Application of ultra-weak photon emission measurements in agriculture.

Here we report our two applications of ultra-weak photon emission (UPE) measurements in agriculture. One is to find new types of agrochemicals that potentiate plants' defense, so-called "plant activator". We first analyzed the relation between plant defense and Elicitor-Responsive Photon Emission (ERPE) using a combination of rice cells and a chitin elicitor. Pharmacological analyses clarified that ERPE was generated as a part of the chitin elicitor-responsive defense in close relation with the generation of reactive oxygen species (ROS). Then we successfully detected the activity of plant activators as the potentiation of ERPE, and developed a new screening system for plant activators based on this principle. Another UPE application is to distinguish herbicide-resistant weeds from susceptible ones by measuring UPE in weeds. In our study, it was revealed that the weed biotypes resistant to sulfonylurea (SU) herbicides, one of the major herbicide groups, showed stronger UPE than susceptible ones after an SU herbicide treatment. By further analysis with a pharmacological and RNAi study, we found that the detoxifying enzyme P450s contributed to the UPE increase in SU herbicide resistant weeds. It is considered that weeds resistant to herbicides other than SU might also be able to be distinguished from susceptible ones by UPE measurement, as long as the herbicides are subject to detoxification by P450s.