Abstract
The effect of temperature upon ion uptake and respiration was investigated with excised roots of corn (Zea mays) and barley (Hordeum vulgare). A strong inhibition (Q(10) = 5 to 8) of ion uptake was observed at temperatures below 10 C. At higher temperatures more normal temperature dependencies (Q(10) = 1.3 to 2) were obtained. When the data were plotted according to the Arrhenius relationship, two different activation energies were indicated above and below 10 C. Other studies have related such changes with temperature in activation energy of processes to changes in membrane properties induced by temperature. These results suggest that such phase transitions may affect ion uptake processes. If so, then differences among species in their capacity to maintain normal root function at low soil temperature and to resist low temperature stress may be related to differences in the physical properties of cellular membranes.