Application of methyl jasmonate on Picea abies (Pinaceae) stems induces defense‐related responses in phloem and xylem

Application of 100 mmol/L methyl jasmonate (MJ) to the intact bark of 30‐yr‐old Norway spruce induced anatomical reactions related to defense. Within 30 d, a single MJ treatment induced swelling of existing polyphenolic parenchyma cells (PP cells) and an increase in their phenolic contents and formation of additional PP cells and of traumatic resin ducts (TDs) at the cambial zone. These changes occurred up to 7 cm away from the application zone. Treatment enhanced resin flow and increased resistance to the blue‐stain fungus, Ceratocystis polonica . Methyl jasmonate application to the oldest internode of 2‐yr‐old saplings also induced TD formation, and, more surprisingly, TDs were formed in the untreated internode. Traumatic ducts were not formed in branches, ruling out an effect of volatile MJ on the upper internode. Methyl jasmonate application never gave rise to a hypersensitive response, cell death, tissue necrosis, or wound periderm, indicating the amount of MJ transported across the periderm was very low relative to the application concentration. This is the first report of a single compound giving rise to major cellular features related to acquired resistance and previously shown to be induced by wounding, fungal infection, and bark beetles in Norway spruce.