Effects of low temperature on root respiration of Cynodon dactylon and its relationship with cold resistance

Root respiration in bermudagrass (Cynodon dactylon) is the only source of energy and is crucial for normal growth and winter survival. In this study, ‘Xinnong No. 1’ and Tifdwarf Bermudagrass with different levels of cold resistance were selected and the effect of low-temperature on root respiration of bermudagrass and its relationship with cold resistance was examined at 25 ℃ (control) and 4 ℃. The results showed that low-temperature stress notably decreased the root activity of bermudagrass and increased the relative conductivity and H₂O₂ content. Compared with ‘Xinnong No. 1’, the effect of low-temperature on Tifdwarf Bermudagrass was significantly more severe (P < 0.05). The low-temperature exposure reduced the total respiration rate and the cytochrome oxidase and alternative oxidase (AOX) respiration rates in the roots of bermudagrass; however, the decrease in ‘Xinnong No. 1’ was more significant (P < 0.05). Furthermore, the ratio of AOX respiration to total respiration in the roots of ‘Xinnong No. 1’ increased significantly (P < 0.05). Under low-temperature, the inhibition of AOX respiration significantly decreased the root activity, increased relative conductivity, and accumulation of H₂O₂ (P < 0.05) compared with those subjected to 25 ℃, but did not significantly differ from those of Tifdwarf Bermudagrass. These results indicate that AOX reduced reactive oxygen species accumulation, reduced oxidative damage to the cell membrane, and maintained a high root activity under low-temperature, thus playing an important role in protecting the root system. The relative activity of AOX respiration in the roots of bermudagrass was significantly increased (P < 0.05) in ‘Xinnong No. 1’, which increased its resistance to low-temperature.