Chair of Ecosystem Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
Plant Cell Environ. 2020 Jul;43(7):1766-1778. doi: 10.1111/pce.13763. Epub 2020 Apr 12.
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 with 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. Four terpenoids were identified in xylem sap and emissions, but not within needle tissue, suggesting that these compounds are likely derived from xylem sap. Our work gives hints that plant internal transport of terpenoids exists within conifers; studies on their functions should be a focus of future research.
挪威云杉是一种含有大量萜类化合物的针叶树，这些萜类化合物储存在各种组织的树脂管中。储存在针叶中的部分萜类化合物可以与新合成的萜类化合物一起释放出来。由于之前的研究表明木质部运输的萜类化合物是第三大释放源，我们测试了挪威云杉的木质部汁液中是否存在萜类化合物运输。我们进一步旨在了解它们是否可能有助于针叶中的萜类化合物排放。我们测定了田间生长树木的木质部汁液、针叶、树皮、木材和根中的萜类化合物含量和组成，以及针叶中的萜类化合物排放。我们发现木质部汁液中含有相当数量的萜类化合物——主要是含氧化合物。与其他组织（萜类化合物储存在树脂管中）相比，木质部汁液中的萜类化合物浓度相对较低。重要的是，木质部汁液中的萜类化合物组成与木材、树皮或根中的组成有很大差异，这表明萜类化合物在木质部装载部位发生了内部运输。在木质部汁液和排放物中鉴定出了 4 种萜类化合物，但在针叶组织中没有鉴定出，这表明这些化合物可能来源于木质部汁液。我们的工作表明，萜类化合物在针叶树内部的植物内运输是存在的；它们的功能研究应该是未来研究的重点。
