ALTERATION OF THE RESPIRATORY-FUNCTION IN CHILL-SENSITIVE CALLUS DUE TO LOW-TEMPERATURE STRESS .1. INVOLVEMENT OF THE ALTERNATE PATHWAY

The diversion of electron flow to the alternate pathway in mitochondria of chillsensitive callus of Cornus stolonifera was studied with reference to the immediate response of the cells to chilling. Temperatures below 15°C diverted the bulk of respiration to the alternate path, proportionally as the temperature decreased to 0°C. The alternate path, however, existed in cells in a suppressed form at temperatures above 15°C. In chill-resistant callus of Sambucus Sieboldiana, no alteration was noted in electron apportionment between the cytochrome path and the alternate path. Thus, there seems to be a marked difference in the mode of respiration between sensitive and resistant plant cells at low temperatures. The respiratory control ratio also markedly declined at temperatures below 15°C in chill-sensitive callus, but a higher respiratory control ratio was observed below 10°C in chill-resistant callus. From these results, an alteration in the regulatory system for electron apportionment between the two paths is probably the most immediate response of chill-sensitive cells to low temperatures. © 1979 Oxford University Press.