The papers in this volume form the core of a meeting called Putting Plant Physiology on the Map, which took place at the University of Wales Bangor, in April 1997. The idea for the meeting came from Professor Sid Thomas, and the scientific organization was done by him and his colleagues at the Institute for Grassland and Environmental Research, Aberystwyth. The aim was to convene a small group of physiologists and geneticists who are concerned with the genetic mapping of plant physiological traits, to produce a meeting and published volume which would summarize some of the methods and results of existing mapping programmes, and more importantly to proselytize by laying out for unconverted plant physiologists the merits of taking a genetical approach. Writing as one of the unconverted, the meeting succeeded admirably: the power and utility of a genetical approach became very clear. Not only does mapping provide unequivocal answers to a range of physiological questions, it also enables one to ask questions that simply cannot be addressed by conventional physiological approaches. The progress which has been made in understanding salt tolerance, for example, adds a completely new dimension to the experiments in the classical literature.

Those with experience of putting plant physiological characteristics onto genetical maps inevitably have a language of their own, and for the newcomer the acquisition of this language is a daunting task. Since conversion was one of our aims, we have provided a chapter (Jones, Ougham & Thomas) which explains to the beginner just how maps are made, and in so doing hopefully eases the problem of acquiring the language. Virgin mappers should read this chapter first; the experienced can move straight to the rest and sample the variety of approaches which have been used.