Abstract
Norway spruce is a conifer storing large amounts of terpenoids in resin
ducts of various tissues. Parts of the terpenoids stored in needles can
be emitted together with de novo synthesized terpenoids. Since previous
studies provided hints on xylem transported terpenoids as a third
emission source, we tested if terpenoids are transported in xylem sap of
Norway spruce. We further aimed at understanding if they might
contribute to terpenoid emission from needles. We determined terpenoid
content and composition in xylem sap, needles, bark, wood and roots of
field grown trees, as well as terpenoid emissions from needles. We found
considerable amounts of terpenoids – mainly oxygenated compounds - in
xylem sap. The terpenoid concentration in xylem sap was relatively low
compared to the content in other tissues where terpenoids are stored in
resin ducts. Importantly, the terpenoid composition in the xylem sap
greatly differed from the composition in wood, bark or roots suggesting
that an internal transport of terpenoids takes place at the sites of
xylem loading. Our work gives hints that plant internal transport of
terpenoids exists within conifers; studies on their functions should be
a focus of future research.