angiodevelop213-page8

angiodevelop213-page8 - Bean Germination Corn Germination...

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Flowering Plants: Early Growth and Development - 8 Process of Germination 1. Emergence of the radicle, which is positively gravitropic 2. Emergence of the hypocotyl (or epicotyl), which is usually arched (from the bent embryo position). The bent hypocotyl protects the shoot axis meristem. 3. Upward (or negatively gravitropic) growth of the hypocotyl and shoot axis, which must be rapid. If nutrient reserve is consumed before the emergence above ground, the plant will die. 4. The exposure of the shoot to light triggers the development of chlorophyll and also straightens out the shoot. Rapid establishment of roots for water and mineral absorption and chlorophyll development in the shoot are critical, so that the seedling can provide its own nutrient supply via photosynthesis. If everything is successful, a new plant is established which will continue to exhibit an open growth pattern.
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Unformatted text preview: Bean Germination Corn Germination Before we leave this subject, it is beneficial to mention two exceptions to normal seed development. (Methods of asexual propagation will be discussed with our plant modified structures section.) Apomyxis Seeds are produced without fertilization Example: Dandelion seeds Parthenocarpy Many fruits can be produced without seed development. This process, called parthenocarpy, may or may not require pollination. Certain hormones regulate the maturation of the ovary into the fruit portion of the plant. Either mutation, such as with the navel orange, or the use of hormone sprays on flowers, can result in the maturation of the ovary without seeds. Parthenocarpic plants must be propagated asexually. Navel oranges, for example, are propagated by grafting branches that produce navel oranges onto other orange tree stock....
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