Markov Random Field (MRF) modeling is a powerful framework allowing to formulate and to solve very complex imaging problems. This talk presents a particular case of MRF: the High Level MRF with application to root segmentation. This framework enables to formulate features based matching. The structures to recognize are assimilated to Markov Random Trees. A curves formulation aims to reduce the solution space and implement complex metrics. Results will be presented on data base and isolate images.