The Oxidative Properties of Mitochondria and Bacteroids from Root Nodules of Soybean Treated with Organic Acids

Nodule mitochondria are highly sensitive to the respiratory inhibitor antimycine A. The antimycine-resistant oxygen uptake is 5–10% of the rate of control mitochondrial respiration. The high sensitivity to this inhibitor means that non-phosphorilating pathways are absent from the nodules and the energetic effectiveness of mitochondria is very high. The latter is proved by the good respiratory control, observed in mitochondria from soybean plant nodules. Mitochondria, isolated from nodules of plants that are treated with succinate and α-ketoglutarate during inoculation showed highest respiratory control. A significant differences in the rate of oxygen uptake by mitochondria isolated from soybean plant nodules were observed in all treatments investigated. The rates of oxygen consumption by mitochondria isolated from nodules of citrate treated plants were close to these of the control plants. However, treatment with succinate, malate and α-ketoglutarate resulted in a significant increase of mitochondrial oxygen uptake. Our results support the relation between plant photosynthesis and bacteroid respiration. Photosynthetic intensity and the oxygen uptake of bacteroids were the lowest in control soybean plants and the ones treated with citrate during inoculation. In the cases when the intensity of photosynthesis was high (treatments with succinate, malate and α-ketoglutarate during inoculation), the rate of oxygen uptake of the bacteroids was the highest. Results obtained indicate that the oxidative capacity of mitochondria and bacteroids from root nodules of soybean treated with organic acids succinate and