The foliar concentration of hydrogen peroxide during salt-induced C3-CAM transition in Mesembryanthemum crystallinum L

Hydrogen peroxide (H2O2) is one of the most stable reactive oxygen species (ROS), which is produced in plants in various metabolic processes and its level can increase as a result of many stress factors. It was found that a NaCl-induced shift from C-3 to CAM in Mesembryanthemum crystallinum L. leaves was accompanied with a significant increase in H2O2 concentration (as calculated on a chlorophyll basis). Moreover, the highest accumulation of H2O2 in leaves and leaf veins appeared before the maximal nocturnal malate accumulation was detected on day 6 and 9 of NaCl-treatment, indicating that salinity itself is responsible for an increase in H2O2 production. Several symptoms of functional CAM, i.e. strong increase in NADP-ME activity, and diel malate oscillations, appeared after 9-12 days of salt-treatment. The obtained results suggest that accumulation of H2O2 in leaves and leaf veins is due to salinity itself, and appears before functional CAM, but H2O2 as a trigger involved in C-3-CAM transition seems to be an important factor. (c) 2007 Elsevier Ireland Ltd. All rights reserved.