Temperature tolerance threshold and mechanism of oxidative damage in the leaf of Coffea arabica 'Typica' under heat stress

Coffea arabica, an economically important crop, accounts for most of the coffee consumed globally. Increasing temperature due to climate change can cause a decrease in productivity in many crops, including coffee plants. The maximum temperature at which damage is induced has been reported for many crops, but it remains unclear in coffee plants. Here, we investigated the effect of different temperatures and the physiological damage induced by heat stress using both leaf disks and intact plants of Coffea arabica 'Typica'. In the experiment using intact plants, we observed leaf damage by a decrease in soil plant analysis development value, and an increase in electrolyte leakage after exposure to 45 degrees C for 96 h, whereas no leaf damage was observed for 72 h. The leaf surface temperatures after exposure to 45 degrees C for 72 and 96 h were 44.0 and 46.3 degrees C, respectively. Thus, a tolerance threshold in leaves of C. arabica 'Typica' under heat stress are likely between 44.0 and 46.3 degrees C. The activities of catalase (CAT) and superoxide dismutase (SOD) decreased at 45 degrees C in both leaf disks and intact plants. The decrease in the activities of SOD and CAT under heat stress may be responsible for the increased levels of reactive oxygen species, such as O-2(-) and H2O2, and the resulting cellular damage. Our findings provide valuable insights into the physiological responses of Coffea arabica 'Typica' to heat stress, which may contribute to the breeding and screening of tolerant cultivars in the future.