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CHAPTER 38 Reproduction in Flowering Plants PowerPoint PPT Presentation


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CHAPTER 38 Reproduction in Flowering Plants. Chapter 38: Reproduction in Flowering Plants. Many Ways to Reproduce Sexual Reproduction The Transition to the Flowering State. Chapter 38: Reproduction in Flowering Plants. Photoperiodic Control of Flowering Vernalization and Flowering

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CHAPTER 38 Reproduction in Flowering Plants

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CHAPTER 38Reproduction in

Flowering Plants


Chapter 38: Reproduction in Flowering Plants

Many Ways to Reproduce

Sexual Reproduction

The Transition to the Flowering State


Chapter 38: Reproduction in Flowering Plants

Photoperiodic Control of Flowering

Vernalization and Flowering

Asexual Reproduction


Many Ways to Reproduce

  • Almost all flowering plants reproduce sexually, and many also reproduce asexually.

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Many Ways to Reproduce

  • Both sexual and asexual reproduction are important in agriculture.

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Sexual Reproduction

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

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Sexual Reproduction

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

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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

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figure 38-01.jpg

Figure 38.1

Figure 38.1


Sexual Reproduction

  • Pollination enables fertilization in the absence of liquid water.

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Sexual Reproduction

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

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figure 38-04.jpg

Figure 38.4

Figure 38.4


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

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figure 38-06.jpg

Figure 38.6

Figure 38.6


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

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figure 38-07.jpg

Figure 38.7

Figure 38.7


figure 38-08.jpg

Figure 38.8

Figure 38.8


Sexual Reproduction

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

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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


figure 38-10.jpg

Figure 38.10

Figure 38.10


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.

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Photoperiodic Control of Flowering

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

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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


figure 38-11.jpg

Figure 38.11

Figure 38.11


Photoperiodic Control of Flowering

  • Some angiosperms have more complex photoperiodic requirements than short-day or long-day plants, but most are day-neutral.

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Photoperiodic Control of Flowering

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

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figure 38-12.jpg

Figure 38.12

Figure 38.12


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

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figure 38-13a.jpg

Figure 38.13 – Part 1

Figure 38.13 – Part 1


figure 38-13b.jpg

Figure 38.13 – Part 2

Figure 38.13 – Part 2


Photoperiodic Control of Flowering

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

    31


figure 38-14.jpg

Figure 38.14

Figure 38.14


figure 38-15.jpg

Figure 38.15

Figure 38.15


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

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figure 38-16a.jpg

Figure 38.16 – Part 1

Figure 38.16 – Part 1


figure 38-16b.jpg

Figure 38.16 – Part 2

Figure 38.16 – Part 2


Vernalization and Flowering

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

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Asexual Reproduction

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

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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

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Asexual Reproduction

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

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Asexual Reproduction

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

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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

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figure 38-18.jpg

Figure 38.18

Figure 38.18


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.

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