BASKIN, CAROL C.*, PER MILBERG, LARS ANDERSSON, AND JERRY M. BASKIN. School of Biological Sciences and Department of Agronomy, University of Kentucky, Lexington, KY 40506; Department of Biology-IFM, Linköping University, 581 83 Linköping, Sweden; Department of Ecology and Crop Production Science, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden; and School of Biological Sciences, University of Kentucky, Lexington, KY 40506. - Germination studies on three dwarf shrubs (Vaccinium, Ericaceae) of Northern Hemisphere coniferous forests.
Freshly-matured seeds of Vaccinium myrtillus, V. vitis-idaea
and V. uliginosum from coniferous forests in Sweden were tested
for germination in light and darkness at 12/12 h daily temperature
regimes at 15/5 (or 15/6), 20/10 and 25/15 C. Seeds also were tested
at the same conditions after they were cold stratified. In initial
tests, seeds of V. myrtillus and V. vitis-idaea
germinated to 62-100% in light at 20/10 and/or 25/15 C with few
(1-12%), or no seeds germinating at 15/5(6) C; however, after 12 or 20
wk of stratification germination percentages increased significantly
in light at 15/5(6) C. Thus, seeds of these species are conditionally
dormant at maturity. One to 20% of V. myrtillus and 0-2% of
V. vitis-idaea seeds sown outdoors in southern Sweden on various
dates in summer germinated before winter. Seeds of neither species
germinated during late May, when minimum temperatures were about 7-10
C, but they germinated after minimum temperatures increased to ³ 10 C. Stratified seeds of V. myrtillus
and V. vitis-idaea required more than 2 wk of incubation at
15/5(6) C for initiation of germination. Therefore, even after
habitat temperatures have reached the minimum range for germination of
nondormant seeds, a slow rate of germination at low temperatures may
prevent them from germinating in early spring. Nonstratified seeds of
V. uliginosum germinated to a maximum of 5% in light and of 7%
in darkness, but after 12 wk of stratification seeds germinated to
49-95% in light and to 1-60% in darkness at 15/5, 20/10 and 25/15 C.
Most seeds of V. uliginosum were dormant at maturity, and they
came out of dormancy during stratification in winter. Seeds of V.
uliginosum germinated over the same range of temperatures as those
of V. myrtillus and V. vitis-idaea by spring, but they
germinated faster at 15/5(6) C than those of the other two species.
Key words: blueberry seed germination, cold stratification, Ericaceae, seed dormancy, seed germination, Vaccinium