Lyons and Raison devised methods of isolating mitochondria from these plants so that they could compare the rates of respiration of the different mitochondria at chilling temperatures. He believed that sensitivity to chilling was related in some way to an activity associated with the mitochondria. Lyons had come to Australia to study the difference between chilling-resistant and chilling-sensitive plants. In 1968, Dr John Raison of the CSIRO Division of Food Research, who by then was devoting most of his research to mitochondria, was joined in Sydney by Dr James Lyons, Head of the Department of Vegetable Crops at the University of California, Riverside. Studies with plant mitochondria ‘ a eureka moment Enzymes associated with the membranes of the mitochondria help break down sugars into carbon dioxide and water and in doing so release considerable amounts of chemical energy ‘ a process known as cell respiration. This discovery stems from research on mitochondria ‘ minute particles embedded in the jelly-like cytoplasm that fills each cell. The key to the mechanism that enables some plants and animals to resist cold has been found in the myriad cells of which they are composed-more particularly, in the physical properties of the cell membranes. Why do cabbages and broad beans flourish in temperatures far below those which kill melons and tomatoes? How do reptiles, amphibia and fish survive temperatures lethal to many warmblooded animals? Why are some warm-blooded animals able to hibernate, and others not? How do some living organisms resist the cold better than others?įor many years scientists around the world were puzzled by the ability of certain plants and animals to tolerate low temperatures without distress, while others suffered injury and even death when exposed to the same temperatures. The practical applications of this work range from better plant production to preservation of organs for human transplantation. They went on to show that this was due to differences in the lipid composition of the mitochondrial membranes and that similar phenomena occurred in hibernating animals. The respiration rate of the mitochondria from cold-resistant organisms was more sustainable at lower temperatures than the respiration rate of the mitochondria from cold-susceptible organisms. In a eureka moment they discovered that the secret lay in the properties of the mitochondria, the small energy producing organelles in all cells. Why do some plants and animals tolerate cold stress while others succumb? The answer to this question has applications from food production to human medicine and it was discovered in the late 1960s by CSIRO’s John Raison and an American colleague James Lyons.
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