CHAPTER 38 PLANT REPRODUCTION

1. CHAPTER 38 PLANT REPRODUCTION Sexual 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. Mature pollen grains are entire haploid male gametophyte plants. Microsporangia in anthers produce microsporocytes that undergo meiosis and become haploid microspores. Each microspore undergoes mitosis to produce two-celled male gametophyte plants (pollen grains). One cell is the generative cell while the other is the tube cell. Important Things to Note About Angiosperm Life Cycles

16. Entire mature female gametophyte plants spend their entire lives supported by the parent sporophyte. Megasporangia in ovules produce megasporocytes that each undergo meiosis and become four haploid megaspores. Only one of these four cells become functional megaspores, the remaining three degenerating. Important Things to Note About Angiosperm Life Cycles

17. The haploid nucleus of the megaspore undergoes three mitotic divisions to produce a multinucleate cell with eight haploid nuclei. Cytokinesis divides these nuclei into seven cells: three antipodal cells, two synergids, one egg cell, and one binucleate central cell. Together these cells form the mature female gametophyte or embryo sac. Important Things to Note About Angiosperm Life Cycles

18. Fertilization involves a double fertilization event. After attachment to the stigma, the haploid generative cell of a pollen grain undergoes mitosis to produce two sperm nuclei. The two sperm nuclei migrate down the pollen tube as it elongates through the style to the ovary containing the ovules. One sperm nucleus enters the egg cell; the other enters the binucleate central cell of the female gametophyte. Important Things to Note About Angiosperm Life Cycles

19. The central cell is trinucleate for a while. Fusion of all three haploid nucleus yield one triploid nucleus. Mitosis of the triploid central cell produces the multinucleate triploid endosperm tissue. This endosperm tissue represents a source of stored organic energy to be used by the developing sporophyte embryo (derived from the zygote) and to be used during seed germination. Important Things to Note About Angiosperm Life Cycles

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

21. 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.

22. 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.

23. Pollen Tubes

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

25. 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.

26. 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.

27. Pollen Tube Formation and Double Fertilization

28. Seed Development

29. Release of Sugars from the Endosperm During Germination

30. 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 during 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

31. Seed Structure

32. Relationship of the Flower to the Fruit

33. 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

34. 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)

35. 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

36. Fruits

37. Simple Fruits Aggregate Fruits Multiple Fruits Types of Fruits

38. 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

39. Germination of Bean

40. Germination of a Pea

41. Germination of Corn

42. Genet Concept Asexual and Sexual Reproduction in the Life Histories of Plants

43. Vegetative Reproduction consequence of the existence of meristematic tissues and indeterminate growth in plants typically involves fragmentation Apomixis =production of seeds without fertilization diploid cell in ovule develops into embryo Types of Asexual Reproduction in Plants

44. Asexual Propagation

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

46. Plant Tissue Culture: Cloning from Individual Cells

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

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

49. A DNA Gun

50. Protoplasts