Oxidative stress enzymes in Ficus religiosa L.: Biochemical, histochemical and anatomical evidences

In order to unveil the reasons behind the successful survival of Ficus religiosa L. grown under normal and adverse habitats (AH), i.e., on concrete roof tops were subjected to biochemical, histochemical and physiological studies with a focus on reactive oxygen species (ROS) and oxidative stress enzymes (OSE). The specific objectives were: to localize the OSE, peroxidase (POX) and catalase (CAT); to localize and quantify the main ROS, hydrogen peroxide (H2O2); to estimate the activities of POX, CAT and glycolate oxidase (GO); and to study the diurnal variations in stomatal activity by scanning electron microscopy (SEM). From the results, plants grown in AH showed 55% higher H2O2 production with about 30% increase in POX activity. Of the three substrates tested for POX activity (guaiacol, ascorbate and o-dianisidine), o-dianisidine was found as the preferred substrate of F. religiosa POX with about 7-fold more activity over its counterparts. Cytosolic POX activity showed 11-fold increase over cell wall bound POX. Similarly, CAT activity in specimens from AH showed about 2-fold increase during day time. The physiological interaction between CAT and its substrate H2O2 in the plant was determined by quantifying H2O2 and assaying the CAT, in which CAT showed 4-fold increases in activity, especially during night. F. religiosa has higher amount of H2O2 deposition during night than day time, which was in correlation high CAT activity during night, coupled with scotoactive opening of stomata as shown by the SEM images. Moreover, GO did not show much habitat-dependent variation. In toto, F. religiosa grown in AH showed elevated production of ROS and their scavenging OSE, which is the direct evidence for drought stress and also giving an insight into its evolution and ecological niche.