Container-grown quiescent Douglas-fir (Pseudotsuga menziesii var. glau
ca (Beissn.) Franco) seedlings were air dried to plant water potential
s of -0.2, -2.2 or -3.8 MPa (unstressed, moderate, and severe stress t
reatments, respectively). Trees from each treatment were either placed
in root mist chambers held at 10, 20, or 28 degrees C for 28 days and
root growth potential (RGP) and plant water potential (PWP) measured
weekly, or potted in a 1/1 mix of peat and vermiculite, watered only o
nce, and height growth and survival recorded after 10 weeks in an unhe
ated greenhouse. Root growth potential of unstressed trees was greater
than that of moderately stressed trees at all temperatures. Root grow
th potential of severely stressed trees was zero. Predawn plant water
potentials of unstressed and moderately stressed trees were initially
high, fell to -0.5 to -0.8 MPa, and then increased. Predawn plant wate
r potential of severely stressed trees declined continuously over the
28-day experiment. Survival and height growth of the severely stressed
trees were reduced compared to the unstressed and moderately stressed
trees. Among the root growth potential measurements, RGP measured aft
er 7 days at 10 degrees C was most sensitive to drought stress history
and revealed differences in vigor that were not apparent from the sur
vival and height growth data.