Exogenous ethylene increases methane emissions from canola by adversely affecting plant growth and physiological processes

It is well known that ethylene affects plants; however, its regulatory role in plant-derived methane (CH₄) has not been addressed. In this study, we determined the effects of exogenous ethylene on canola (Brassica napus L.) growth and physiological traits, endogenous ethylene, and aerobic methane emission. Plants were grown under experimental conditions (22/18 °C, 16 h light: 8 dark; 500 lmol photons·m^{2·s 1}) for 21 d and were exposed to exogenous ethylene for different durations (0, 1, or 2 h·d¹). Methane and ethylene emissions were measured after 7, 14, and 21 d, whereas growth and physiological traits were measured after 21 d. Overall, methane emissions decreased, but endogenous ethylene increased over time with exogenous ethylene. Plants treated with exogenous ethylene had decreased growth, biomass, gas exchange, chlorophyll fluorescence, photosynthetic pigments, and nitrogen balance index, but increased flavonoids. Both methane and ethylene were negatively correlated with most growth and physiological traits. In conclusion, this study revealed that exogenous ethylene significantly increased both endogenous ethylene and methane emissions. Plants exposed to exogenous ethylene were likely stressed and emitted methane, which increased with exposure time.