© 2004 Heron Publishing—Victoria, Canada
Induction of anatomically based defense responses in stems of diverse conifers by methyl jasmonate: a phylogenetic perspective
J. W. Hudgins (1), Erik Christiansen (2) and Vincent R. Franceschi (1, 3)
1. School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA / 2. Department of Forest Ecology, Norwegian Forest Research Institute, N-1432 Ås, Norway / 3. Corresponding author (vfrances@mail.wsu.edu) / Received May 21, 2003; accepted July 20, 2003; published online January 2, 2004
Summary
Conifers have evolved constitutive and inducible defense mechanisms to help in both wound healing and defense against attack
by bark beetles and other organisms. These defenses include oleoresin, phenolics, and static structures in secondary phloem,
such as lignified cells and calcium oxalate crystals, that create physical barriers. We used a phylogenetic approach to investigate
the defense anatomy of conifer stems of 13 species from five families following treatment with methyl jasmonate (MJ), a compound
that induces defense responses in stems of several Pinaceae species. Methyl jasmonate induced a response similar to wounding
except that the response was not accompanied by lesion formation, necrosis or a hypersensitive response. In the Pinaceae species
studied, MJ induced polyphenolic parenchyma (PP) cell activation and xylem traumatic resin duct (TD) formation. Members of
the Taxodiaceae, which are not known to produce large quantities of resin, showed massive xylem TD formation and surface resinosis
following MJ treatment. Treatment with MJ caused members of the Araucariaceae and Cupressaceae to form axial phloem resin
ducts but not xylem ducts, whereas Podocarpaceae species showed no induction of resin-producing structures. All species treated
with MJ showed phenolic deposition in PP cells, and early lignification of phloem fibers was observed in most of the non-Pinaceae
species. We conclude that, although evolution of resin-producing structures occurred independently in conifer lineages, MJ
seems to induce resin production regardless of tissue location, as well as inducing deposition of phenolic compounds. Co-evolution
of conifer defensive strategies and bark beetle pests is discussed.
Keywords:
bark, fibers, lignin, phenolics, plant defense, resin ducts, secondary phloem, signaling, terpenoids, xylem.
