Stewart Jared J, Allen Brendan S, Polutchko Stephanie K, Ocheltree Troy W, Gleason Sean M
Water Management and Systems Research Unit, Agricultural Research Service, United States Department of Agriculture, Fort Collins, CO 80526.
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309.
Proc Natl Acad Sci U S A. 2025 Apr;122(13):e2420618122. doi: 10.1073/pnas.2420618122. Epub 2025 Mar 20.
Plant hydraulic dysfunction by embolism formation can impair photosynthesis, growth, and reproduction and, in severe cases, lead to death. Embolism reversal, or "refilling," is a hypothesized adaptive process in which xylem functionality is rapidly and sustainably restored. This study investigated xylem embolism refilling during recovery from severe drought stress using entirely noninvasive measurements of the same plants. These results were considered in relation to functional traits to address long-standing gaps in understanding the consequences of severe drought stress. Leaf and stem xylem embolism as well as transpiration, photosynthesis, and stem water potential were characterized nondestructively on intact barnyard grass plants during an acute drought event. Plants were rewatered and returned to growth conditions for 10 d, during which time recovery of stem xylem embolism and transpiration were monitored. Leaf xylem embolism and declines in leaf gas exchange occurred mostly between -1.0 MPa and -2.0 MPa, whereas stem xylem embolism occurred mostly between -3.0 MPa and -4.0 MPa. In all measured plants, which included embolism levels up to 88%, stem xylem embolism reversed completely within 24 h after rewatering, and this refilling supported recovery of transpiration and growth after plants were returned to growth conditions. This study provides direct evidence of complete and functional stem xylem refilling. These results present a clear need to elucidate underlying mechanisms and the adaptive significance of this phenomenon as well as its prevalence in nature.
栓塞形成导致的植物水力功能障碍会损害光合作用、生长和繁殖，严重时会导致植物死亡。栓塞逆转，即“再充盈”，是一种假设的适应性过程，在这个过程中木质部功能能够迅速且持续地恢复。本研究使用对同一植物完全非侵入性的测量方法，调查了严重干旱胁迫恢复过程中的木质部栓塞再充盈情况。结合功能性状对这些结果进行了考量，以填补长期以来在理解严重干旱胁迫后果方面存在的空白。在急性干旱事件期间，对完整稗草植株的叶片和茎木质部栓塞以及蒸腾作用、光合作用和茎水势进行了无损表征。给植物重新浇水并使其恢复生长状态10天，在此期间监测茎木质部栓塞和蒸腾作用的恢复情况。叶片木质部栓塞和叶片气体交换的下降大多发生在-1.0兆帕至-2.0兆帕之间，而茎木质部栓塞大多发生在-3.0兆帕至-4.0兆帕之间。在所有测量的植株中，包括栓塞水平高达88%的植株，重新浇水后24小时内茎木质部栓塞完全逆转，这种再充盈支持了植物恢复生长状态后蒸腾作用和生长的恢复。本研究提供了茎木质部完全且功能性再充盈的直接证据。这些结果明确表明，有必要阐明这一现象的潜在机制、适应性意义及其在自然界中的普遍性。
