Hacke U, Sauter J J
Botanisches Institut der Christian-Albrechts-Universität zu Kiel, Ofshausenstrasse 40, D-24098, Kiel, Germany.
Oecologia. 1996 Mar;105(4):435-439. doi: 10.1007/BF00330005.
Xylem embolism in winter and spring as well as the occurrence of positive xylem pressure were monitored in several diffuse-porous and one ring-porous tree species (Fraxinus excelsior). In Acer pseudoplatanus and Betula pendula embolism reversal was associated with positive (above-atmospheric) xylem pressures that frequently occurred during a 2-month period prior to leaf expansion. In Acer high stem pressures were occasionally triggered on sunny days after a night frost. The other species investigated showed no positive xylem pressure during the monitoring period in 1995. Populus balsamifera exhibited a complete embolism reversal in 1994, but, like Fagus sylvatica, recovery was slow and incomplete in 1995. Fraxinus did not refill embolized vessels, but relied entirely on the production of new earlywood conduits in May. Populus × canadensis Moench "robusta" did not recover from embolism during the monitoring period. Under a simulated root pressure of 20 kPa however, excised branches of Populus × canadensis restored maximum hydraulic conductance within 2 days, illustrating the great influence of even small positive pressures on cnductivity recovery in spring. In the absence of positive pressure there was no substantial refilling of embolized vessels within a rehydration period of 9 days.
在几种散孔材和一种环孔材树种（欧洲白蜡树）中监测了冬春季节木质部栓塞以及木质部正压力的出现情况。在假挪威槭和垂枝桦中，栓塞逆转与叶展开前2个月期间频繁出现的正（高于大气）木质部压力有关。在槭属植物中，夜间霜冻后的晴天偶尔会引发高的茎压力。1995年监测期间，所研究的其他树种未出现木质部正压力。香脂杨在1994年表现出完全的栓塞逆转，但与欧洲山毛榉一样，1995年恢复缓慢且不完全。白蜡树未重新填充栓塞的导管，而是完全依赖于5月份新的早材导管的产生。加杨“健壮型”在监测期间未从栓塞中恢复。然而，在20 kPa的模拟根压下，加杨的离体枝条在2天内恢复了最大水力导度，这表明即使是很小的正压力对春季导度恢复也有很大影响。在没有正压力的情况下，在9天的复水期内，栓塞的导管没有大量重新填充。
