Plant Reproduction and Growth Lecture Outline PDF

Because learning changes everything. ® Chapter 32 Plant Reproduction and Growth Lecture Outline Essentials of the Living World Seventh Edition George Johnson, Joel Bergh © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw...

Because learning changes everything. ® Chapter 32 Plant Reproduction and Growth Lecture Outline Essentials of the Living World Seventh Edition George Johnson, Joel Bergh © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  32.1 Angiosperm Reproduction 1 Reproduction in flowering plants, the angiosperms, can be asexual or sexual. In stable environments, asexual reproduction may be advantageous. This vegetative reproduction results when new individuals are simply cloned from parts of the parent. Asexual reproduction allows individuals to reproduce with lower investment of energy than sexual reproduction. © McGraw Hill, LLC 2  32.1 Angiosperm Reproduction 2 Forms of vegetative reproduction. Runners are slender stems that grow along the soil surface (strawberry plants). Rhizomes are underground horizontal stems that create a network, giving rise to new shoots (irises, potatoes). Suckers, or sprouts, are produced by roots and give rise to new plants (cherry, apple, raspberry plants). Adventitious plantlets arise from meristematic tissue located in the notches of leaves (Kalanchoë daigremontiana). © McGraw Hill, LLC 3  Figure 32.1: Vegetative reproduction (c) Jerome Wexler/Science Source Access the text alternative for these images © McGraw Hill, LLC 4  32.1 Angiosperm Reproduction 3 Sexual reproduction in plants involves an alternation of generations. The diploid sporophyte generation gives rise to a haploid gametophyte generation, which is enclosed within the tissues of the sporophyte. The male gametophytes are pollen grains that develop from microspores. The female gametophyte is the embryo sac, which develops from a megaspore. These gametophytes are produced in separate, specialized structures of the angiosperm flower. Angiosperm reproductive organs are produced seasonally. © McGraw Hill, LLC 5  32.1 Angiosperm Reproduction 4 Most flowers contain male and female parts. The male parts are called stamens. At the tips of stamens are anthers. The female part is called the carpel. The carpel consists of a lower bulging portion called the ovary, a slender stalk called the style, and a sticky tip called the stigma. Flowers that contain only male or only female parts are known as imperfect. Plants that contain imperfect flowers of both male and female on the same plant are called monoecious. © McGraw Hill, LLC 6  32.1 Angiosperm Reproduction 5 Pollen formation: Inside the anthers are pollen sacs, which contain microspore mother cells. Each microspore mother cell undergoes meiosis to form four haploid microspores. These microspores then undergo mitosis to form pollen grains that contain a generative cell and a tube cell nucleus. The tube cell nucleus forms the pollen tube. The generative cell will later divide to form two sperm cells. © McGraw Hill, LLC 7  32.1 Angiosperm Reproduction 6 Egg formation: In the base of the carpel is the ovary, which contains the ovule. Each ovule contains a diploid megaspore mother cell. Each megaspore mother cell undergoes meiosis to produce four haploid megaspores. Only one megaspore survives to undergo repeated mitotic divisions that produce eight haploid nuclei. These nuclei are enclosed in an embryo sac, where the nuclei are precisely arranged. © McGraw Hill, LLC 8  Figure 32.2: Formation of pollen and egg Access the text alternative for these images © McGraw Hill, LLC 9  32.1 Angiosperm Reproduction 7 Pollination is the process by which pollen is transferred from the anther to the stigma. If pollen from a flower’s anther pollinates the same flower’s stigma, then self-pollination has occurred, which can lead to self-fertilization. © McGraw Hill, LLC 10  32.1 Angiosperm Reproduction 8 Many angiosperms use animals to carry pollen grains from flower to flower. These pollinators may be rewarded for their efforts with food (for example, nectar). Flower color and form have been shaped by evolution. Plants may be colored or shaped in ways that attract certain pollinators. For pollination by animals to be effective, a particular insect or animal must visit plant individuals of the same species. © McGraw Hill, LLC 11  Figure 32.3: Insect pollination (a) PictureNet/Getty Images; (b) manfredxy/Shutterstock © McGraw Hill, LLC 12  32.1 Angiosperm Reproduction 9 In some angiosperms and all gymnosperms, pollen is dispersed by wind and reaches the stigmas passively. The individuals of a given plant species must grow where there is ample wind and grow relatively close together. The flowers of the wind-pollinated angiosperms are small, green, and odorless. © McGraw Hill, LLC 13  32.1 Angiosperm Reproduction 10 Fertilization: Pollen grains adhere to the sticky surface of the stigma and begin to grow a pollen tube. The pollen tube pierces the style and grows until it reaches the ovule in the ovary. When the pollen tube reaches the entry to the embryo sac, it releases two sperm cells. One sperm fertilizes the egg while the other sperm fuses with the polar nuclei to form endosperm. This process of using two sperm cells in fertilization is called double fertilization. © McGraw Hill, LLC 14  32.2 Seeds 1 After fertilization, active cell division forms an organized mass of cells, the embryo. Early in the development of the embryo, the embryo stops developing and becomes dormant as a result of drying. This arrestment of development is usually at a point soon after apical meristems and