Mechanisms of Xylem Embolism in Tree Species

植物木质部的栓塞症是指木质部导管(管胞和/或导管)充满空气，导致水分运输能力显著降低。这反过来会对植物的水分平衡造成不利影响，导致生长减慢和枯萎。在佛蒙特州北部糖枫(Aceraccharum)树的一项初步研究中，Sperry和Tyree发现，在冬季，树苗的木质部超过70%被栓塞，许多小树枝失去了对栓塞的所有水分传导能力。冬季栓塞症的逐渐恢复发生在春季，与木质部正压力的发展有关。在他们提出的研究中，Sperry和Tyree将确定冬季血栓和恢复的现象在代表环状和弥漫多孔被子植物和针叶树的共生树种中有多普遍。这将在供资期间对每个物种的栓塞率进行全年监测的情况下进行。通过现场和实验室操作，他们打算确定环境条件和栓塞症的诱导及其逆转之间的因果联系。这些信息将指导他们评估木质部栓塞在树种生态耐受性中的重要性，并解释树种死亡和衰退的时期。这项研究可能会对营林实践产生重要影响，包括建立种植园和管理现有的林分，特别是在冬季受害普遍的地区。通过确定栓塞物诱导的机制，本研究还将评估栓塞物在环境胁迫对树木健康的影响中的重要性。

Embolism in the xylem of plants is the presence of air- filled xylem conduits (tracheids and/or vessels) and it can lead to a significant reduction in water transport capacity. This in turn can adversely influence the water balance of the plant causing reduction of growth and dieback. In a preliminary study of embolism in sugar maple (Acersaccharum) trees in northern Vermont, Sperry and Tyree found that during the winter the xylem of saplings became over 70% embolized, with many small twigs losing all of their water conducting capacity to embolism. Gradual recovery from winter embolism occurred during the spring and was associated with the development of positive xylem pressures. In their proposed research, Sperry and Tyree will determine how widespread the phenomenon of winter embolism and recovery is in co-occurring tree species representing ring-and diffuse-porous angiosperms, and conifers. This will be done in the context of year-round monitoring of embolism levels for each species over the period of funding. Through field and laboratory manipulations they intend to determine the causal link between environmental conditions and the induction of embolism, as well its reversal. This information will guide them in assessing how important xylem embolism is in the ecological tolerance of tree species, and in explaining episodes of species dieback and decline. This research may have important consequences for silvicultural practices, including the establishment of plantations and management of existing stands, especially in regions where winter injury is prevalent. By determining the mechanism of embolism induction, this research will also evaluate how important embolism is in the influence of environmental stress on tree health.