1. Plant Reproduction Chapter 30

2. The Plant Kingdom Nearly all are multicellular Eukaryotic Terrestrial Vast majority are photoautotrophs Energy from sun Carbon dioxide from air Minerals dissolved in water

3. Plant Kingdom Adaptations to land Well developed tissue Cuticle Stomata Protection of embryo Alternations of generations Sporophyte Diploid Produces spores by meiosis Reproductive structure

4. Plant Kingdom Gametophyte Haploid Produces gametes Egg and sperm Formed by mitosis Egg and sperm fuse to form zygote Undergoes mitosis Forms sporophyte

5. mitosis zygote (2n) multicelled sporophyte (2n) fertilizationmeiosis gametes (2n) spores (2n) multicelled gametophytes (n) mitosis Diploid Haploid Evolutionary Trend

6. sporophyte’s importance gametophyte’s importance green algaebryophytesfernsgymnospermsangiosperms zygote only, no sporophyte

7. Impacts, Issues Video Imperiled Sexual Partners

8. Plants and Pollinators Pollination Transfer of pollen to the stigma Pollen had evolved by 390 million years ago Sperm packed inside a nutritious package Transferred first by wind currents (abiotic) Later transferred by insects Plants that attracted insect pollinators with flowers had a reproductive advantage

9. Pollinators Pollination vectors Winds Insects Birds Other animals Coevolution with pollinators

10. Hummingbird drinking nectar of columbine flower

11. Long-nosed bat feeding on cactus flower at night

12. Pollinators Visual cues Size, shape, color, pattern Olfactory cues Odors from fruit or flowers Pollinators follow concentration gradient of volatile chemicals to their sources Reinforcements Nectar

13. Bee-attracting flower pattern Pollen Formation

14. Common dandelion under normal light Common dandelion under ultraviolet light

15. Angiosperm Life Cycle Plant life cycles are characterized by the alternation between a multicellular haploid (n) generation and a multicellular diploid (2n) generation Diploid sporophytes (2n) produce spores (n) by meiosis; these grow into haploid gametophytes (n) Gametophytes produce haploid gametes (n) by mitosis; fertilization of gametes produces a sporophyte

16. mature sporophyte male gametophyte female gametophyte DIPLOID HAPLOID fertilization meiosis (within anther) meiosis (within ovary) seed gametes (sperm) microspores megaspores gametes (eggs) (mitosis)

17. In angiosperms, the sporophyte is the dominant generation, the large plant that we see The gametophytes are reduced in size and depend on the sporophyte for nutrients The angiosperm life cycle is characterized by “three Fs”: Flowers Double Fertilization Fruits Angiosperm Life Cycle

18. Flower Structure and Function Flowers are the reproductive shoots of the angiosperm sporophyte they attach to a part of the stem called the receptacle Flowers consist of four floral organs: carpels, stamens, petals, and sepals

19. Flower Structure Nonfertile parts Sepals Receptacle Fertile parts Male stamens 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)

20. Kinds of Flowers Perfect flowers (Complete) Have both male and female parts Monoecious Imperfect flowers (Incomplete) Are either male or female Dioecious

21. Microspores to pollen Pollen Formation

22. Development of Male Gametophytes in Pollen Grains Pollen develops from haploid microspores within the microsporangia, or pollen sacs, of anthers Each microspore undergoes mitosis to produce two cells the generative cell the tube cell A pollen grain consists of the two-celled male gametophyte and the spore wall

23. 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 Inside pollen sacs, cells undergo meiosis and cytoplasmic division to form microspores Microspores undergo mitosis to form pollen grains

24. Megaspores to eggs Egg Formation

25. Meiosis in ovule produces megaspores All megaspores but one disintegrate It undergoes mitosis three times without cytoplasmic division Result is a cell with eight nuclei Cytoplasmic division produces seven-celled female gametophyte 6 cells with 1 nucleus 1 being the egg 1 cell with 2 nuclei Dikaryotic Forms the endosperm

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

27. Pollination

28. Double Fertilization Pollen

29. Double Fertilization After landing on a receptive stigma, a pollen grain produces a pollen tube that extends between the cells of the style toward the ovary It carries two sperm nuclei When pollen tube reaches an ovule, it penetrates embryo sac and deposits two sperm One sperm fertilizes the egg the other combines with the polar nuclei giving rise to the triploid endosperm (3n) nutritive tissue of the seed

30. Polar nuclei Pollen grain Ovule Two sperm Egg Stigma Pollen tube Style Ovary Micropyle Tube nucleus

31. Polar nuclei Polar nuclei Pollen grain Ovule Egg Synergid Two sperm Ovule Two sperm Egg Stigma Pollen tube Style Ovary Micropyle Tube nucleus

32. Zygote (2n) (egg plus sperm) Endosperm nucleus (3n) (two polar nuclei plus sperm) Polar nuclei Polar nuclei Pollen grain Ovule Egg Synergid Two sperm Ovule Two sperm Egg Stigma Pollen tube Style Ovary Micropyle Tube nucleus

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

34. Structure of the Mature Seed The embryo and its food supply are enclosed by a hard, protective seed coat The seed enters a state of dormancy, wherein it stops growing and slows metabolism A mature seed is only about 5–15% water

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

36. Eudicot seed development Nourishing the Embryo

37. Seed Dormancy: An Adaptation for Tough Times Seed dormancy increases the chances that germination will occur at a time and place most advantageous to the seedling The breaking of seed dormancy often requires environmental cues, such as temperature or lighting changes

38. Seed Germination / Seedling Development Germination depends on imbibition, the uptake of water due to low water potential of the dry seed The radicle (embryonic root) emerges first Next, the shoot tip breaks through the soil surface

39. Fruit A fruit develops from the ovary It protects the enclosed seeds and aids in seed dispersal

40. Animation: Fruit Development Right click slide / Select play

41. (b) Aggregate fruit Stamen (a) Simple fruit (c) Multiple fruit (d) Accessory fruit Stamen Ovary Stigma Ovary Stamen Ovary (in receptacle) Ovule Seed Pea flower Pea fruit Raspberry flower Carpels Pineapple inflorescence Raspberry fruit Carpel (fruitlet) Pineapple fruit Apple fruit Each segment develops from the carpel of one flower Flower Style Petal Sepal Apple flower Sepals Seed Remains of stamens and styles Receptacle

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

43. wingseed (in carpel)

44. Dandelion “seeds” (actually one-seeded fruits) Dandelion fruit

46. Ant carrying seed with attached “food body”

47. Advantages and Disadvantages of Asexual vs Sexual Reproduction Asexual reproduction is also called vegetative reproduction Asexual reproduction can be beneficial to a successful plant in a stable environment However, a clone of plants is vulnerable to local extinction if there is an environmental change Sexual reproduction generates genetic variation that makes evolutionary adaptation possible

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