Rapid plant rehydration initiates permanent and adverse changes in the photosynthetic apparatus of triticale

Abstract

Background and aims: The reasons for partial recovery after a soil drought are not fully understood and have not been studied so far. This study investigated the physiological and biochemical responses of triticale cultivars with differential recovery ability after soil water deficit. Methods: Activity of the photosynthetic apparatus under soil drought followed by rehydration was estimated. Plant antioxidant potential was determined based on the measurement of catalase and peroxidase activity. The levels of hydrogen peroxide and superoxide radical were assessed. Results: Under rehydration, the not fully-recovered cultivar experienced further significant increase in the content of H2O2 and inhibited activity of the photosynthetic apparatus, as compared to the drought period. On 42nd day of the rehydration, the not fully-recovered cultivar showed also a reduced photosynthetic activity in the flag leaves, which resulted in a significant decrease in its grain yield. The first week of a rapid rehydration involved a decrease in total peroxidase and catalase activities. The increased content of H2O2 was compensated only when leaf water content was gradually restored in the first week of the rehydration and no further decrease in the activity of the photosynthetic apparatus was noticed. Conclusions: A destructive effect of the rapid rehydration was manifested in an intensification of the physiological processes associated with reactive oxygen species (ROS) overproduction. An important cause of hydrogen peroxide overproduction seems to be the electron leakage due to overloading of the electron transport chain (ETC) in the PSI and PSII.