Chapter 38: Reproduction in Flowering Plants CHAPTER 38 Reproduction in Flowering Plants

Chapter 38: Reproduction in Flowering Plants

CHAPTER 38Reproduction in Flowering Plants


Chapter 38: Reproduction in Flowering PlantsMany Ways to ReproduceMany Ways to Reproduce

Sexual ReproductionSexual Reproduction

The Transition to the Flowering StateThe Transition to the Flowering State


Chapter 38: Reproduction in Flowering PlantsPhotoperiodic Control of FloweringPhotoperiodic Control of Flowering

Vernalization and FloweringVernalization and Flowering

Asexual ReproductionAsexual Reproduction


Many Ways to Reproduce

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

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Many Ways to Reproduce

• Both sexual and asexual reproduction Both sexual and asexual reproduction are important in agriculture.are important in agriculture.

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Sexual Reproduction

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

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Sexual Reproduction

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

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Sexual Reproduction

• Flowering plants have microscopic Flowering plants have microscopic gametophytes that develop in flowers gametophytes that develop in flowers of the sporophytes. of the sporophytes.

• The megagametophyte is the embryo The megagametophyte is the embryo sac, which typically contains eight sac, which typically contains eight nuclei in seven cells. nuclei in seven cells.

• The microgametophyte is the pollen The microgametophyte is the pollen grain, which delivers two sperm cells grain, which delivers two sperm cells to the megagametophyte via a long to the megagametophyte via a long pollen tube. Review Figure 38.1pollen tube. Review Figure 38.1

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Figure 38.1

Figure 38.1Figure 38.1

figure 38-01.jpg


Sexual Reproduction

• Pollination enables fertilization in the Pollination enables fertilization in the absence of liquid water.absence of liquid water.

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Sexual Reproduction

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

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Figure 38.4


figure 38-04.jpg


Sexual Reproduction

• Angiosperms perform double Angiosperms perform double fertilization: fertilization:

• One sperm nucleus fertilizes the egg, One sperm nucleus fertilizes the egg, forming a zygoteforming a zygote

• The other unites with the two polar The other unites with the two polar nuclei to form a triploid endosperm nuclei to form a triploid endosperm nucleus. Review Figure 38.6nucleus. Review Figure 38.6

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Figure 38.6


figure 38-06.jpg


Sexual Reproduction

• The zygote develops into an embryo, The zygote develops into an embryo, remaining quiescent in the seed until remaining quiescent in the seed until conditions are right for germination. conditions are right for germination.

• The endosperm is the nutritive reserve The endosperm is the nutritive reserve upon which the embryo depends at upon which the embryo depends at germination. Review Figures 38.7, 38.8germination. Review Figures 38.7, 38.8

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Figure 38.7


figure 38-07.jpg


Figure 38.8


figure 38-08.jpg


Sexual Reproduction

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

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The Transition to the Flowering State• For a vegetatively growing plant to For a vegetatively growing plant to

flower, an apical meristem in the shoot flower, an apical meristem in the shoot system must become an inflorescence system must become an inflorescence meristem, which gives rise to bracts meristem, which gives rise to bracts and more meristems. and more meristems.

• These new meristems may become These new meristems may become floral meristems or additional floral meristems or additional inflorescence meristems. Review inflorescence meristems. Review Figure 38.10Figure 38.10

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Figure 38.10


figure 38-10.jpg


The Transition to the Flowering State• Flowering results from a cascade of Flowering results from a cascade of

gene expression. gene expression.

• Organ identity genes are expressed in Organ identity genes are expressed in floral meristems that give rise to floral meristems that give rise to sepals, petals, stamens, and carpels.sepals, petals, stamens, and carpels.

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Photoperiodic Control of Flowering• Photoperiodic plants regulate flowering Photoperiodic plants regulate flowering

by measuring length of light and dark by measuring length of light and dark periods.periods.

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Photoperiodic Control of Flowering • Short-day plants flower when days are Short-day plants flower when days are

shorter than a species-specific critical shorter than a species-specific critical day length; long-day plants flower day length; long-day plants flower when days are longer than a critical when days are longer than a critical day length. Review Figure 38.11day length. Review Figure 38.11

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Figure 38.11


figure 38-11.jpg


Photoperiodic Control of Flowering • Some angiosperms have more Some angiosperms have more

complex photoperiodic requirements complex photoperiodic requirements than short-day or long-day plants, but than short-day or long-day plants, but most are day-neutral.most are day-neutral.

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Photoperiodic Control of Flowering • The length of the The length of the nightnight is what actually is what actually

determines whether a photoperiodic determines whether a photoperiodic plant will flower. Review Figure 38.12plant will flower. Review Figure 38.12

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Figure 38.12


figure 38-12.jpg


Photoperiodic Control of Flowering • Interruption of the nightly dark period Interruption of the nightly dark period

by a brief exposure to light undoes the by a brief exposure to light undoes the effect of a long night. Review Figure effect of a long night. Review Figure 38.1338.13

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Figure 38.13 – Part 1

Figure 38.13 – Figure 38.13 – Part 1Part 1

figure 38-13a.jpg



Figure 38.13 – Part 2Figure 38.13 – Part 2

figure 38-13b.jpg


Photoperiodic Control of Flowering • The mechanism of photoperiodic The mechanism of photoperiodic

control involves a biological clock and control involves a biological clock and phytochromes. phytochromes. Review Figures 38.14, 38.15Review Figures 38.14, 38.15

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Figure 38.14


figure 38-14.jpg


Figure 38.15


figure 38-15.jpg


Photoperiodic Control of Flowering • Evidence suggests there is a flowering Evidence suggests there is a flowering

hormone, called florigen, but it has yet hormone, called florigen, but it has yet to be isolated from any plant. to be isolated from any plant. Review Figure 38.16 Review Figure 38.16

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figure 38-16a.jpg




figure 38-16b.jpg


Vernalization and Flowering• In some plant species, exposure to low In some plant species, exposure to low

temperatures—vernalization—is temperatures—vernalization—is required for flowering.required for flowering.

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Asexual Reproduction

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

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Asexual Reproduction • Vegetative reproduction involves Vegetative reproduction involves

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

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

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

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

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Figure 38.18


figure 38-18.jpg



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

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Chapter 38: Reproduction in Flowering Plants CHAPTER 38 Reproduction in Flowering Plants