Transcript Understanding Our Environment - McGraw Hill Higher Education

Plant Reproduction and Growth
Chapter 18
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Outline
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Angiosperm Flower
 Structure
 Reproduction
 Life Cycle
 Seeds
 Fruit
 Germination
 Hormones
 Tropisms
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
The Angiosperm Flower
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Developing gametophyte generation
completely enclosed within parent sporophyte.
 Pollen grains develop from microspores.
 Embryo sac develops from megaspore.
Male and female structures usually occur
together in same individual flower.
Reproductive structures are not permanent
parts of adult individual.
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The Angiosperm Flower
Flower Structure
 Composed of Whorls
- Outermost - Sepals (Calyx)
- Second - Petals (Corolla)
- Third - Stamens (Androecium)
 Anther
- Fourth - Carpel (Gynoecium)
 Stigma, Style, Ovary

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Structure of Angiosperm Flower
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Angiosperm Reproduction
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Pollen grains develop from microspores
formed in pollen sacs located in the anther.
Eggs develop in ovules, and each ovule
contains a megaspore mother cell.
 Usually only one mother cell survives.
Pollination - Transferring pollen to stigma.
 Self-Pollination
 Pollinators often drawn to nectar
 Wind
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Angiosperm Reproduction
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Fertilization
 Pollen adheres to stigma and begins to
grow pollen tube that pierces the style, and
eventually reaches ovule.
 Double fertilization - two sperm cells used
forming embryo and endosperm.
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Angiosperm Life Cycle
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Seeds
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In early development of angiosperm embryo,
embryo stops developing and becomes
dormant as a result of drying.
 Outermost covering of ovule develop into
seed coat enclosing dormant embryo and
a stored food source.
- Most metabolic activities cease.
Germination - Resumption of metabolic
activities that leads to growth of mature plant.
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Angiosperm Embryo Development
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Fruit
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During seed formation, flower ovary begins to
develop into fruit.
 Fleshy fruits often dispersed by vertebrates.
- Excretion via solid waste.
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Germination
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Resumption of metabolic activities and
growth often trigged by water.
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Plant Hormones
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Differentiation in plants is largely reversible.
 Following germination, further development
depends on activities of meristematic
tissues, and environmental interaction.
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Plant Hormones
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Hormones are produced in small quantities
and transported to another part of an organism
to stimulate physiological processes.
 Produced in non-specialized tissues.
- Auxin
- Cytokinins
- Gibberellins
- Ethylene
- Abscisic Acid
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Auxin
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Regulates cell growth in plants, such as that
controlling phototropism.
 Cells in sunlight elongate more than those
in shade.
 Synthetic auxins used to control weeds.
- 2,4-D
- 2,4,5-T
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies
Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Other Plant Hormones
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Cytokinins
 Stimulates cell division and determines
course of differentiation.
 Promote growth of lateral buds and inhibit
formation of lateral roots.
Gibberellins
 Play major role in stem elongation.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Other Plant Hormones
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Ethylene
 Gas that hastens fruit ripening.
 Can accelerate abscission of leaves or fruits
damaged by various stressors.
Abscisic Acid
 Stimulates leaves to age rapidly and fall off.
 May induce formation of winter buds.
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Photoperiodism and Dormancy
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Photoperiodism - Mechanism by which
organisms measure seasonal changes in
relative day and night length.
 Flowering Responses
- Long-day plants
- Short-day plants
- Day-neutral plants
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Photoperiodism and Dormancy
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Chemical Basis of Photoperiodism
 Phytochromes
 Flowering Hormones
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Tropisms
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Tropisms - Growth responses of plants to
external stimuli.
 Phototropism - Growth towards directional
sources of light.
 Gravitropism - Stems grow upward and
roots downward.
 Thigmotropism - Response of plants to
touch.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Review
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Angiosperm Flower
 Structure
 Reproduction
 Life Cycle
 Seeds
 Fruit
 Germination
 Hormones
 Tropisms
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies