rav65819_ch42_827-850

rav65819_ch42_827-850 - ; 42 chapter Plant Reproduction...

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chapter Plant Reproduction introduction THE REMARKABLE EVOLUTIONARY SUCCESS of flowering plants can be linked to their novel reproductive strategies. In this chapter, we explore the reproductive strategies of the angiosperms and how their unique features —flowers and fruits—have contributed to their success. This is, in part, a story of coevolution between plants and animals that ensures greater genetic diversity by dispersing plant gametes widely. In a stable environment, however, there are advantages to maintaining the status quo genetically; asexual reproduction, for example, is a strategy that produces cloned individuals. An unusual twist to sexual reproduction in some flowering plants is that senescence and death of the parent plant follow.
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42.4 Pollination and Fertilization Early seed plants were wind-pollinated Flowers and animal pollinators have coevolved Some owering plants continue to use wind pollination Self-pollination is favored in stable environments Several evolutionary strategies promote outcrossing Angiosperms undergo double fertilization concept outline 42.1 Reproductive Development The transition to owering competence is termed phase change Mutations have clari ed how phase change is controlled f 42.2 Flower Production The light-dependent pathway is geared to the photoperiod The temperature-dependent pathway is linked to cold The gibberellin-dependent pathway requires an increased hormone level The autonomous pathway is independent of environmental cues Floral meristem identity genes activate oral organ identity genes 42.3 Structure and Evolution of Flowers Flowers evolved in the angiosperms Gametes are produced in the gametophytes of owers 42.5 Asexual Reproduction Apomixis involves development of diploid embryos In vegetative reproduction, new plants arise from nonreproductive tissues Plants can be cloned from isolated cells in the laboratory 42.6 Plant Life Spans Perennial plants live for many years Annual plants grow, reproduce, and die in a single year Biennial plants follow a two-year life cycle
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827 rav65819_ch42_827-850.indd 827 rav65819_ch42_827-850.indd 827 12/8/06 9:13:59 AM 12/8/06 9:13:59 AM 42.1 Reproductive Development In chapter 30, we noted that angiosperms represent an evolutionary innovation with their production of flowers and fruits. In chapter 36, we outlined the development of form, or morphogenesis, that a germinating seed undergoes to become a vegetative plant. In this section, we describe the additional changes that occur in a vegetative plant to produce the elaborate structures associated with flowering (figure 42.1). Plants go through developmental changes leading to reproductive maturity just as
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rav65819_ch42_827-850 - ; 42 chapter Plant Reproduction...

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