Discipline of Biological Sciences, School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, TAS, 7001, Australia.
New Phytol. 2022 Jan;233(1):207-218. doi: 10.1111/nph.17786. Epub 2021 Oct 29.
Damage to the plant water transport system through xylem cavitation is known to be a driver of plant death in drought conditions. However, a lack of techniques to continuously monitor xylem embolism in whole plants in vivo has hampered our ability to investigate both how this damage propagates and the possible mechanistic link between xylem damage and tissue death. Using optical and fluorescence sensors, we monitored drought-induced xylem embolism accumulation and photosynthetic damage in vivo throughout the canopy of a drought-resistant conifer, Callitris rhomboidea, during drought treatments of c. 1 month duration. We show that drought-induced damage to the xylem can be monitored in vivo in whole trees during extended periods of water stress. Under these conditions, vulnerability of the xylem to cavitation varied widely among branchlets, with photosynthetic damage only recorded once > 90% of the xylem was cavitated. The variation in branchlet vulnerability has important implications for understanding how trees like C. rhomboidea survive drought, and the high resistance of branchlets to tissue damage points to runaway cavitation as a likely driver of tissue death in C. rhomboidea branch tips.
已知植物木质部空化会损害水分运输系统，从而导致植物在干旱条件下死亡。然而，由于缺乏连续监测活体植物木质部栓塞的技术，我们无法研究这种损伤的传播方式以及木质部损伤与组织死亡之间的可能机制联系。本研究使用光学和荧光传感器，在长达约 1 个月的干旱处理过程中，监测了耐旱针叶树蓝桉树冠中木质部栓塞积累和光合作用损伤情况，结果表明可以在活体整棵树中监测到木质部在长时间水分胁迫下产生的损伤。在这些条件下，木质部对空化的脆弱性在小枝之间差异很大，只有当 > 90%的木质部发生空化时才会记录到光合作用损伤。小枝脆弱性的差异对理解像蓝桉这样的树木如何在干旱中存活具有重要意义，而小枝对组织损伤的高抗性表明，在蓝桉的枝梢中，空化失控很可能是组织死亡的驱动因素。
