Real-Time Monitoring of Pesticide Translocation in Tomato Plants by Surface-Enhanced Raman Spectroscopy

Understanding the behavior of pesticide translocation is significant for effectively applying pesticides and reducing pesticide exposures from treated plants. Herein, we applied surface enhanced Raman spectroscopy (SERS) for real-time monitoring of pesticide translocation in tomato plant tissues, including leaves and flowers, following root exposure in hydroponic and soil systems. Various concentrations of the systemic pesticide, thiabendazole, was introduced into hydroponic systems used for growing tomato plants. At selected time intervals, tomato leaves and flowers were picked and thiabendazole was measured directly under a Raman microscope after pipetting gold nanoparticle-containing solution onto the plant tissue. We found that the pesticide signals first appeared along the midrib in the lowest leaves and moved distally to the edge of the leaves. As the concentration of pesticide applied to the root was increased, the time necessary to detect the signal was decreased. The SERS surface mapping method was also able to detect thiabendazole in the trichomes of the leaves. In addition, we found a unique SERS peak at 737 cm(-1) on both leaves and flowers at 4 and 6 days following the application of 200 mg/L thiabendazole to the hydroponic system. This peak appears to be coming from adenine-containing materials and may be related to the plant's response to pesticide toxicity, which could be used as a potential marker for monitoring plant responses to stresses. These results demonstrate a successful application of SERS as a rapid and effective way to study the real-time translocation behavior of pesticides in a plant system.