© 2005 Heron Publishing—Victoria, Canada
Elevated temperature during reproductive development affects cone traits and progeny performance in Picea glauca × engelmannii complex
Joe Webber (1, 2), Peter Ott (3), John Owens (4) and Wolfgang Binder (1)
1. British Columbia Ministry of Forests, Research Branch, P.O. Box 9536, Station Provincial Government, Victoria, BC V8W 9C4,
Canada / 2. Corresponding author (jwebber@saltspring.com) / 3. British Columbia Ministry of Forests, Research Branch, 3rd Floor, 712 Yates Street, P.O. Box 9519, Station Provincial Government,
Victoria, BC V8W 9C2, Canada / 4. Centre for Forest Biology, University of Victoria, P.O. Box 3020, Station CSC, Victoria, BC V8W 3N5, Canada / Received December 2, 2004; accepted March 5, 2005; published online August 1, 2005
Summary
Two temperature regimes were applied during reproductive development of seed and pollen cones of interior spruce (Picea glauca (Moench) Voss and Picea engelmannii (Parry) complex) to determine temperature effects on the adaptive traits of progeny. In Experiment 1, identical crosses were
made on potted interior spruce using untreated pollen followed by exposure to a day/night temperature of 22/8 or 14/8 °C with
a 12-h photoperiod during the stages of reproductive development from post-pollination to early embryo development. Frost
hardiness and growth of progeny from seed produced in the two temperature treatments were measured over a 4-year period. Elevated
temperature significantly affected both seed-cone development and the adaptive properties of the progeny. Seed cones exposed
to the 22/8 °C treatment reached the early embryo stage in 53 days versus 92 days in the 14/8 °C treatment. Seed yields, cotyledon
emergence and percent germination were also significantly enhanced by the 22/8 °C treatment. Progeny from seed produced in
the higher temperature treatment showed significantly reduced spring and fall frost hardiness, but the elevated temperature
treatment had no significant effects on time of bud burst, growth patterns or final heights. In Experiment 2, single ramets
of the same clone were subjected to a day/night temperature of 20/8 or 10/8 °C during pollen cone development, starting from
meiosis and ending at pollen shedding. The two populations of pollen were then crossed with untreated seed cones. Compared
with pollen cones exposed to the 10/8 °C treatment, pollen cones exposed to the 20/8 °C treatment during development reached
the shedding stage 2–4 weeks earlier, whereas pollen yields, in vitro viability and fertility (seed set) were significantly
lower; however, the resulting progeny displayed no treatment differences in frost hardiness or growth after 1 year. Results
suggest that seed orchard after-effects could be caused by temperature differences between orchard site and parent tree origin
and that this effect acts on maternal development. Gametophytic (pollen or megagametophyte or both) and early embryo (sporophytic)
selection are possible mechanisms that may explain the observed results. Although the effects are biologically significant,
they are relatively small and do not justify changes in current deployment strategies for seed orchard seed.
Keywords:
after-effects, gametophytic selection, maternal environment, pollen cone, seed cone, seed orchard, white spruce.
