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Effect of temperature on nitrogenase functioning in cowpea nodules
R M Rainbird1, C A Atkins, J S Pate
1Botany Department, University of Western Australia, Nedlands Western Australia 6009 Australia.
Plant Physiology
|October 1, 1983
Summary
Diurnal temperature variations significantly alter nitrogenase activity in cowpea symbioses, affecting the ratio of nitrogen fixed to hydrogen evolved. Constant temperatures stabilize this ratio, highlighting temperature
Area of Science:
- Plant-microbe interactions
- Biochemistry
- Environmental science
Background:
- Nitrogenase (EC 1.7.99.2) is crucial for biological nitrogen fixation in legume symbioses.
- Cowpea (Vigna unguiculata) symbiosis with Rhizobium exhibits complex physiological responses.
- Uptake hydrogenase-deficient Rhizobium strains impact the efficiency of nitrogen fixation.
Purpose of the Study:
- To investigate the diurnal variation in nitrogenase activity under fluctuating temperature conditions.
- To determine the effect of constant versus variable temperatures on nitrogen fixation and hydrogen evolution.
- To elucidate the influence of root temperature on electron allocation by nitrogenase.
Main Methods:
- Cultivation of cowpea (Vigna unguiculata cv Caloona) with Rhizobium strain (176A27) lacking uptake hydrogenase.
- Controlled environment experiments with diurnal (12h day/12h night) and constant temperature regimes.
- Measurement of nitrogen fixed and hydrogen evolved by nitrogenase activity.
- Exposure to a range of root temperatures (15-47°C) to assess enzyme function.
Main Results:
- Diurnal temperature fluctuations (30°C day/20°C night) caused significant variation in the ratio of nitrogen fixed to hydrogen evolved.
- Constant temperature (30°C) abolished diurnal variation, maintaining a stable ratio.
- Hydrogen evolution increased with temperature up to 35°C, while nitrogen fixation was less affected until above 38°C.
- A linear relationship was observed between temperature and the proportion of electrons allocated to proton reduction versus nitrogen reduction.
Conclusions:
- Temperature, particularly diurnal fluctuations, plays a critical role in regulating nitrogenase efficiency in cowpea symbioses.
- Optimizing temperature regimes can enhance biological nitrogen fixation by influencing electron partitioning in nitrogenase.
- Understanding these temperature effects is vital for improving crop yields and nitrogen use efficiency in agriculture.
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