Wound‐induced traumatic resin duct development in stems of Norway spruce (Pinaceae): anatomy and cytochemical traits

Abstract

Wounding of Norway spruce by inoculation with sterile agar, or agar containing the pathogenic fungus Ceratocystis polonica, induced traumatic resin duct formation in the stem. Visible anatomical responses occurred in the cambium 6-9 d post-inoculation. Near the inoculation site cellular proliferation, polyphenolic accumulation, and lignification were induced as a wound reaction to seal the damaged area. Five centimetres from the inoculation site cells in the cambial zone swelled and divided to form clusters. By 18 d post-inoculation, these cells began to differentiate into resin duct epithelial cells surrounding incipient schizogenous lumens. Mature axial traumatic ducts appeared by 36 d as a row of ducts in the xylem centripetal to the cambium. The ducts formed an interconnected network continuous with radial resin ducts. Parenchyma cells surrounding the ducts accumulated polyphenols that disappeared as the cells differentiated into tracheids. These polyphenols appeared to contain fewer sugar residues compared to those accumulating in the secondary phloem, as indicated by the periodic acid-Schiff's staining. The epithelial cells did not accumulate polyphenols but contained immunologically detectable phenylalanine ammonia lyase (EC 4.3.1.5), indicating synthesis of phenolics as a possible resin component. These findings may represent a defense mechanism in Norway spruce against the pathogenic fungus Ceratocystis polonica.

On plant defense signaling networks and early land plant evolution

“…A straightforward example of a lineage-specific defense strategy in gymnosperms is the flow of resin in wounded conifers, which depends upon resin ducts. Some resin ducts are formed during plant growth and flooded with resin in response to stress, while other resin ducts are only induced upon infection and wounding through the action of phytohormones [15-17]. By exploring the commonalities and differences, we will highlight both the evolutionary trajectories and underlying principles of land plant signaling upon phytopathogen attack – including the potential for this signaling in streptophyte algae.…”

Methyl Jasmonate Induces Traumatic Resin Ducts, Terpenoid Resin Biosynthesis, and Terpenoid Accumulation in Developing Xylem of Norway Spruce Stems

“…De novo formation of resin ducts in the developing xylem has been described as a possible resistance mechanism against insects and pathogens in white spruce (Picea glauca), Sitka spruce (Picea sitchensis), and Norway spruce (Alfaro, 1995;Tomlin et al, 1998;Franceschi et al, 2000).…”

“…Formation of TDs in spruce is elicited by stemboring insects and microbial pathogens as a defense response that can also be induced by mechanical wounding or by wounding and fungal inoculation of trees (Alfaro, 1995;Tomlin et al, 1998Tomlin et al, , 2000Franceschi et al, 2000). Because wounding of trees can cause massive bleeding and volatilization of oleoresin and disruption of the tissues that are possibly involved in de novo resin formation, it was important to develop a noninvasive method for TD induction to enable a detailed chemical and biochemical analysis of the traumatic resin response.…”

“…Previous studies of the anatomy and resin chemistry of TDs in spruce involved mechanical wounding or fungal inoculation of trees as a means to induce TD formation (Alfaro, 1995;Tomlin et al, 1998Tomlin et al, , 2000Franceschi et al, 2000). In this study, we developed a noninvasive procedure for TD induction in Norway spruce based on topical application of methyljasmonate (MeJA).…”

“…3). Recent microscopic work with Norway spruce has described details of the TD formation (Nagy et al, 2000). The production of TDs is due to a change in the developmental program of cambial activity whereby some of the xylem mother cells initiate epithelial cells (which eventually come to surround the TD lumen) in lieu of tracheids.…”