Xylem dysfunction during winter and recovery of hydraulic conductivity in diffuse-porous and ring-porous trees

Abstract

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.

Climate-tree-growth relationships ofQuercus petraeaMill. stand in the Forest of Bercé (“Futaie des Clos”, Sarthe, France)

“…Spring mobilization of carbohydrates reserves in oak may be related to its hydraulic properties. The large vessels in oaks are very sensitive to winter embolism [21,51]. A large part of the previous year's earlywood vessels are embolized by frost events in winter; therefore, the production of new earlywood large vessels before leaf expansion is necessary for the spring recovery of hydraulic conductivity [10,13].…”

Uptake of Water via Branches Helps Timberline Conifers Refill Embolized Xylem in Late Winter

“…Repair of the hydraulic system may be based on the formation of new xylem or on refilling of dysfunctional xylem conduits. Several tree species can facilitate the latter by creation of positive pressures in the roots or the stem (Sperry et al, 1988b;Hacke and Sauter, 1996), but refilling has also been reported to take place at negative C (Zwieniecki and Holbrook, 2009;Nardini et al, 2011;Brodersen and McElrone, 2013;Zwieniecki et al, 2013). Although the underlying mechanism is not yet understood, the following factors have been implicated to be involved (Holbrook and Zwieniecki, 1999;Hacke and Sperry, 2003;Zwieniecki and Holbrook, 2009;Nardini et al, 2011): isolation of refilling conduits from functional ones, a pathway and a driving force allowing water shifts into embolized conduits, a source of water increasing C in conduits, as well as signal transduction networks initiating and integrating the process.…”

Annual patterns of xylem embolism in high-yield apple cultivars

“…Thus the extent to which a tree's hydraulic system is impaired during winter strongly depends on anatomical parameters of the xylem (Sperry and Sullivan 1992;Choat et al 2011), the protection against evaporative water losses (leaf shedding, cuticular and peridermal conductance (g p ) ;Larcher 2003;) and, with regard to climatic parameters, air and soil temperature, vapour pressure deficit and soil water availability. Previous studies have shown that trees in temperate regions can suffer a considerable loss of hydraulic conductance in winter (Sperry et al 1988b(Sperry et al , 1994Cochard and Tyree 1990;Sperry and Sullivan 1992;Hacke and Sauter 1996;Cochard et al 2001;Ameglio et al 2002;Mayr et al 2003;ChristensenDalsgaard and Tyree 2014). In deciduous species, though, a full water transport capacity is not required in winter and even a high level of native embolism is not particularly risky for the plant.…”

“…In several temperate trees, 6 C was found to be a critical temperature limit for root growth (Alvarez-Uria and Körner 2007). Freeze-thaw-induced embolism develops when air bubbles enclosed in frozen xylem sap expand during thawing and cause cavitation (Sperry and Sullivan 1992;Tyree et al 1994;Hacke and Sauter 1996;Cochard et al 2001;Charrier et al 2014). Two critical factors to avoid freezethaw-induced embolism are therefore conduit diameter and xylem tension: wider conduits allow the formation of larger bubbles, which shrink more slowly than smaller ones, and nucleate embolism at lower (i.e.…”