Chapter 38 Angiosperm Reproduction and Biotechnology

Chapter 38 Angiosperm Reproduction and Biotechnology -...

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Chapter 38 Angiosperm Reproduction and Biotechnology Lecture Outline Overview: To Seed or Not to Seed Sexual reproduction is not the sole means by which flowering plants reproduce. Many species can also reproduce asexually, creating offspring that are genetically identical to them. The propagation of flowering plants by sexual and asexual reproduction forms the basis of agriculture. For 10,000 years, plant breeders have altered the traits of a few hundred angiosperm species by artificial selection, transforming them into today’s crops. Concept 38.1 Pollination enables gametes to come together within a flower Sporophyte and gametophyte generations alternate in the life cycles of plants. The life cycles of angiosperms and other plants are characterized by an alternation of generations, in which haploid (n) and diploid (2n) generations take turns producing each other. o The diploid plant, the sporophyte, produces haploid spores by meiosis. o These spores divide by mitosis, giving rise to multicellular male and female haploid plants—the gametophytes. o The gametophytes produce gametes—sperm and eggs. o Fertilization results in diploid zygotes, which divide by mitosis to form new sporophytes. In angiosperms, the sporophyte is the dominant generation, the conspicuous plant we see. o Over the course of seed plant evolution, gametophytes became reduced in size and dependent on their sporophyte parents. Angiosperm gametophytes are the most reduced of all plants, consisting of only a few cells. In angiosperms, the sporophyte produces a unique reproductive structure, the flower. o Male and female gametophytes develop within the anthers and ovules, respectively, of a sporophyte flower. o Pollination by wind, water, or animals brings a male gametophyte (pollen grain) to a female gametophyte contained in an ovule embedded in the ovary of a flower. Union of gametes (fertilization) takes place within the ovary. Ovules develop into seeds, while the ovary itself develops into the fruit around the seed. Flowers are specialized shoots bearing the reproductive organs of the angiosperm sporophyte. Flowers, the reproductive shoots of the angiosperm sporophyte, are typically composed of four whorls of highly modified leaves called floral organs, which are separated by very short internodes.
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o Unlike the indeterminate growth of vegetative shoots, flowers are determinate shoots in that they cease growing once the flower and fruit are formed. The four kinds of floral organs are the sepals, petals, stamens, and carpels. o Their site of attachment to the stem is the receptacle. Sepals and petals are sterile. o Sepals, which enclose and protect the floral bud before it opens, are usually green and more leaflike in appearance than the other floral organs. o
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Chapter 38 Angiosperm Reproduction and Biotechnology -...

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