Carbon Metabolism in Relation to Cellular Organization of Soybean Root Nodules and Respiration of Mitochondria Aided by Leghemoglobin

Abstract

Effects of leghemoglobin on the respiration of bacteroids and mitochondria were examined by following oxygen uptake. Oxyleghemoglobin prepared from soybean nodules promoted the uptake of oxygen by bacteroids isolated aerobically from soybean nodules. Uptake of oxygen by both the nodule mitochondria and the hypocotyl mitochondria was also stimulated by the oxyleghemoglobin. The stimulatory effect of leghemoglobin on the respiration of the nodule mitochondria became highly significant as the amount of mitochondria injected into assay vial increased. The infected cells, the uninfected cells and the cortex tissue were isolated by enzymatic maceration from soybean nodules, and some enzyme activities were measured in these three fractions. Activities of alcohol dehydrogenase, pyruvate decarboxylase and phosphoenolpyruvate carboxylase in the infected cells were lower than in the uninfected cells and in the cortex tissue. Uricase activity was low in the cortex tissue and was highest in the uninfected cells. These results suggested that ethanol production is more active in the uninfected cells and the cortical cells than in the infected cells, and that respiration of the mitochondria in the infected cells of soybean nodules is more active, aided by the leghemoglobin.