Research Paper 2

Research Paper 2 - Effects of exogenously applied...

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Effects of exogenously applied giberellin on growth of wild type and rosette strain Brassica rapa Melissa Harintho Heather Eisler BIOS 10162 Section 3 April 22, 2008
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Abstract Chemical regulation is one of the most important biological systems affecting living organisms. In plants, chemical control is conducted by regulation of chemical signaling. The study organism Brassica rapa provides an ideal plant model system, because it has a short seed to seed life cycle, a strong correlation of structure with physiological function, and it allows for relatively easy application or topical hormone and care. In this experiment, different concentrations of gibberellin (ranging from 2.5-100 µg) were exogenously applied to wild type and rosette strain Brassica rapa (in replicates ranging from 157 to 201 for control groups and 13 to 40 for trial groups). The topically applied gibberellin produced significant differences (p < 0.0001, using ANOVA) between means within the data: there was a statistically significant increase (p < 0.05, using a Tukey’s MCT) in the mean heights of the dwarfs as compared to the untreated dwarf plants. Furthermore, the mean heights of the dwarf trial groups did not statistically differ (p > 0.05, using a Tukey’s MCT) from that of the wild type control group. The results suggest that the exogenously applied gibberellin fully restored the wild type phenotype in treated dwarf plants. Since the data suggest that increased gibberellin concentration caused the restoration of the wild type phenotype in the dwarf plants, we consequently concluded that the physiological receptors were functional in the dwarf plants. We did not, however, detect any quantitative differences in sensitivity of growth response. Such results were probably due to the utilization of dose concentrations not conducive to observing dose-dependent patterns in wild type stock and rosette strain Brassica rapa . Future studies using different concentrations of gibberellin would shed more light on quantitative differences in sensitivity of growth response in dwarf and wild type plants.
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Introduction Plants have a wide-ranging ability to adjust to external conditions. One hormone that contributes to the flexible response system of plants is gibberellin, a chemical messenger that promotes growth in many different types of plants. Gibberellin has a wide variety of roles ranging from seed germination and leaf expansion to flowering and stem elongation (Bonetta et al. 2005). Although over 125 gibberellins have been identified, only gibberellin A has specifically demonstrated control over stem elongation. Gibberellin A contributes to bolting, or rapid shoot elongation of apical meristems in reaction to environmental signals. In nature, plants produce more gibberellin in response to longer days or colder weather. Experimentally, the direct role of gibberellin on plant growth was illustrated in a study in which some plant species demonstrated bolting when sprayed with a gibberellin solution without exposure to any
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This note was uploaded on 05/18/2008 for the course BIOS 11161 taught by Professor Olsen during the Fall '08 term at Notre Dame.

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Research Paper 2 - Effects of exogenously applied...

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