Forest Ecology and Forest Management Group, Wageningen University & Research, PO Box 47, AA Wageningen, The Netherlands.
Wageningen Environmental Research, Wageningen University & Research, PO Box 47, AA Wageningen, The Netherlands.
Tree Physiol. 2019 Jun 1;39(6):1009-1018. doi: 10.1093/treephys/tpz019.
Reactivation of axial water flow in ring-porous species is a complex process related to stem water content and developmental stage of both earlywood-vessel and leaf formation. Yet empirical evidence with non-destructive methods on the dynamics of water flow resumption in relation to these mechanisms is lacking. Here we combined in vivo magnetic resonance imaging and wood-anatomical observations to monitor the dynamic changes in stem water content and flow during spring reactivation in 4-year-old pedunculate oaks (Quercus robur L.) saplings. We found that previous year latewood vessels and current year developing earlywood vessels form a functional unit for water flow during growth resumption. During spring reactivation, water flow shifted from latewood towards the new earlywood, paralleling the formation of earlywood vessels and leaves. At leaves' full expansion, volumetric water content of previous rings drastically decreased due to the near-absence of water in fibre tissue. We conclude (i) that in ring-porous oak, latewood vessels play an important hydraulic role for bridging the transition between old and new water-conducting vessels and (ii) that fibre and parenchyma provides a place for water storage.
复活动物多孔材轴向水流是一个复杂的过程，与茎含水量以及早材导管和叶形成的发育阶段都有关。然而，关于水流恢复与这些机制之间的关系，缺乏非破坏性方法的经验证据。在这里，我们结合了体内磁共振成像和木材解剖学观察，以监测 4 年生欧洲山毛榉（Quercus robur L.）幼树在春季复苏过程中茎含水量和流的动态变化。我们发现，前一年的晚材导管和当年正在发育的早材导管在生长恢复期间形成了一个功能单元，用于水流。在春季复苏期间，水流从晚材转移到新的早材，与早材导管和叶子的形成平行。在叶子完全展开时，由于纤维组织中几乎没有水，前一年的轮的体积含水量急剧下降。我们的结论是：（i）在动物多孔材栎属植物中，晚材导管在连接旧的和新的输水导管之间的过渡中起着重要的水力作用；（ii）纤维和薄壁组织为储水提供了场所。
