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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
Chapter 38: Reproduction in Flowering Plants

Many Ways to Reproduce

Sexual Reproduction

The Transition to the Flowering State

chapter 38 reproduction in flowering plants1
Chapter 38: Reproduction in Flowering Plants

Photoperiodic Control of Flowering

Vernalization and Flowering

Asexual Reproduction

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


many ways to reproduce1
Many Ways to Reproduce
  • Both sexual and asexual reproduction are important in agriculture.


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


sexual reproduction1
Sexual Reproduction
  • The flower is an angiosperm’s device for sexual reproduction.


sexual reproduction2
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


sexual reproduction3
Sexual Reproduction
  • Pollination enables fertilization in the absence of liquid water.


sexual reproduction4
Sexual Reproduction
  • In self-incompatible species, the stigma rejects pollen from the same plant. Review Figure 38.4


sexual reproduction5
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


sexual reproduction6
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


sexual reproduction7
Sexual Reproduction
  • Flowers develop into seed-containing fruits, which often play important roles in the dispersal of the species.


the transition to the flowering state
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


the transition to the flowering state1
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.


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


photoperiodic control of flowering1
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


photoperiodic control of flowering2
Photoperiodic Control of Flowering
  • Some angiosperms have more complex photoperiodic requirements than short-day or long-day plants, but most are day-neutral.


photoperiodic control of flowering3
Photoperiodic Control of Flowering
  • The length of the night is what actually determines whether a photoperiodic plant will flower. Review Figure 38.12


photoperiodic control of flowering4
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


photoperiodic control of flowering5
Photoperiodic Control of Flowering
  • The mechanism of photoperiodic control involves a biological clock and phytochromes. Review Figures 38.14, 38.15


photoperiodic control of flowering6
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


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


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


asexual reproduction1
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


asexual reproduction2
Asexual Reproduction
  • Some plant species produce seeds asexually by apomixis (female gametophyte produces seeds without pollen fertilization).


asexual reproduction3
Asexual Reproduction
  • Agriculturalists use natural and artificial techniques of asexual reproduction to reproduce desirable plants.


asexual reproduction4
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


asexual reproduction5
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.