Author
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Harper, James |
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Submitted to: Plant Microbe Interactions and Biological Control
Publication Type: Abstract Only Publication Acceptance Date: 10/28/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The interaction of carbon and nitrogen metabolism is one of several proposed mechanisms of nodulation control (inhibition) when legumes are provided nitrate nutrition. The hypothesis tested was that the extent of inhibition of nodulation by nitrate was related to N status of the plant at the time nitrate treatment was imposed. For both genotypes, N concentration in shoots was significantly negatively correlated to N2ase activity and positively correlated to the extent of N2ase inhibition by NO3-. Furthermore, N2ase activity was significantly positively correlated to total nonstructural carbohydrates in nodules and C:N ratio in shoot and nodules for both genotypes. Nitrogenase inhibition by NO3- was significantly negatively correlated to TNC and C:N ratio in shoots, but not in nodules for both genotypes. At the onset of N2ase inhibition by NO3-, TNC declined in shoots but increased in roots and nodules. N levels increased in shoots and roots but not in nodules following NO3- treatment. It is suggested that the level of N2ase activity and sensitivity to inhibition by NO3- may be determined by 1) plant N needs (as determined by shoot C:N ratio) and 2) availability of carbohydrates in nodules. Modulation of N2ase activity may occur through sensing changes in plant N, i.e., changes in shoot C:N ratio, possibly through some phloem translocatable compound(s). It has been observed that asparagine concentration increases dramatically in shoots of plants exposed to short-term NO3- treatment. This has led to speculation that asparagine may be a phloem translocatable compound involved in feedback control of nodulation and nodule activity in response to NO3- treatment. |
