ISHS Acta Horticulturae 618: XXVI International Horticultural Congress: Environmental Stress and Horticulture Crops
THE RELATIONSHIP BETWEEN COQ10 CONTENT AND RESPIRATION RATE OF FIVE ETIOLATED SEEDLING SPECIES |
| Authors: | K.D. Munro, D.M. Hodges, J.M. DeLong, C.F. Forney |
| Keywords: | ubiquinone, ubiquinol, antioxidant, mitochondria |
| Abstract:
Ubiquinone, or Coenzyme Q10 (CoQ10), functions primarily in the electron transport chain of the mitochondria of plants and animals. The molecule contains a benzo-quinone head group and a long isoprenoid tail that anchors the molecule in the membrane. Secondary roles in plant tissue, such as antioxidant activity, have also been proposed for ubiquinone. This study examines a potential relationship between respiration rate and ubiquinone content during the development of five species of etiolated seedlings. Respiration rate may be an approximate indicator of the ubiquinone content of different types of plant tissue. Seedlings were grown in dark environmental cabinets (20°C) and the beginning of the experiment was the day on which seedlings reached 50% germination, as established in a previous study (data not shown). Ubiquinone content differed between species and levels within each species varied significantly over the course of the experiment. The reduction of the ubiquinone pool was high, indicating a large degree of saturation of the respiration pathways in these seedlings. In general, respiration rates declined as the seedlings aged. Ubiquinol (Qr), the reduced form of the molecule, and total ubiquinone (Qt), correlated with CO2 evolution but not with O2 consumption. Ubiquinone (Q), the oxidized form of the molecule, did not correlate with either CO2 evolved or O2 consumption. However, the ratio of ubiquinol to total ubiquinone, known as the redox status (Qr/Qt) of ubiquinone, showed a positive correlation with both CO2 evolved and O2 consumption. The relationship between respiration rate and CoQ10 may be less dependent on the overall concentration of CoQ10 and influenced more by the redox status of the Q-pool in plant mitochondrial membranes. | |
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