CHAPTER 38 Reproduction in Flowering Plants

1. CHAPTER 38Reproduction in Flowering Plants

2. Chapter 38: Reproduction in Flowering Plants Many Ways to Reproduce Sexual Reproduction The Transition to the Flowering State

3. Chapter 38: Reproduction in Flowering Plants Photoperiodic Control of Flowering Vernalization and Flowering Asexual Reproduction

4. Many Ways to Reproduce • Almost all flowering plants reproduce sexually, and many also reproduce asexually. 4

5. Many Ways to Reproduce • Both sexual and asexual reproduction are important in agriculture. 5

6. Sexual Reproduction • Sexual reproduction promotes genetic diversity in a population, which may give the population an advantage under changing environmental conditions. 6

7. Sexual Reproduction • The flower is an angiosperm’s device for sexual reproduction. 7

8. Sexual Reproduction • Flowering plants have microscopic gametophytes that develop in flowers of the sporophytes. • The megagametophyte is the embryo sac, which typically contains eight nuclei in seven cells. • The microgametophyte is the pollen grain, which delivers two sperm cells to the megagametophyte via a long pollen tube. Review Figure 38.1 8

9. figure 38-01.jpg Figure 38.1 Figure 38.1

10. Sexual Reproduction • Pollination enables fertilization in the absence of liquid water. 10

11. Sexual Reproduction • In self-incompatible species, the stigma rejects pollen from the same plant. Review Figure 38.4 11

12. figure 38-04.jpg Figure 38.4 Figure 38.4

13. Sexual Reproduction • Angiosperms perform double fertilization: • One sperm nucleus fertilizes the egg, forming a zygote • The other unites with the two polar nuclei to form a triploid endosperm nucleus. Review Figure 38.6 12

14. figure 38-06.jpg Figure 38.6 Figure 38.6

15. Sexual Reproduction • The zygote develops into an embryo, remaining quiescent in the seed until conditions are right for germination. • The endosperm is the nutritive reserve upon which the embryo depends at germination. Review Figures 38.7, 38.8 15

16. figure 38-07.jpg Figure 38.7 Figure 38.7

17. figure 38-08.jpg Figure 38.8 Figure 38.8

18. Sexual Reproduction • Flowers develop into seed-containing fruits, which often play important roles in the dispersal of the species. 18

19. The Transition to the Flowering State • For a vegetatively growing plant to flower, an apical meristem in the shoot system must become an inflorescence meristem, which gives rise to bracts and more meristems. • These new meristems may become floral meristems or additional inflorescence meristems. Review Figure 38.10 19

20. figure 38-10.jpg Figure 38.10 Figure 38.10

21. The Transition to the Flowering State • Flowering results from a cascade of gene expression. • Organ identity genes are expressed in floral meristems that give rise to sepals, petals, stamens, and carpels. 21

22. Photoperiodic Control of Flowering • Photoperiodic plants regulate flowering by measuring length of light and dark periods. 22

23. Photoperiodic Control of Flowering • Short-day plants flower when days are shorter than a species-specific critical day length; long-day plants flower when days are longer than a critical day length. Review Figure 38.11 23

24. figure 38-11.jpg Figure 38.11 Figure 38.11

25. Photoperiodic Control of Flowering • Some angiosperms have more complex photoperiodic requirements than short-day or long-day plants, but most are day-neutral. 24

26. Photoperiodic Control of Flowering • The length of the night is what actually determines whether a photoperiodic plant will flower. Review Figure 38.12 26

27. figure 38-12.jpg Figure 38.12 Figure 38.12

28. Photoperiodic Control of Flowering • Interruption of the nightly dark period by a brief exposure to light undoes the effect of a long night. Review Figure 38.13 28

29. figure 38-13a.jpg Figure 38.13 – Part 1 Figure 38.13 – Part 1

30. figure 38-13b.jpg Figure 38.13 – Part 2 Figure 38.13 – Part 2

31. Photoperiodic Control of Flowering • The mechanism of photoperiodic control involves a biological clock and phytochromes. Review Figures 38.14, 38.15 31

32. figure 38-14.jpg Figure 38.14 Figure 38.14

33. figure 38-15.jpg Figure 38.15 Figure 38.15

34. Photoperiodic Control of Flowering • Evidence suggests there is a flowering hormone, called florigen, but it has yet to be isolated from any plant. Review Figure 38.16 34

35. figure 38-16a.jpg Figure 38.16 – Part 1 Figure 38.16 – Part 1

36. figure 38-16b.jpg Figure 38.16 – Part 2 Figure 38.16 – Part 2

37. Vernalization and Flowering • In some plant species, exposure to low temperatures—vernalization—is required for flowering. 37

38. Asexual Reproduction • Asexual reproduction allows rapid multiplication of organisms well suited to their environment. 38

39. Asexual Reproduction • Vegetative reproduction involves modification of a vegetative organ for reproduction. • Stolons (horizontal stems w/roots) • Rhizomes(underground hor. stems) • Bulbs – lilies, onions • Corms - disc-like underground stems • Suckers – shoots produced by roots 39

40. Asexual Reproduction • Some plant species produce seeds asexually by apomixis (female gametophyte produces seeds without pollen fertilization). 40

41. Asexual Reproduction • Agriculturalists use natural and artificial techniques of asexual reproduction to reproduce desirable plants. 41

42. Asexual Reproduction • Horticulturists often graft different plants together to take advantage of favorable properties of both stock(root bearing) and scion(upper graft). Review Figure 38.18 42

43. figure 38-18.jpg Figure 38.18 Figure 38.18

44. Asexual Reproduction • Tissue culture techniques, based on the totipotency of many plant cells, are used to propagate plants asexually, produce virus-free clones of crop plants, and manipulate plants by recombinant DNA technology. 44