Plants10 - root growth and differentiation and produce an enzyme that pro motes the conversion of an embryo's starchy food supply into utilizable

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Plants: Essential Processes Cytokinins The cytokinin hormones promote cell division and tissue growth, and depend upon the presence of auxins to determine the extent of their activity. When the ratio of cytokinins to auxins is relatively high, stem and leaf growth is stimulated. When, on the other hand, the ratio of cytokinins to auxins is relatively low, root growth is stimulated instead. The balance between these hormones ensures that the plant invests in both root and shoot growth, so that neither becomes too large or small for the other. Cytokinins are also involved in the development of chloroplasts, fruits, and flowers. In addition, they have been show n to delay senescence (aging), especially in leaves, which is one reason that florists use cytokinins on freshly cut flowers. Gibberellins Gibberellins stimulate growth, especially elongation of the stem, and can also end the dormancy period of seeds and buds by encouraging germination. Additionally, gibberellins play a role in
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Unformatted text preview: root growth and differentiation, and produce an enzyme that pro motes the conversion of an embryo's starchy food supply into utilizable sugars. In some plants, these hormones are essential for flowering and fruit development. Inhibitors True to their name, inhibitors restrain growth and maintain the period of dormancy in seeds and buds. The most important of this type of hormone is abscisic acid, which in addition to restraining growth, causes the guard cells, of the stomata to close when the plant is losing too much water. Ethylene Ethylene is best known for controlling the ripening of fruits. It also contributes to the senescence (aging) of plants by promoting leaf loss (termed leaf abscission) and other changes. Ethylene can bring buds and seeds out of dormancy, initiate flo wer development, and promote radial (horizontal) growth in roots and stems. Interestingly, in certain circumstances ethylene can also act as a growth inhibitor, most often in conjunction with auxin....
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This note was uploaded on 01/27/2012 for the course BIOLOGY BSC1005 taught by Professor Rodriguez during the Winter '09 term at Broward College.

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