Heartwood, Discolored Wood, and Microorganisms in Living Trees

Abstract

The state of our knowledge of plant pathology is reflected by the terms we use (120). Consider some of the terms used to describe wood altered by pro­ cesses associated with aging and injury of living trees: heartwood, wound heartwood, pathological heartwood, traumatic heartwood, false heartwood, precocious heartwood, blackheart, brownheart, red heart, blue butt, mineral streak, mineral stain, woundwood, wood, wound-initiated discol­ ored wood, wetwood, ripewood, reaction zone, protection wood, and even true Indeed, there is confusion! The main visible change observed in wood of trees is change of color. This can be the result of processes associated with aging (heartwood), injury (dis­ colored wood), or both. However there are more important characteristics than color for the sapwood altered by these processes. The factors that ini­ tiate the formation of heartwood, wood, and extractives (which are largely responsible for color) are different. This is the major reason for the confusion in understanding a situation when color alone is the basis for distinguishing the type of tissue under study. When injury-altered tissues are considered as age-altered tissues, and the role of microorganisms in the processes are not considered, it is impossible to in­ terpret the situation accurately. The confusion is further compounded when the injury processes occur in tissues already altered by aging. Clarification of these processes obviously is needed. We will discuss in this review those processes in living trees that are associ­ ated with colored wood, in the hope of clarifying them so that future re­ search will be more accurately oriented and the opportunity to bring these changes under our control will be improved. We will consider and contrast two types of wood, which we will refer to as heartwood and discolored wood.