CHAPTER 38 PLANT REPRODUCTION

1. CHAPTER 38 PLANT REPRODUCTION Angiosperm Reproduction & Biotechnology

2. Floral Organs

3. Sepals and petals are nonreproductive organs. Sepals: enclose and protect the floral bud before it opens; usually green and more leaf-like in appearance. In many angiosperms, the petals are brightly colored to attract pollinators.

4. Stamens: male reproductive organs • Stalk: the filament • Anther: pollen sacs. • The pollen sacs produce pollen.

5. Carpels: female reproductive organs Ovary- base of the carpel Ovules Egg cell Embryo Sac (female gametophyte), i.e., seed Stigma- platform for pollen grain Style- slender neck, connects ovary and stigma

6. The stamens and carpels of flowers contain sporangia, within which the spores and then gametophytes develop. The male gametophytes are sperm-producing structures called pollen grains, which form within the pollen sacs of anthers. The female gametophytes are egg-producing structures called embryo sacs, which form within the ovules in ovaries.

7. Pollination begins the process by which the male and female gametophytes are brought together so that their gametes can unite. Pollination- when pollen released from anthers lands on a stigma. Each pollen grain produces a pollen tube, which grows down into the ovary via the style and discharges sperm into the embryo sac, fertilizing the egg. The zygote gives rise to an embryo. The ovule develops into a seed and the entire ovary develops into a fruit containing one or more seeds. Fruits disperse seeds away from the source plant where the seed germinates.

8. Function of Flowers

9. Complete Versus Incomplete Flowers Complete: possess sepals, petals, stamens, and carpels Incomplete: lack one or more of these components Perfect Versus Imperfect Flowers Perfect: possess both stamens and carpels Imperfect: possess either stamens (staminate) or carpels (carpelate), but not both Classification of Flowers

10. Complete Flower

11. Monoecious: both staminate and carpellate flowers are found together on the same plant (e.g., corn). Dioecious: staminate flowers occur on separate plants from those that carry carpellate flowers (e.g., date palms). Monoecious Versus Dioecious

12. Monoecious

13. Dioecious

14. Angiosperm Life Cycle

15. The development of angiosperm gametophytes involves meiosis and mitosis.

16. The male gametophyte begins its development within the sporangia (pollen sacs) of the anther. Within the sporangia are microsporocytes, each of which will from four haploid microspores through meiosis. Each microspore can eventually give rise to a haploid male gametophyte.

17. A microspore divides once by mitosis and produces a generative cell and a tube cell. The generative cell forms sperm. The tube cell, enclosing the generative cell, produces the pollen tube, which delivers sperm to the egg.

18. Pollen Tubes

19. Pollen Grains • This is a pollen grain, an immature male gametophyte.

20. Barriers to Self-Fertilization • Stamens and carpels may mature at different times. • Self-incompatibility- plant rejects its own pollen • Plant design prevents an animal pollinator from transferring pollen from the anthers to the stigma of the same flower.

21. The Genetic Basis for the Inhibition of Self-Fertilization • S-genes: self-incompatibility gene • If a pollen grain and the carpel’s stigma have matching alleles at the S-locus, then the pollen grain fails to initiate or complete the formation of a pollen tube.

22. Pollen Tube Formation and Double Fertilization

23. Seed Development

24. Release of sugars from the endosperm during germination

25. embryo endosperm

26. Typical Monocot (e.g., corn) endosperm present in substantial quantities in mature seed. cotyledon absorbs nutrients from endosperm during seed germination. Typical Dicot (e.g, garden bean) endosperm completely absorbed into cotyledons before seed maturation. Other Dicots (e.g., castor bean) endosperm only partially absorbed by cotyledons during seed maturation. remainder of endosperm absorbed by cotyledons during germination. Fate of the Endosperm

27. Seed Structure

28. Relationship of the Flower to the Fruit

29. As the seeds are developing from ovules, the ovary of the flower is developing into a fruit, which protects the enclosed seeds and aids in their dispersal by wind or animals. Pollination triggers hormonal changes that cause the ovary to begin its transformation into a fruit. If a flower has not been pollinated, fruit usually does not develop, and the entire flower withers and falls away. The ovary develops into a fruit adapted for seed dispersal

30. Fruit Formation The ovary wall becomes the pericarp, the thickened wall of the fruit Other flower parts wither and are shed. However, in some angiosperms, other floral parts contribute to what we call a fruit. Development of a pea fruit (pod)

31. Protection of the enclosed seed (e.g., pea pods). Facilitating dispersal. wings for wind dispersal (e.g., maple). hocks and barbs for attachment to animal fur or avian feathers (e.g., cocklebur). sweet, fleshy fruit encouraging ingestion and dispersal of seeds by animals (e.g., cherry). Functions of the Fruit

32. Fig. 38-10 Types of Fruits Stigma Style Carpels Petal Stamen Flower Ovary Stamen Stamen Sepal Stigma Ovary (in receptacle) Ovule Ovule Pea flower Raspberry flower Pineapple inflorescence Apple flower Each segment develops from the carpel of one flower Remains of stamens and styles Carpel (fruitlet) Sepals Stigma Seed Ovary Stamen Seed Receptacle Pea fruit Raspberry fruit Pineapple fruit Apple fruit (a) Simple fruit (b) Aggregate fruit (c) Multiple fruit (d) Accessory fruit

33. Function: allows seeds to germinate at the most optimal time. Length of dormancy Signals triggering the end of dormancy. occurrence of water period of cold temperature fire light scarification Seed Dormancy

34. Germination of Bean

35. Germination of a Pea

36. Germination of Corn

37. Asexual and Sexual Reproduction in the Life Histories of Plants

38. Asexual Propagation

39. Shoot or stem cuttings generate roots. Cloning from single leaves. Potato eyes used to generate whole potato plants. Plant tissue culture. Grafting. Asexual Propagation of Plants in Agriculture

40. Plant Tissue Culture: Plant biotechnologists have adopted in vitro methods to create and clone novel plants varieties.

41. Axel N. Erlandson (1884-1964)

42. Injecting foreign DNA into host cells Protoplast fusion Genetic Engineering Applications of Plant Tissue Culture

43. A DNA Gun

44. Protoplasts

45. MonocultureRisks and Benefits Potato blight Phytophthora infestans Irish Potato Famine (1845)

46. Fig. 38-18 Genetically modified rice Ordinary rice

47. Ringspot virus Papya

48. Make plants disease resistant Use less pesticides and herbicides Create plants that are more nutritious Improve crop yields Drought resistance Medicine Bioengineering Latest plant developments

49. Inadvertent consequences: allergies (nuts) Ethics: patents and ownership of genes Herbicide tolerance- fear of producing a herbicide resistant weed that could get out of control Loss of biodiversity Food safety Cutting choices for vegetarians Cross pollination with human food crops Bioengineering Plants Risks

50. Humans as Genetic Engineers