Stress Effects of TiO2 and NP-TiO2 on Catalase Enzyme and some Physiological Characteristics of Melissa officinalis L.

Aims: Today, detection of risk effects of metal and metal nanoparticles over environment has attracted much attention. Plants are always exposed to considerable nanoparticles. So we decided to study the stress effect of titanium dioxide (TiO2) and titanium dioxide nanoparticles (NP-TiO2) phytotoxicity on catalase (CAT) enzyme and some physiological characteristics of Melissa officinalis L. plant including germination, root length, shoot length, and photosynthetic pigments.

Place and Duration of Study: The experiment was conducted in 2013 in the Research Laboratory of Islamic Azad University of Falavarjan, Isfahan, Iran.

Methodology: Seeds were treated with solutions of TiO2 and NP-TiO2 in 4 replicates. The obtained results were the mean of 4 replicates±SD. Finally the results were analyzed using SPSS18 statistical software.

Results: The results indicated that different treatments of TiO2 and NP-TiO2 compared to the control group had no significant effect on germination percentage. However, they had a positive effect on root length, shoot length, and photosynthetic pigments (chlorophylls and carotenoids). At low concentrations, TiO2 and NP-TiO2 had a stimulatory effect on all parameters except the germination. NP-TiO2 had increase effect on CAT activity and TiO2 had the decrease effect on it.

Conclusion: The ROS stress which produce by NPs, can stimulated the antioxidant enzymes in plants. In this article, the ROS stress had increased effect on CAT activity. To understand the positive and negative effects of nanoparticles on other physiological characteristics of Melissa officinalis L. requires further investigation.