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Wheat mitochondria: oxidative activity and membrane lipid structure as a function of temperature
J K Raison1, E A Chapman, P Y White
1Plant Physiology Unit, CSIRO Division of Food Research and School of Biological Sciences, Macquarie University, North Ryde, N.S.W. 2113, Australia.
Plant Physiology
|April 1, 1977
Summary
Wheat
Area of Science:
- Plant Physiology
- Biochemistry
- Molecular Biology
Background:
- Mitochondrial function and membrane lipid structure are crucial for plant adaptation to temperature.
- Wheat (Triticum aestivum L.) is a globally important crop, and understanding its chilling resistance mechanisms is vital.
Purpose of the Study:
- To investigate the impact of temperature on mitochondrial oxidative activity and membrane lipid phase transitions in wheat cultivars.
- To determine the activation energy of key mitochondrial respiratory enzymes and analyze factors affecting it.
- To characterize the phase transition behavior of wheat membrane lipids in relation to chilling resistance.
Main Methods:
- Measurement of mitochondrial oxidative activity (succinate and alpha-ketoglutarate oxidation, succinate-cytochrome c oxidoreductase activity) at varying temperatures.
- Analysis of Arrhenius activation energy for enzymatic reactions.
- Application of three spin-labeling techniques to study membrane lipid structure and phase transitions.
- Investigation of factors influencing mitochondrial respiration rates, including mitochondrial concentration, respiration inhibition, and isolation time.
Main Results:
- Arrhenius activation energy for succinate, alpha-ketoglutarate oxidation, and succinate-cytochrome c oxidoreductase activity remained constant between 3 and 27 C.
- Mitochondrial concentration, initial state 3 respiration inhibition, and isolation time affected low-temperature oxidation rates, causing apparent increases in activation energy.
- Wheat membrane lipids exhibited phase changes around 0 C and 30 C, as detected by spin-labeling.
- These phase transitions in wheat, a chilling-resistant plant, initiate at lower temperatures and span a wider range compared to chilling-sensitive plants.
Conclusions:
- Mitochondrial oxidative activity in wheat shows consistent activation energy within a specific temperature range, but experimental conditions can alter this.
- Wheat membrane lipids undergo temperature-induced phase transitions, contributing to the plant's chilling resistance.
- The observed phase transition characteristics in wheat suggest an adaptation mechanism for surviving low temperatures.
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