Abscisic acid in leaves and roots of willow: significance for stomatal conductance

Abstract

Excised leaves and roots of willow (Salix dasyclados Wimm.) accumulated abscisic acid (ABA) in response to desiccation. The accumulation of ABA was greater in young leaves and roots than in old leaves and roots. In mature leaves, ABA accumulation was related to the severity and duration of the desiccation treatment. Water loss equal to 12% of initial fresh weight caused the ABA content of mature leaves to increase measurably within 30 min and to double in 2.5 h. The drying treatment caused significant (P = 0.05) reductions in leaf water potential and stomatal conductance. Recovery of leaf water potential to the control value occurred within 10 min of rewatering the dehydrated leaves, but recovery of stomatal conductance took an hour or longer, depending on the interval between dehydration and rewatering. The addition of ABA to the transpiration stream of well-watered excised leaves was sufficient to cause partial stomatal closure within 1 h and, depending on ABA concentration, more or less complete stomatal closure within 3 h. When the ABA solution was replaced with water, stomatal conductance increased at a rate inversely related to the concentration of the ABA solution with which the leaves had been supplied.

Effects of soil and air drought on growth, plant water status and leaf gas exchange in three Mediterranean cedar species: Cedrus atlantica, C. brevifolia and C. libani

“…This delay could be due to the accumulation of abscisic acid (ABA) in the needles of the plants under stress. Indeed, several studies have shown that ABA plays an important role in stomatal regulation and is synthesised in the roots under water stress conditions (Bradford and Hsiao 1982; Thomas and Eamus 1999;Liu et al 2001). ABA concentrations increase with the duration and intensity of drought conditions (Fort et al 1998;Cellier et al 1998).…”

Influence of a drying cycle on post‐drought xylem sap abscisic acid and stomatal responses in young temperate deciduous angiosperms

“…Whereas leaf water potential had largely recovered within 6 h of rewatering in all five study species, g s did not recover to control levels for at least one full day. This lag in stomatal reopening after recovery of water status has also been reported in other woody species ( Vitis vinifera , Quick et al ., 1992; Litchi chinensis , Roe et al ., 1995; Salix dasyclados , Liu et al ., 2001b). Xylem sap [ABA] also recovered upon rewatering but remained two to three times above control levels at midday of Day 0, a result that may at least partly explain persistent stomatal closure early in recovery.…”

“…Further, while previous work has indicated that stomatal sensitivity to xylem [ABA] appears to increase at low Ψ (Dodd et al ., 1996), our data suggest that stomata are even more sensitive to xylem [ABA] in the recovery period than during the period of drought itself. If catabolism and/or sequestration of ABA are inhibited during the period of recovery, xylem‐transported ABA may remain elevated at the site of action in guard cells despite a return of xylem sap [ABA] to pre‐stress levels (Correia & Pereira, 1995; Liu et al ., 2001b; Wilkinson & Davies, 2002). These metabolic shifts could explain the apparent change in stomatal sensitivity to ABA in our study.…”

“…Several early experiments indicated that bulk leaf abscisic acid (ABA) concentration often recovers to pre‐drought levels before complete stomatal recovery (Beardsell & Cohen, 1975; Bengston et al ., 1977; Dörffling et al ., 1977), although there may some persistent effects of drought on apoplastic vs symplastic partitioning of leaf ABA (Loveys & Kriedemann, 1973; Cornish & Zeevaart, 1985, see also Liu et al ., 2001a). Prolonged elevation of xylem sap [ABA] is another potential source of stomatal regulation after relief from drought, as stomatal closure in a variety of herbaceous and woody species has been closely linked to elevated concentrations of ABA in the xylem sap during drought (Zhang et al ., 1987; Liang et al ., 1996; Loewenstein & Pallardy, 1998a,b; Liu et al ., 2001b). This ABA signal may be modulated by numerous environmental and endogenous factors that vary with stress, many of which appear to act through direct and indirect influences on apoplastic pH and consequent partitioning of ABA between apoplastic and symplastic compartments of the leaf (Wilkinson & Davies, 2002).…”

Drought acclimation of two deciduous tree species of different layers in a temperate forest canopy

“…The increase of [ABA] in droughted plants has repeatedly been observed (e.g. Wright 1977;Hartung and Davies 1991;Liu et al 2001;Sauter et al 2001). However, in most studies, only [ABA] of xylem sap ([ABA] xyl ) or only [ABA] of bulk leaves ([ABA] leaf ) have been measured in addition to stomatal conductance.…”