Cellular localization of chloride(Cl) and hydrogen peroxide (H2O2) in the leaf blades of maize plants exposed to 3% NaCl were investigated. This study was aimed to investigate whetherdifferential sensitivity to salinity between mesophyll cells (MC) and bundle sheath cells (BSC) in maize associated with differential accumulation of Cl and H2O2 in MC and BSC. Cl distribution was examined with X-ray microanalysis, whereas H2O2 was analyzed histochemically and cytochemically using 3,3-diamino-benzidine(DAB) and Cerium Chloride (CeCl30.The present study shows that Cl accumulation in MC and BSC of the plants treated with NaCl was relatively comparable. However, salinity-induced H2O2 formation in MC chloroplasts was higher compared with that in BSC chloroplasts. In addition, H2O2 accumulation was also detected in apoplast of MC and BSC with the greatest accumulation being detected in the cell walls of MC facing to the intercellular space. These results suggest that differential sensitivity between MC and BSC chloroplasts to salinity is not caused by differential accumulationof Cl between the cells. Apoplastic accumulation of H2O2 may rather reflect changes in oxidative balance generated by ROS scavenger in the cells that affects the homeostasis of the whole cell
