biologylabreport - Effects of gibberellic acid on the...

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Effects of gibberellic acid on the rosette and wild-type phenotypes of Brassica rapa
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Introduction Plant hormones are signaling molecules that are produced in one tissue of an organism and then transported to another tissue to generate a response in cells and tissues. The multiple plant hormones are present in almost all parts of plant growth and development, working either alone or in conjunction with another hormone. Auxin (indoleacetic acid) promotes stem elongation, root formation, fruit development, and brings out apical dominance. Cytokinins stimulate cell division and germination. Gibberellins stimulate stem elongation, seed germination, and fruit growth. Brassinosterioids promote cell elongation division, seed germination, and xylem differentiation while inhibiting phloem differentiation. Abcisic acid is a plant inhibitor, slowing growth, maintaining dormancy, and closing the stomata during stress. Another hormone like abcisic acid is ethylene, which promotes fruit ripening and the triple response, which involves a slowing of stem elongation, thickening of the stem, and growing of horizontal stems (Campbell and Reece, 2008). An example of plant hormones working in conjunction with another can be seen in plants with different ratios of cytokinins to auxins present. In plant cells with only cytokinins present, only cell growth will occur, but as auxins are added, both cell growth and division occur. Auxin and cytokinins also collaborate in controlling auxiliary bud inhibition. More illustrations of plant hormones cooperating include the partnerships gibberellins make; both gibberellins and auxin must be present in order for fruit to develop, and the ratio of abcisic acid to gibberellins determines whether a seed will remain dormant or germinate (Campbell and Reece, 2008). Gibberellins, the main focus of this research, are found on the meristems of apical buds and roots and young leaves (Campbell and Reece, 2008).There are multiple types of gibberellins,
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with each type behaving differently in systems. Gibberellic acid is considered GA 3 . When gibberellic acid is applied to plants at low concentrations, obvious growth should be noticeable, while higher applications of gibberellic acid might stunt plants growth (Riley, 1987). While gibberellins stimulate stem elongation, they have little effect on roots. Plants without normal amounts of gibberellins have stunted growth. Past experiments including the addition of stem-
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This note was uploaded on 08/07/2009 for the course BY 124 taught by Professor Cusic during the Spring '08 term at University of Alabama at Birmingham.

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biologylabreport - Effects of gibberellic acid on the...

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