Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia.
PIAF, Institut National dela Recherche Agronomique, UCA, Clermont-Ferrand, France.
Tree Physiol. 2019 Jan 1;39(1):113-121. doi: 10.1093/treephys/tpy093.
Drought stress can result in significant impairment of the plant hydraulic system via blockage of xylem conduits by gas emboli. Recovery after drought stress is an essential component of plant survival but is still a poorly understood process. In this study, we examined the capacity of woody species from two genera (Eucalyptus and Quercus) to refill embolized xylem vessels during a cycle of drought and recovery. Observations were made on intact plants of Eucalyptus calmudulensis, E. grandis, E. saligna and Quercus palustris using X-ray microtomography. We found no evidence of an effective xylem refilling mechanism in any of the plant species. Despite rehydration and recovery of plant water potential to near pre-drought levels, embolized vessels were not refilled up to 72 h after rewatering. In E. saligna, water droplets accumulated in previously air-filled vessels for a very small percentage of vessels. However, no instances of complete refilling that would restore embolized vessels to hydraulic function were observed. Our observations suggest that rapid refilling of embolized vessels after drought may not be a wide spread mechanism in woody plants and that embolism formed during drought represents long term cost to the plant hydraulic system.
干旱胁迫会通过气体栓塞阻塞木质部导管，从而对植物水力系统造成严重损害。干旱胁迫后的恢复是植物生存的重要组成部分，但仍然是一个了解甚少的过程。在这项研究中，我们研究了来自两个属（桉树属和栎属）的木本植物在干旱和恢复循环过程中重新填充栓塞木质部导管的能力。我们使用 X 射线微断层扫描对桉树属的 calmodulensis、桉树属的 grandis、桉树属的 saligna 和栎属的 palustris 进行了完整植株的观察。我们没有发现任何植物物种具有有效的木质部再填充机制的证据。尽管植物水势在重新浇水后恢复到接近干旱前的水平，但栓塞的导管在重新浇水后 72 小时内仍未被填满。在桉树属 saligna 中，只有极少数的先前充满空气的导管中积累了水滴。然而，没有观察到完全填充，即恢复栓塞导管的水力功能的情况。我们的观察结果表明，干旱后栓塞导管的快速填充可能不是木本植物中广泛存在的机制，并且干旱期间形成的栓塞代表了植物水力系统的长期成本。
