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PLANT REPRODUCTION CHAPTER 41 This chapter is a continuation of Chapter 29. Study Fig. 41.13 again and know the differences between “complete” and “incomplete” flowers. Flowers have evolved for plant reproduction purposes and many plants depend heavily on animals for this purpose. Mutations in either the plant or animal pollinator can result in the lack of fertilization. Likewise, if flowering occurs out of sync with the pollinator’s life cycle, both species can suffer. Floral morphology has coevolved with animals. Floral organs are believed to have evolved from leaves. The trend is toward four distinct whorls: calyx, corolla , androecium , and gynoecium (Fig. 41.12). A “complete” flower has all these parts, whereas an “incomplete” flower lacks one or more of these four whorls. The calyx , the outer part, is made up of sepals which protect the flower when it is in bud (Fig. 41.13). The petals collectively make up the corolla and are often colored and arranged to attract the specific animal species, i.e., they may mimic the female of the animal species. Orchids are a good example of this mimicry (Fig. 41.15). Androecium is another term for “ stamens .” Stamens produce the microsporangia which produce the male gametophytes (Fig. 41.13). Stamen collectively includes the filaments and anther. Pollen begins in two pollen sacs in the anther. Each pollen sac contains microspore mother cells (Fig. 41.7). Microspore mother cells undergo meiosis to produce four haploid microspores, which divide by mitosis to produce specialized structures = pollen (Fig. 41.17). Each pollen grain contains a “tube cell nucleus” and a “generative cell” that will divide to produce two sperm cells. Each pollen grain has a morphology unique to that plant species – like a fingerprint. The Gynoecium is the collective term for all the female flower parts. The Gynoecium consists of the stigma , style , and ovary (Fig. 41.13). Pollen lands on the stigma, the “tube cell nucleus” forms a pollen tube, which provides a tube to the egg for purposes of pollination. The “generative cell” now divides by mitosis to produce two sperm nuclei. One sperm cell pollinates the “egg.” (Fig. 41.17).
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This note was uploaded on 03/31/2008 for the course BIOL 1106 taught by Professor Georgesimmons during the Spring '08 term at Virginia Tech.

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