The involvement of ethylene in the response of maize seedlings to mechanical impedance /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Crop establishment is often hindered by tillage pans and high bulk densities in the soil profile. Crusting at the soil surface may prevent shoot emergence, resulting in irregular stands. Plant responses to these conditions are presumed to be under hormonal regulation. Prior work has implicated the hormone ethylene as a potential regulator. The objectives of this research were to relate the growth response of mechanically impeded seedlings to the production of ethylene and the metabolism of its precursor, 1- aminocyclopropane-1-carboxylic acid (ACC). A triaxial cell system was used to simulate mechanical impedance by compressing the growth medium around the growing tissue in a controlled environment. The system allowed continuous and precise measurement of ethylene production by intact seedlings as they experienced the stress. Elongation of maize primary roots and shoots was severely hindered by applied pressures as low as 10 kPa. Shoots were more affected than roots at higher pressures. Radial expansion was promoted in both organs by mechanical impedance. Morphological changes were not evident until 3 h after treatment initiation. Ethylene production rate increased up to 255% 1 h after treatment initiation, and continued to increase linearly for at least 10 h. Tight coupling between mechanical impedance and ethylene production was evidenced by cyclic application and relaxation of the stress treatment. Exposure to exogenous ethylene caused symptoms similar to those shown by plants grown under mechanical impedance, and inhibitors of ethylene synthesis or action maintained ethylene production rates of impeded seedlings at basal levels with concomitant partial restoration of tissue elongation. In vivo ACC synthase activity increased 6-fold at 25 kPa 1 h after treatment initiation. However, immediate conjugation of ACC prevented excessive accumulation of free ACC. In vivo ethylene forming enzyme (EFE) activity was significantly greater at 100 kPa than in controls as early as 1 h after treatment initiation. The evidence indicates that ethylene plays a pivotal role in the regulation of plant tissue response to mechanical impedance, and that regulation of ethylene synthesis under mechanical impedance involves the concerted action of ACC synthase, EFE, and ACC-N-malonyl transferase. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Plant Physiology." |
| Physical Description: | xiv, 98 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |