuclei It carries two sperm nuclei When pollen tube reaches an ovule, it penetrates embryo sac and deposits two sperm When pollen tube reaches an ovule, it penetrates embryo sac and deposits two sperm One fertilizes the egg, other fuses with both nuclei of endosperm mother cell One fertilizes the egg, other fuses with both nuclei of endosperm mother cell

11. seedling (2n) Meiosis ovary (cutaway view) ovary wall stalk an ovule cell embryo sac inside ovule pollen tube endosperm mother cell (n + n) egg (n) Diploid Stage Haploid Stage seed Double Fertilization mature female gametophyte Figure 31.6 Page 540 Events inside Ovule integument

12. Endosperm Formation Occurs only in angiosperms Occurs only in angiosperms Fusion of a sperm nucleus with the two nuclei of the endosperm mother cell produces a triploid (3n) cell Fusion of a sperm nucleus with the two nuclei of the endosperm mother cell produces a triploid (3n) cell This cell will give rise to the endosperm, the nutritive tissue of the seed This cell will give rise to the endosperm, the nutritive tissue of the seed

13. Seeds and Fruits The seed is the mature ovule The seed is the mature ovule The fruit is the mature ovary The fruit is the mature ovary

14. Seed Formation Fertilization of the egg produces a diploid sporophyte zygote Fertilization of the egg produces a diploid sporophyte zygote The zygote undergoes mitotic divisions to become an embryo sporophyte The zygote undergoes mitotic divisions to become an embryo sporophyte Seed: A mature ovule, which encases an embryo sporophyte and food reserves inside a protective coat Seed: A mature ovule, which encases an embryo sporophyte and food reserves inside a protective coat

15. Structure of a Seed Protective seed coat is derived from integuments that enclosed the ovule Protective seed coat is derived from integuments that enclosed the ovule Nutritious endosperm is food reserve Nutritious endosperm is food reserve Embryo has one or two cotyledons Embryo has one or two cotyledons Monocot has one Monocot has one Dicot has two Dicot has two

16. Nourishing the Embryo Dicot embryo Dicot embryo Absorbs nutrients from endosperm Absorbs nutrients from endosperm Stores them in its two cotyledons Stores them in its two cotyledons Monocot embryo Monocot embryo Digestive enzymes are stockpiled in the single cotyledon Digestive enzymes are stockpiled in the single cotyledon Enzymes do not tap into the endosperm until the seed germinates Enzymes do not tap into the endosperm until the seed germinates

17. Fruit: A Mature Ovary Simple fruit Simple fruit Derived from ovary of one flower Derived from ovary of one flower Aggregate fruit Aggregate fruit Derived from many ovaries of one flower Derived from many ovaries of one flower Multiple fruit Multiple fruit Derived from ovaries of many flowers Derived from ovaries of many flowers Accessory fruit Accessory fruit Most tissues are not derived from ovary Most tissues are not derived from ovary

18. Aggregate Fruits Formed from the many carpels of a single flower Formed from the many carpels of a single flower Made up of many simple fruits attached to a fleshy receptacle Made up of many simple fruits attached to a fleshy receptacle Blackberries and raspberries are examples Blackberries and raspberries are examples

19. Multiple Fruits Formed from individual ovaries of many flowers that grew clumped together Formed from individual ovaries of many flowers that grew clumped together Examples: Examples: Pineapple Pineapple Fig Fig

20. Accessory Fruits seed enlarged receptacle ovary tissue receptacle AppleStrawberry ovary Figure 31.8 Page 543

21. Seed Dispersal Fruit structure is adapted to mode of dispersal Fruit structure is adapted to mode of dispersal Some modes of seed dispersal: Some modes of seed dispersal: Wind currents Wind currents Water currents Water currents Animals Animals

22. Asexual Reproduction New roots or shoots grow from extensions or fragments of existing plants New roots or shoots grow from extensions or fragments of existing plants Proceeds by way of mitosis Proceeds by way of mitosis All offspring are genetically identical (unless mutation occurs) All offspring are genetically identical (unless mutation occurs)

23. Natural Clones Forest of quaking aspen in Utah Forest of quaking aspen in Utah 47,000 trees are genetically identical shoots 47,000 trees are genetically identical shoots Roots are all interconnected Roots are all interconnected Oldest known clone Oldest known clone Ring of creosote bushes in Mojave desert is 11,700 years old Ring of creosote bushes in Mojave desert is 11,700 years old

24. Artificial Propagation New plant develops from cuttings or fragments of shoot systems New plant develops from cuttings or fragments of shoot systems African violets and jade plants can be propagated from leaf cuttings African violets and jade plants can be propagated from leaf cuttings Tissue-culture propagation Tissue-culture propagation Tiny plant bits are grown in rotating flasks containing a liquid growth medium Tiny plant bits are grown in rotating flasks containing a liquid growth medium