© 1986 Heron Publishing—Victoria, Canada
Effects of gibberellin A4 + 7 and bark-ringing on cone initiation in mature Picea sitchensis grafts
K. A. Longman (1), J. McP Dick (1), M. Mugglestone (1, 2) and R. I. Smith (1)
1. Institute of Terrestrial Ecology, Bush Estate, Penicuik. EH26 0QB, Scotland / 2. Applied Statistics Department, University of Reading, Whiteknights, Reading, RG6 2AN, England / Received December 19, 1985
Summary
Large numbers of cones (strobili) were induced in a 10-year-old plot of mature grafts of Picea sitchensis (Bong.) Carr. All trees injected with 20 mg GA4 + 7 in June initiated female and male cones in the same year. This treatment increased the number of female cones per plant 12-fold
above the controls, more than doubling the percentage of cones that were female. Complete bark-ringing (done in May of the
previous year) showed an additive effect with GA on the number of female cones formed, but a negative interaction on the number
of male cones induced. Ringing promoted male cone production most when used alone. Treatments, singly or combined, also increased
the proportion of cones that were lateral, compared with the preponderance of terminal male cones in the controls. The effects
were apparently not directly associated with alterations in vegetative vigor, although these occurred causing a reduction
in the proportion of buds containing vegetative shoots the following year. The clones differed in most characteristics, but
both sparse and prolific clones were induced to reproductive activity. Viable seed yields per tree, and notional production
from seed-orchards were enhanced almost 10-fold by GA injection, and about 4-fold by bark-ringing and GA + bark-ringing.
