<p> The experiments described in this thesis were performed to study the:
1. Role of nitrate in the induction of nitrate reductase.
2. Effect of nitrate on the in vivo regulation of nitrate reductase.
3. Role of atrazine on the regulation of nitrate reductase.</p> <p> The nitrate reductase assay system was improved up to 10 fold over that previously used (28). This improvement included the addition of oxalacetic acid and malic dehydrogenase to the system, thereby oxidizing all the NADH at the end of the reaction. NADH, which was a required co-factor in the assay system, interfered with the nitrite colour formation.</p> <p> When the induction kinetics of the enzyme are followed in root tip sections (0 -10 mm) of corn, a 25 minute lag period followed by a period of rapid nitrate reductase synthesis is seen. Neither the lag period nor the rate of increase in enzyme activity is affected by the concentration of the inducer used (1.0, 10.0 or 25.0 mM nitrate), However, with concentrations of nitrate from 0.1 mM to 10.0 mM, there is an increase in the final level of nitrate reductase. Nitrate levels between 10.0 mM to 100.0 mM did not alter this maximally induced level of enzyme.</p> <p> In mature root sections (25-35 mm from the tip), a longer lag time and a slower rate of increase in enzyme activity is seen. The system is not saturated with nitrate concentrations up to 100.0 mM.</p> <p> Cycloheximide, a protein synthesis inhibitor, was added to the roots after the enzyme had been maximally induced. This allowed one to study the in vivo turnover of the enzyme. Nitrate did not alter the in vivo turnover of nitrate reductase in corn roots.</p> <p> Atrazine is a herbicide that has been reported to increase nitrate reductase levels in corn (34). When used in the experiments described here, it was found to be ineffective in altering the nitrate reductase activity of the roots and leaves of corn.</p> / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/20309 |
| Date | 09 1900 |
| Creators | Stevens, Donald Larry |
| Contributors | Oaks, Ann, Biology |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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