Améglio Thierry, Bodet Christian, Lacointe André, Cochard Hervé
UMR PIAF (INRA, Université Blaise-Pascal), centre INRA de Clermont-Ferrand - Theix, site de crouelle, 234, av du Brezet, 63039 Clermont-Ferrand cedex 02, France.
Tree Physiol. 2002 Dec;22(17):1211-20. doi: 10.1093/treephys/22.17.1211.
Xylem vessels of Prunus persica Batsch (peach) and Juglans regia L. (walnut) are vulnerable to frost-induced embolism. In peach, xylem embolism increased progressively over the winter, reaching a maximum of 85% loss of hydraulic conductivity (PLC) in early March. Over winter, PLC in walnut approached 100%, but the degree of xylem embolism varied during the winter, reflecting the ability of walnut to generate positive xylem pressures in winter and spring. In contrast, positive xylem pressures were not observed in peach. Controlled freeze-thaw experiments showed that frost alone is insufficient to increase embolism in peach; evaporative conditions during thawing are also required. However, when both species were protected from frost, PLC was zero. At bud break, there was complete recovery from embolism in walnut, whereas PLC remained high in peach. Three mechanisms responsible for the restoration of branch hydraulic conductivity were identified in walnut: the development of stem pressure, the development of root pressure and the formation of a new ring of functional xylem, whereas only one mechanism was observed in peach (new functional ring). The climatic conditions necessary for the manifestation of these mechanisms were investigated.
桃树（Prunus persica Batsch）和核桃树（Juglans regia L.）的木质部导管易受霜冻诱导的栓塞影响。在桃树中，木质部栓塞在冬季逐渐增加，在3月初达到最大水力传导率损失（PLC）的85%。在整个冬季，核桃树的PLC接近100%，但木质部栓塞程度在冬季有所变化，这反映了核桃树在冬季和春季产生木质部正压力的能力。相比之下，桃树中未观察到木质部正压力。控制冻融实验表明，仅霜冻不足以增加桃树的栓塞；解冻期间的蒸发条件也是必需的。然而，当两个物种都受到霜冻保护时，PLC为零。在芽萌动时，核桃树的栓塞完全恢复，而桃树的PLC仍然很高。在核桃树中确定了三种负责恢复枝条水力传导率的机制：茎压力的发展、根压力的发展和新的功能性木质部环的形成，而在桃树中只观察到一种机制（新的功能环）。研究了这些机制表现所需的气候条件。
