Abstract
The time course of respiration in soybean plants was examined under different physiological conditions to elucidate the mechanism of the determination of respiration rate. Respiratory CO2 evolution per unit dry weight (RPW) decreased after the onset of the dark period and showed a temporary acceleration around midnight, called the midnight rise of respiration (MRR) in this paper, reaching a constant level at about 48 hours after the initiation of the dark. Throughout this time course, RPW was high in younger and nitrogen-supplied plants, and low in the aged or nitrogen-depleted plants. Furthermore, MRR disappeared in the aged or nitrogen-depleted plants. From the results obtained, it was hypothesized that the time course of RPW, especially the existence of MRR, was determined by the demand for the energy and metabolic products which could be derived from respiration.
