Physiological and biochemical changes associated with the induction of facultative CAM in Pereskia aculeata under drought stress and recovery

Climate change-induced drought increasingly threatens plant productivity. Facultative Crassulacean Acid Metabolism (CAM) represents a potential adaptive strategy, allowing plants to optimize water use efficiency, but the mechanisms underlying its induction and regulation remain poorly understood in many edible wild plant species. This motivated the present study which aimed to characterize the physiological and biochemical changes associated with the induction of facultative CAM in Pereskia aculeata under drought stress and subsequent recovery. Seedlings were subjected to a 60-day drought period followed by rehydration. We assessed the effects on growth, water status, gas exchange, chlorophyll fluorescence, CAM-related physiological parameters (titratable acidity, malate content, and the activities of phosphoenolpyruvate carboxylase (PEPc) and malate dehydrogenase (MDH)), as well as reactive oxygen species (ROS) metabolism. Drought induced significant nocturnal accumulation of malate and nocturnal acidity and increased the activities of PEPc and MDH. While antioxidant enzyme activities decreased during drought, they increased significantly after rehydration. Collectively the data suggest an induction of facultative CAM in P. aculeata under drought and highlight key physiological and biochemical changes accompanying this C3 to CAM photosynthesis transition that may assist in balancing productivity and water conservation and managing oxidative stress during drought. This study provides valuable insights into the physiological and biochemical mechanisms underlying CAM induction in wild species, which points to their potential for enhancing drought tolerance in plants, particularly in the context of climate change.