The Effects of Low Growth and Measurement Temperature on the Respiratory Properties of Five Temperate Species

Five temperate ruderal species, Epilobium glandulosum, Matricaria matricariodes, Melilotus alba, Sonchus asper and Taraxacum officinale, were grown under controlled conditions at both 10 °C and 20 °C. Respiration was measured at 10 °C and 20 °C. Total dark respiration rates of plants grown at 10 °C were consistently higher than the rates of plants grown at 20 °C. This was due to greater respiratory activity along both the cytochrome (KCN-sensitive) and alternative (SHAM-sensitive) pathways in the cold grown plants. The capacity to use the alternative pathway was also greater in the 10 °C grown plants. The increase in the relative contribution of each pathway was species specific. At a given growth temperature the activity of the alternative pathway varied little between measurements at 10 °C and 20 °C. In contrast, the activity of the cytochrome pathway was greater when measured at 20 °C than when it was measured at 10 °C. The capacity of the alternative pathway was lower when measured at 10 °C. These results suggest that the cytochrome pathway is more sensitive to temperature stress than is the alternative pathway.