Joint action of BASTA and Nepeta rtanjensis essential oil suppresses the effects of individual agents on Arabidopsis thaliana antioxidant system

Abstract

The present study describes the interactive effects of BASTA and Nepeta rtanjensis essential oil (NrEO), two agents showing differential mode of herbicidal action, on Arabidopsis thaliana antioxidant system. BASTA is known to act through inhibiting glutamine synthetase activity and inducing ammonium accumulation and toxicity, while NrEO and its major component nepetalactone induce oxidative stress in target plants. A. thaliana plants were exposed to BASTA through in vitro culture medium, while NrEO volatiles were supplied through the atmosphere of culture vessels. When applied independently for 10 days, BASTA (5 and 10 mg/l) and NrEO (2 and 4%), altered the activity and abundance of catalase (CAT) and peroxidase (POX) in 4 weeks old A. thaliana plants. The decrease in CAT activity in A. thaliana shoots and roots induced by NrEO treatment was followed by a decrease in CAT abundance. On the other hand BASTA induced significant increase in both CAT activity and abundance in roots. Similar trend, which was more pronounced in roots, was observed for POX activity. Superoxide dismutase (SOD) activity in Arabidopsis shoots and roots were not significantly affected by BASTA or NrEO treatments, although decrease and increase in Mn-SOD abundance were recorded following BASTA and NrEO application, respectively. Simultaneous application of NrEO and BASTA mitigated the effects of the two agents applied independently. This was especially evident for CAT and POX activity. The results indicate the existence of complex control mechanisms underlying BASTA interaction with NrEO, which involve the activation or inactivation of antioxidant defense system enzymes, and their regulation at the transcriptional level.