Understanding herbicide selectivity using a pharmacokinetic approach

Whilst it is known how herbicides interact with specific target sites to disrupt a particular plant process or function, how they get to the target is less well understood. Selective herbicides control target weed species whilst leaving the crop undamaged. The basis of this selectivity can be ascribed to herbicide metabolism but most of the evidence for this is taken from long term feeding experiments. We propose to use an Absorption Distribution Metabolism Excretion (ADME) dynamic approach similar to that used in drug delivery to study the uptake, translocation and detoxification of systemic herbicides in crops and weeds (wheat and black-grass) in real time. The emergence of herbicide resistance black-grass in the UK and mainland Europe is posing a growing threat to wheat yields and has the potential to result in the contamination of grains at harvest. Non-target site resistance (NTSR) in black-grass is believed to be due to enhanced metabolism of selective herbicides and by modelling the ADME of these herbicides in both wheat and black-grass (wild-type and NTSR) we should be able to understand the mechanism behind NTSR more fully.
The approach will involve the use of Rapid Evaporative Ionization Mass Spectrometry (REIMS) to allow real-time monitoring of herbicides whilst Desorption Electrospray Ionisation (DESI) mass spectrometry will be used to enable in-situ imaging of the herbicides. We then intend to couple this approach with studies using fluorescence probes coupled to bio-imaging to validate mass spectrometry methods verses optical localization of xenobiotics. Uniquely we will then generate kinetic models based on this data.