FIGURE 6.

Influence of ammonium (NH₄⁺) nutrition on S-D-lactoylglutathione (SLG) and D-lactate catabolism. Activity of (A) mitochondrial glyoxalase (GLX) II and (B) D-lactate dehydrogenase; (C) mitochondrial oxygen consumption with SLG or D-lactate as substrates; (D) D-lactate levels in leaf tissue; (E) cytochrome c protein levels in isolated and purified mitochondria and (F) activity of complex III of the electron transport chain in leaf tissue of nitrate (NO₃^–)-grown and NH₄⁺-grown plants. Proteins from the mitochondrial fraction were resolved by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electroblotted on a polyvinylidene difluoride membrane, probed with a polyclonal antibody against cyt c, and visualized by chemiluminescence. Signal intensity, corresponding to cyt c (molecular mass, approximately 14 kDa) versus mitochondrial porin VDAC1 which was used for protein level normalization, was estimated using Quantity One 4.6.2 after background correction. Results are expressed relative to the control; the amount of protein in mitochondria isolated from the leaf tissue of NO₃^–-grown plants was set at 1.00. Representative results are shown. Values are the mean ± standard deviation (SD) of 3–5 biological and 1–3 technical replicates. Significant differences (P ≤ 0.05) between NO₃^–-grown and NH₄⁺-grown plants are indicated by an asterisk (^∗).