Pathology of the Xylem

Abstract

This chapter is probably the most difficult one for me to write, because, in doing so, I have to step outside my field of expertise more often than I like. Yet, I feel that it is necessary to build a bridge between those of us who are concerned with xylem structure and the ascent of sap, and those plant pathologists who are interested in xylem dysfunction. I hope that my colleagues in plant pathology will not take offense for my “meddling in their affairs”, but that instead this will be the beginning of a fruitful collaboration. The two groups can certainly learn a good deal from each other. I also hope that I shall hear from plant pathologists, in order to learn where my concepts are wrong and my knowledge is incomplete. This chapter is not a review of pathological disturbance of water relations in general. Such reviews are available elsewhere (e.g., Ayres 1978). There are also many aspects of xylem dysfunction that are important after conduction has ceased; these are also outside the area of interest of this book. We are concerned here only with the ascent of sap and its disturbance.