© 2003 Heron Publishing—Victoria, Canada
Methyl jasmonate induces changes mimicking anatomical defenses in diverse members of the Pinaceae
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. Author to whom correspondence should be addressed (vfrances@mail.wsu.edu) / Received August 2, 2002; accepted September 25, 2002; published online March 17, 2003
Summary
Conifers have defenses such as the production of phenolic compounds and resins that can be induced by bark beetles and other
invading organisms, but the signaling agents involved are unknown. The anatomical effects of methyl jasmonate (MJ), a potent
inducer of certain plant defenses, were compared with wounding of the bark of 12–15-year-old trees of five conifer species.
Wounding in all species resulted in tissue necrosis and wound periderm development immediately around the wound site. One
cm from the wound, swelling of phloem polyphenolic parenchyma cells and phenolic accumulation were observed in Pseudotsuga menziesii (Mirb.) Franco, Picea pungens Engelman, Larix occidentalis Nutt. and Pinus monticola Douglas ex D. Don, but not in Taxus brevifolia Nutt. Traumatic resin ducts were formed in response to wounding in three species of Pinaceae, but not in P. monticola, which formed irregular clusters of cells rather than ducts. Taxus brevifolia did not form resin ducts in response to either wounding or MJ treatment. In the Pinaceae species studied, surface application
of 100 mM MJ caused similar anatomical changes to those observed in response to wounding, including phenolic accumulation,
cell swelling and traumatic resin duct formation, but it did not induce a wound periderm. Traumatic resin ducts differed in
size among the study species, ranging from small in L. occidentalis to very large in P. menziesii. In P. menziesii, P. pungens and L. occidentalis, traumatic resin ducts were more abundant after MJ treatment than after wounding. We conclude that the octadecanoid pathway
is likely involved in defense responses in stems of the Pinaceae, but not necessarily in other taxa.
Keywords:
conifer, Larix occidentalis, phenolics, phloem, Picea pungens, Pinus monticola, plant defense, Pseudotsuga menziesii, resin ducts, Taxus brevifolia, xylem.
