Plant Stems

Plant Stems

Physiology and Functional Morphology
Physiological Ecology
1995, Pages 383-406
Plant Stems

17 - Stem Defense against Pathogens

https://doi.org/10.1016/B978-012276460-8/50019-9Get rights and content

Publisher Summary

This chapter focuses on how trees, particularly tree stems, defend themselves against fungal pathogens. A treatise on the defense of trees as a whole against fungi may be found and information regarding the defense of stems against herbivores is provided. Numerous mechanisms have been proposed for host defense. Defense mechanisms are described as either passive if they occur prior to an infection or active if they are induced during the infection process. Passive and active mechanisms are further subdivided into anatomical or physical barriers, and chemical barriers. These mechanisms are well explained here. It is thought that the binding of these elicitors to receptors initiates a cascade of metabolic events that results in the activation and expression of defense genes and their products. It has been proposed that sapwood defense can be explained solely by its high moisture content and concomitant reduced aeration. A number of active mechanisms have been proposed to explain sapwood defense. The mechanisms of signal transduction and protection of xylem produced years after wounding by a nondescript barrier are challenging questions for the investigator. Heartwood is the dead central core of trees. It is formed as a result of senescence of inner sapwood parenchyma. Evidence supporting the role(s) of proposed resistance mechanisms in defense is largely circumstantial, but in some cases compelling.

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