Xylem transport is essential to the growth, development, and survival of vascular plants. Bark wounding may increase the risk of xylem transport failure by tension-driven embolism. However, the consequences of bark wounding for xylem transport are poorly understood. Here, we examined the impacts of the bark wounding on embolism formation, leaf water potential, and gas exchange in terminal branches of two diffuse-porous tree species (Acer platanoides L., Prunus avium L.). The effects of bark removal were examined on field-grown mature trees exposed to increased evaporative demands on a short-term and longer-term basis (6 h vs. 6 d after bark wounding). Bark removal of 30% of branch circumference had a limited effect on xylem hydraulic conductivity when embolized vessels were typically restricted to the last annual ring near the bark wound. Over the six-day exposure, the non-conductive xylem area had significantly increased in the xylem tissue underneath the bark wound (from 22-29% to 51-52% of the last annual ring area in the bark wound zone), pointing to gradual yet relatively limited embolism spreading to deeper xylem layers over time. In both species, the bark removal tended to result in a small but non-significant increase in percent loss of hydraulic conductivity compared to control intact branches six days after bark wounding (from 6% to 8-10% in both species). The bark wounding had no significant effects on midday leaf water potential, CO2 assimilation rates, stomatal conductance, and water use efficiency in leaves of the current-year shoot, possibly due to limited impacts on xylem transport. The results of this study demonstrate that bark wounding induces limited but gradual embolism spreading. However, the impacts of bark wounding may not significantly limit water delivery to distal organs and leaf gas exchange at the scale of several days.

中文翻译：

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树皮受伤会引发两种散孔树种的栓塞逐渐蔓延。

木质部运输对于维管植物的生长、发育和生存至关重要。树皮受伤可能会增加张力驱动栓塞导致木质部运输失败的风险。然而，人们对树皮受伤对木质部运输的影响知之甚少。在这里，我们研究了树皮受伤对两种散孔树种（Acer platanoides L.、Prunus avium L.）的栓塞形成、叶水势和末端树枝气体交换的影响。在短期和长期（树皮受伤后 6 小时与 6 天）暴露于增加的蒸发需求的田间生长的成熟树木上，检查了树皮去除的影响。当栓塞血管通常局限于树皮伤口附近的最后一个年轮时，去除 30% 树枝周长的树皮对木质部水力传导率的影响有限。在六天的暴露中，树皮伤口下方的木质部组织中的非导电木质部面积显着增加（从树皮伤口区域最后一个年轮面积的 22-29% 增加到 51-52%），表明随着时间的推移，逐渐但相对有限的栓塞扩散到更深的木质部层。在这两个物种中，在树皮受伤后六天，与对照完整树枝相比，树皮去除往往会导致水力传导率损失百分比小幅但不显着增加（两个物种中从 6% 增加到 8-10%）。树皮受伤对当年枝叶的中午叶水势、二氧化碳同化率、气孔导度和水分利用效率没有显着影响，可能是由于对木质部运输的影响有限。这项研究的结果表明，树皮受伤会导致有限但逐渐的栓塞扩散。然而，树皮受伤的影响可能不会显着限制向远端器官的水输送和数天范围内的叶气体交换。