© 1991 Heron Publishing—Victoria, Canada
Clonal variation of Populus tremuloides responses to diurnal drought stress
David H. Griffin, Michail Schaedle, Michael J. DeVit and Paul D. Manion
Faculty of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry,
Syracuse, New York 13210, USA / Received May 30, 1990
Summary
We have developed an automated microprocessor controlled system for subjecting hydroponically grown plants to drought. Pumps
and valves were used to move nutrient solutions into and out of a system of culture vessels in a growth chamber to provide
periods of drought. Drought conditions were obtained by exposing the roots of hydroponically grown clones of aspen, Populus tremuloides Michx., to air in culture vessels temporarily emptied of nutrient medium. Over a 3-week period, the daily duration of drought
was increased from 0 to 6 h. During this period, the plants became increasingly tolerant to drought, as shown by a decreasing
propensity to wilt. All three clones sustained diurnal drought periods of 6 h for up to 5 weeks without detectable deterioration
of health. Typical drought stress symptoms were observed including inhibition of growth, increased tissue amino acid content,
and decreased water, solute, and turgor potentials in young leaves.
In all clones, control plants had leaf water potentials between –1.0 and –1.6 MPa, whereas leaf water potentials of drought-treated
plants were significantly lower, ranging from –1.7 to –3.0 MPa. Only one of the clones showed a significant decrease in leaf
solute potential in response to drought. The decrease in leaf solute potential paralleled the decrease in water potential
resulting in no significant difference in turgor potential. The other two clones had nonsignificant decreases to more negative
leaf solute potentials under drought conditions resulting in significantly lowered turgor potentials. Leaf water potentials,
solute potentials, and turgor potentials of the drought-treated plants returned to control values within two hours after rewatering.
The growth inhibitions observed could not have been the consequence of loss of turgor. These results demonstrate genetic differences
among aspen clones in water relations responses to drought.
