OXYGEN-CONSUMPTION STIMULATED BY DELTA-AMINOLEVULINIC-ACID IN DARKNESS AND DURING IRRADIATION OF DARK-GROWN WHEAT LEAVES

Dark grown wheat leaves (T. aestivum L. cv. Starke II Weibull), treated with .delta.-aminolevulinic acid in darkness, showed an increased O2 uptake as measured by a Warburg method. The production of CO2 was also increased in darkness, giving an RQ .apprxeq. 1. The increased respiration was dependent on the treatment time as well as on the concentration of the .delta.-aminolevulinic acid. Potassium cyanide suppressed both the normal and the increased respiration. The treatment with .delta.-aminolevulinic acid caused accumulation of high amounts of protochlorophyllide [PChlide]. Levulinic acid suppressed the increased O2 uptake as well as the PChlide accumulation in .delta.-aminolevulinic acid-treated leaves. Irradiation rapidly decreased the PChlide content with a simultaneous increase in O2 uptake over the dark value. The peak value of the increase in O2 uptake was reached after about 5 min. The light-induced O2 uptake was dependent on the amount of PChlide present at the onset of irradiation. The CO2 production was also increased during the first minutes of irradiation but soon fell under the buffer control value. Neither potassium cyanide nor heat denaturation affected the O2 uptake in light in contrast to the effect on the CO2 production, which was blocked by heat denaturation. The increased O2 uptake in light initially seems to be a purely photochemical process leading to a release of CO2, which release is probably an enzymatic process induced by the photo-oxidative decomposition of pigment.