ROS Equilibrium in the Digestive Fluid of the Nepenthes × ventrata Trap at Various Developmental Stages

Carnivorous plants, such as Nepenthes (Nepenthaceae), possess a unique feature: the external digestion of animal-origin food. Nepenthes × ventrata pitchers are filled with digestive fluid containing: enzymes, small regulatory compounds and reactive oxygen species (ROS), which also act as signalling molecules. The aim of this study was to investigate the pattern of ROS content and to characterise enzymatic and non-enzymatic ROS modulators in the digestive fluid of N. × ventrata at various developmental stages of the pitcher. Significant changes were observed in the levels of hydrogen peroxide (H2O2) and hydroxyl radical (•OH) throughout trap development. The highest concentration of H2O2 was found in aged pitchers, while the highest level of •OH was recorded in freshly opened immature traps. These findings corresponded with superoxide dismutase and class III peroxidase activities. After maturation of the trap, there was an increase in the activity of diamine and polyamine oxidases. We suggest that the production of ROS in the digestive fluid of pitcher plants at different stages of trap development is controlled by the redox modulatory system. These findings provide a basis for further research into how the regulation of ROS content supports trap development and digestive functions.