Hu Bin, Sakakibara Hitoshi, Takebayashi Yumiko, Peters Franziska S, Schumacher Jörg, Eiblmeier Monika, Arab Leila, Kreuzwieser Jürgen, Polle Andrea, Rennenberg Heinz
College of Forestry, Northwest A&F University, 3 Taicheng Road, 712100 Yangling, China.
Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Koehler-Allee 53/54, 79110 Freiburg, Germany.
Tree Physiol. 2017 May 1;37(5):676-691. doi: 10.1093/treephys/tpx006.
European mistletoe (Viscum album L.) has largely infested Central European forests and causes high mortality probability particularly in dry years. However, little information is available about the consequences of mistletoe infestation for metabolic processes in bark and wood of its host, despite their important roles in infestation defense. We analyzed the tissue hydration, carbohydrate composition, phytohormone profile, reactive oxygen species and anti-oxidant levels in bark and wood of Scots pines (Pinus sylvestris L.), as dependent on mistletoe infestation. As a consequence of mistletoe infestation, host bark and wood showed impaired hydration and reduced total carbon content. In the bark, soluble sugar and lignin contents increased, apparently at the expense of holo-cellulose. Hydrogen peroxide accumulation was accompanied by increased glutathione and decreased reduced ascorbic acid levels. Mistletoe infestation mediated alteration of the phytohormone profile in bark and wood of its host. Cytokinins, jasmonic acid and abscisic acid levels increased in both tissues, whereas salicylic acid and indole-3-acetic acid, which were only detected in the bark, declined. The present results show that mistletoe infestation affects both the host's anti-oxidative defense system and the phytohormone profile after establishment of the xylem tapping haustorium. The significance of these processes for the development of the woody mistletoe stem and the haustorium is discussed.
欧洲槲寄生（白果槲寄生）在中欧森林中大量滋生，尤其在干旱年份会导致树木的高死亡率。然而，尽管槲寄生的寄主树皮和木材中的代谢过程在抵御寄生方面起着重要作用，但关于槲寄生侵染对这些代谢过程影响的信息却很少。我们分析了受槲寄生侵染影响的苏格兰松树（欧洲赤松）树皮和木材中的组织水合作用、碳水化合物组成、植物激素谱、活性氧和抗氧化剂水平。由于槲寄生的侵染，寄主的树皮和木材水合作用受损，总碳含量降低。在树皮中，可溶性糖和木质素含量增加，显然是以全纤维素为代价。过氧化氢的积累伴随着谷胱甘肽的增加和还原型抗坏血酸水平的降低。槲寄生侵染介导了寄主树皮和木材中植物激素谱的改变。两种组织中的细胞分裂素、茉莉酸和脱落酸水平均升高，而仅在树皮中检测到的水杨酸和吲哚 - 3 - 乙酸水平下降。目前的结果表明，在木质部穿刺吸器建立后，槲寄生侵染会影响寄主的抗氧化防御系统和植物激素谱。本文还讨论了这些过程对木质槲寄生茎和吸器发育的意义。
