The Handbook of Plant Ecophysiology Techniques you have now in your hands is the result of several combined events and efforts. The birth of this handbook can be traced as far as 1997, when our Plant Ecophysiology lab at the University of Vigo hosted a practical course on Plant Ecophysiology Techniques. That course showed us how much useful a handbook presenting a bunch of techniques would be for the scientists beginning to work on Plant Ecophysiology. In fact, we wrote a short handbook explaining the basics of the techniques taught in that 1997 course: Flow cytometry to measure ploidy levels, Use of a Steady-State porometer to measure transpiration, In vivo measure of fluorescence, HPLC analysis of low molecular weight phenolics, Spectrophotometric determinations of free proline and soluble proteins, TLC polyamines contents measures, Isoenzymatic electrophoresis, Use of IRGA and oxygen electrode. That modest handbook, written in Spanish, was very helpful, both for the people who attended the course and for other who have used it for beginning to work in Plant Ecophysiology. The present Handbook is much more ambitious, and it includes more techniques. But we have also had in mind the young scientists beginning to work on Plant Ecophysiology. In 1999 François Pellissier leaded a proposal presented to the European Commission in the Fifth Framework Program in the High Level * Scientific Conferences, including three EuroLab Courses about lab and field techniques useful to improve allelopathic research.