The enhanced accumulation of Pro in leaves may represent a major
biochemical adaptation, membrane stabilization and ROS scavenger. Free Pro acts as
an antioxidant in Cd-stressed cells and Pro levels are correlated with the GSH redox state and MDA
levels in heavy metal-treated algae. This result agrees with the finding of Siddiqui et al., who
reported that the production of Pro was higher in Ca2+-exposed plants under heavy metal stress