© 1997 Heron Publishing—Victoria, Canada
Root cold tolerance of black spruce seedlings: viability tests in relation to survival and regrowth
F. J. Bigras
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, P.O. Box 3800, Sainte-Foy, Québec G1V 4C7,
Canada / Received March 25, 1996
Summary
Root systems of 6-month-old, cold-hardened, container-grown black spruce seedlings (Picea mariana (Mill.) B.S.P.) were exposed to 0, –5, –10, –15, –20, or –22.5 °C. Freezing-induced damage to fine roots, coarse roots and
the whole root system was assessed by various viability tests including leakage of electrolytes, leakage of phenolic compounds,
water loss, root and shoot water potentials, and live root dry mass. To assess the long-term effects of freezing-induced root
damage, seedling survival and regrowth were measured. Leakage of both electrolytes and phenolic compounds differed among fine
roots, coarse roots, and whole root systems. In coarse roots and the whole root system, but not in fine roots, leakage of
electrolytes, leakage of phenolic compounds, water loss, and root and shoot water potentials were correlated with percentage
of live root dry mass which, in turn, was highly correlated with seedling survival and regrowth. Compared with live root dry
mass, electrolyte and phenolic leakage, water loss, and root and shoot water potentials were less well correlated with seedling
survival and regrowth. Among the viability tests, electrolyte leakage of the whole root system correlated most closely with
seedling survival and regrowth. Under freezing conditions that destroyed less than 50% of each seedling’s root system, about
70% of the seedlings survived and subsequent growth was little affected, whereas under freezing conditions that destroyed
70% of each seedling’s root system, only about 30% of the seedlings survived and subsequent growth was reduced compared with
that of undamaged plants.
Keywords:
electrolyte leakage, phenolic leakage, Picea mariana, water loss, water potential.
