EFFECTS OF TEMPERATURE ON INFECTED CELL O-2 CONCENTRATION AND ADENYLATE LEVELS IN ATTACHED SOYBEAN NODULES

To assess the role of O-2 in the regulation of nodule metabolism follo wing a decrease or an increase in temperature, the fractional oxygenat ion of leghemoglobin (FOL) was measured in soybean (Glycine max L. Mer r.) nodules during rapid and gradual changes in temperature from 20 de grees C to either 15 or 25 degrees C. The affinity of leghemoglobin fo r O-2 was also measured at each temperature and the values were used t o calculate the infected cell O-2 concentration (Oi). After nodules we re transferred to 15 degrees C, FOL and Oi increased and adenylate ene rgy charge (AEC = [ATP + 0.5ADP]/[ATP + ADP + AMP]) increased from 0.7 0 to 0.78. The temperature increase was associated with a decrease in FOL and Oi. We concluded that changes in nodule temperature alter the respiratory demand of the nodules for O-2, resulting in a change in Oi and a shift in the balance between ATP consumption and ATP production within the nodule tissue.