The effect of temperature on glutathione S-transferase activity and glutathione content in Alopecurus myosuroides (black grass) biotypes susceptible and resistant to herbicides

Herbicide‐resistant populations of Alopecurus myosuroides (black grass) have become widespread throughout the UK since the early 1980s. Previous observations in this laboratory have demonstrated that natural climatic fluctuations caused increases in endogenous glutathione S‐transferase (GST) enzyme activity in A. myosuroides plants as they mature, which is thought to be linked to herbicide resistance in this species. The present study has investigated the effects of plant growth at 10°C and 25°C, and reports GST specific activity and glutathione (GSH) pool size in resistant and susceptible A. myosuroides biotypes. Findings demonstrate differences in GST activity between resistant and susceptible populations, which are transient at lower growth temperatures. The GSH pool size was elevated at lower growth temperature in both biotypes. We speculate that these endogenous responses are part of a natural mechanism of acclimation to environmental change in this species and suggest that resistant plants are more able to adapt to environmental stress, as indicated in this instance by temperature change. These observations imply that the control of resistant A. myosuroides by graminicides may be more effective when applied at lower temperatures and at earlier growth stages.