the seed leaves (called cotyledons) have developed. © McGraw Hill, LLC 15  Figure 32.4: Development in an angiosperm embryo Access the text alternative for these images © McGraw Hill, LLC 16  32.2 Seeds 2 The outer covering of the ovule develops into a seed coat. This layer is relatively impermeable and encloses the dormant embryo within the seed, together with a source of food. Germination, the resumption of metabolic activities leading to growth, cannot take place until water and oxygen reach the embryo. This assures that the seed will germinate when conditions are favorable for a plant’s survival. © McGraw Hill, LLC 17  32.3 Fruit During seed formation, the flower ovary begins to develop into fruit. Fruits form in many ways and are varied in form. Fleshy fruits are normally dispersed by birds and other vertebrates. The animals carry seeds from place to place before excreting them as solid waste. Some fruits are dispersed by wind or by attaching themselves to the fur of mammals or the feathers of birds. Some fruits are dispersed by water. © McGraw Hill, LLC 18  Figure 32.5: Types of fruits and common modes of dispersion (a) Emilio Ereza/Alamy Stock Photo; (b) Jack Dykinga/USDA; (c) Roman Samokhin/Shutterstock; (d) Eric Crichton/Getty Images; (e) image100/Corbis/Getty Images; (f) izanbar/Getty Images Access the text alternative for these images © McGraw Hill, LLC 19  32.4 Germination When a seed encounters conditions suitable for its germination. It first absorbs water. Once the seed coat ruptures, aerobic respiration begins. The roots emerge first. In eudicots, cotyledons emerge from underground along with the stem. In monocots, the coleoptile emerges from underground. © McGraw Hill, LLC 20  32.5 Plant Hormones 1 After germination, the pattern of growth and differentiation in the embryo is repeated indefinitely. However, studies by many botanists showed that entire plants could be regenerated from isolated differentiated plant tissues. A plant’s development depends on activities of the meristematic tissues, interacting with the environment through hormones. © McGraw Hill, LLC 21  32.5 Plant Hormones 2 Differentiation is largely reversible in plants. Some types of differentiated plant cells are capable of expressing their hidden genetic information when provided with suitable environmental signals. Plant hormones control the expression of some plant genes. All hormones in plants are produced in tissues that are not specialized for that purpose and carry out many other functions. © McGraw Hill, LLC 22  32.5 Plant Hormones 3 F. C. Steward successfully regenerated plants from isolated bits of phloem tissue. Figure 32.6: How Steward regenerated a plant from differentiated tissue Access the text alternative for these images © McGraw Hill, LLC 23  32.5 Plant Hormones 4 At least five major kinds of hormones are found in plants. Auxin. Gibberellins. Cytokinins. Ethylene. Abscisic acid. © McGraw Hill, LLC 24  32.6 Auxin 1 Phototropism is the growth of plants toward light. Charles Darwin and his son Francis performed experiments that suggested that a substance caused the plant to bend if exposed to light. The substance was later identified to be auxin. © McGraw Hill, LLC 25  Figure 32.7: The Darwins’ experiment with phototropism Access the text alternative for these images © McGraw Hill, LLC 26  32.6 Auxin 2 Frits Went worked out how auxin controls plant growth. Auxin causes the tissues on the side of the seedling into which it flows to grow more than those on the opposite side. The side of the plant in the shade has more auxin and elongates more, causing the plant to bend towards the light. © McGraw Hill, LLC 27  32.6 Auxin 3 Synthetic auxins are used to control weeds. They work by causing the plant to grow to death, reducing ATP production. 2,4-D weed killer affects broadleaf eudicots. © McGraw Hill, LLC 28  32.7 Photoperiodism and Dormancy 1 Photoperiodism is a mechanism by which organisms measure seasonal changes in relative day and night length. Plants’ flowering responses fall into three basic categories in relation to day length. Long-day plants flower when days become longer in the summer. Short-day plants flower when days become shorter in the fall. Day-neutral plants produce flowers without regard to day length. © McGraw Hill, LLC 29  Figure 32.8: How photoperiodism works in plants Access the text alternative for these images © McGraw Hill, LLC 30  32.7 Photoperiodism and Dormancy 2 Plants have the ability to stop growing altogether when conditions are not favorable. This is called dormancy. In temperate zones, dormancy is generally associated with winter when low temperatures and the freezing of water make it impossible for plant growth. © McGraw Hill, LLC 31  32.8 Tropisms Tropisms are directional and irreversible growth responses to external stimuli. Phototropism is the growth of plants towards light. Gravitropism causes stems to grow upward and roots to grow downward. Thigmotropism is the response of plants to touch. © McGraw Hill, LLC 32  Figure 32.9: Tropism guides plant growth (a) Maryann Frazier/Science Source; (b) Martin Shields/Science Source; (c) PhotoAlto/Odilon Dimier/Getty Images © McGraw Hill, LLC 33  Inquiry & Analysis 1 Irwin and Strauss studied the response of wild radish flower color to selection by pollinators. They compared the frequency of yellow, pink, white, and bronze flowers in two populations of wild radishes. Bees created the first population by visiting flowers based on their color preferences. The scientists produced the second population by hand pollinating flowers with no discrimination due to flower color. © McGraw Hill, LLC 34