© 2001 Heron Publishing—Victoria, Canada
Abscisic acid in leaves and roots of willow: significance for stomatal conductance
L. Liu (1), A.J. S. McDonald (2, 5), I. Stadenberg (3) and W. J. Davies (4)
1. Department of Plant Breeding and Genetics, International Rice Research Institute, P.O. Box 933, 1099 Manila, Philippines / 2. Department of Plant and Soil Science, University of Aberdeen, Cruickshank Bldg., St. Machar Drive, Aberdeen AB24 3UU, U.K. / 3. Department of Production Ecology, Swedish University of Agricultural Sciences, P.O. Box 7042, Uppsala, Sweden / 4. Biological Sciences Department, Institute of Environmental and Natural Sciences, Lancaster University, Bailrigg, Lancaster
LA1 4YQ, U.K. / 5. Author to whom correspondence should be addressed (Jim.McDonald@abdn.ac.uk) / Received July 21, 1999
Summary
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.
Keywords:
ABA, dehydration, leaf, root, Salix dasyclados.
