© 1991 Heron Publishing—Victoria, Canada
Fall lifting and long-term freezer storage of ponderosa pine seedlings: effects on post-storage leaf water potential, stomatal
conductance, and root growth potential
S. K. Omi, B. Yoder and R. Rose
Department of Forest Science, Oregon State University, Corvallis, Oregon 97331-5705, USA / Received June 7, 1990
Summary
Post-storage water relations, stomatal conductance, and root growth potential were examined in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings from high- and low-elevation seed sources that had been lifted either in October or November and
freezer stored, or in March, and then grown hydroponically in a greenhouse for 31 days. Seedlings lifted in October had poor
root initiation (< 17 new roots per seedling), low predawn leaf water potentials (< –1.5 MPa), and low stomatal conductance
(7.10 mmol m–2 s–1) compared with seedlings lifted in November or March. There was little difference in post-storage water relations and stomatal
conductance between seedlings lifted in November and those lifted in March. Throughout the 31-day test, seedlings from the
high-elevation seed source produced 3–9 times more new roots, had higher predawn leaf water potentials (–0.6 to –0.7 MPa versus
–1.1 to –1.6 MPa), and 1.3–5 times greater stomatal conductance than seedlings from the low-elevation seed source. For all
seedlings on Day 31, the number of new roots was significantly related to predawn leaf water potential (r2 = 0.65) and stomatal conductance (r2 = 0.82). Similarly, the dry weight of new roots per seedling on Day 31 accounted for a significant amount of the variation
in predawn leaf water potential (r2 = 0.81) and stomatal conductance (r2 = 0.49).
