© 1997 Heron Publishing—Victoria, Canada
Effects of cone-induction treatments on black spruce (Picea mariana) current-year needle development and gas exchange properties
Ronald F. Smith (1) and Michael S. Greenwood (2)
1. Canadian Forest Service–Atlantic Forestry Centre, P.O. Box 4000, Fredericton, N.B. E3B 5P7, Canada / 2. Department of Forest Ecosystem Science, University of Maine, Orono, ME 04469, USA / Received December 20, 1995
Summary
Both drought and root pruning (RP) increased the number of cones induced when black spruce (Picea mariana (Mill.) B.S.P.) grafts were injected with gibberellins A4/7 (GA), but their effects on predawn shoot water potential and current-year needle development differed. Drought decreased
predawn shoot water potential (Ψpd), but only during the period when irrigation was withheld, and it had no effect on the growth or gas exchange properties
of current-year needles. Conversely, root pruning had little effect on Ψpd, but it resulted in trees with smaller current-year needles that had lower nitrogen and chlorophyll concentrations and reduced
rates of gas exchange up to the later stages of shoot elongation compared with needles of control trees. These findings are
discussed in relation to potential effects on the development of induced cones in the following growth cycle.
Keywords:
drought, GA4/7, photosynthesis, pollen-cone production, root pruning, seed-cone production, shoot water potential, stomatal conductance.
