Temperature-induced Phase Changes in the Membranes of Glyoxysomes, Mitochondria, and Proplastids from Germinating Castor Bean Endosperm

Sucrose-gradient purified mitochondria, glyoxysomes, and proplastids from germinating castor bean (Ricinus communis L.) endosperm were examined by electron-spin resonance spectroscopy. A temperature-induced phase change was demonstrated in all of these organelles, their derivative membranes, and in micelles formed from the membrane phospholipids. The apparent transition temperature of the membrane lipids varied slightly between the samples, but in all cases, fell within the temperature range around 10 C where physiological and biochemical changes in the response to temperature for most chilling-sensitive plants occur.