© 2001 Heron Publishing—Victoria, Canada
Stomatal and leaf growth responses to partial drying of root tips in willow
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
Root tips of intact willow (Salix dasyclados Wimm., Clone 81-090) plants were partially dried by exposure to ambient greenhouse air and then kept in water-vapor-saturated
air for up to 3 days. The drying treatment increased abscisic acid (ABA) concentrations in both the root tips subjected to
drying and in the xylem sap, while it reduced leaf stomatal conductance and leaf extension rate. Despite the decrease in stomatal
conductance, leaf water potentials were unaffected by the root drying treatment, indicating that the treatment reduced hydraulic
conductivity between roots and foliage. After roots subjected to drying were returned to a nutrient solution or excised, ABA
concentrations in the remaining roots and in the xylem sap, stomatal conductance of mature leaves and extension rate of unfolding
leaves all returned to values observed in control plants. The 4-fold increase in xylem sap ABA concentration following the
root drying treatment was not solely the result of reduced sap flow, and thus may be considered a potential cause, not merely
a consequence, of the observed reduction in stomatal conductance.
Keywords:
abscisic acid, leaf extension rate, root drying, stomatal conductance, willow.
