WALCK, JEFFREY L.* and SITI N. HIDAYATI. Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132. - Seed germination ecology of North American Heuchera species (Saxifragaceae): the eastern H. parviflora and western H. cylindrica.
Heuchera parviflora Bartl. var. parviflora occurs
primarily in southeastern North America and H. cylindrica
Dougl. var. cylindrica in northwestern North America. Both
species are herbaceous perennials that grow in rocky habitats. Seeds
of H. parviflora, collected in eastern Kentucky in November
1995 and 1996, and those of H. cylindrica, collected in western
Washington in August 1996, were used to test temperature and light
requirements for dormancy-break and germination and to determine
germination phenology. Fresh seeds of H. parviflora germinated
to 2-64% during 2 wk of incubation in light at alternating temperature
regimes of 15/6, 20/10, 25/15, 30/15, and 35/20oC, with
highest germination at 25/15oC; none of them germinated in
darkness. Dry storage under laboratory conditions for up to 52 wk was
not effective in overcoming dormancy. However, seeds given a 12-wk
cold stratification period at 5oC in light germinated to
76-96% in light over the range of thermoperiods but those given cold
stratification in darkness germinated to only 0-1% in darkness. Peak
germination of H. parviflora seeds sown in November 1996 in a
nonheated greenhouse occurred in early March 1997, when mean weekly
maximum and minimum temperatures were 14.8 and 8.7oC,
respectively. On the other hand, fresh seeds of H. cylindrica
germinated to 0-37% during 2 wk of incubation in light at
15/6-35/20oC, with highest germination at 15/6 and
20/10oC, and none germinated in darkness. Seeds continued
germinating to ³76% at
15/6-20/10oC during 4-12 wk of incubation in light. Neither
dry storage for up to 52 wk nor cold stratification at 5oC
for 9 wk was effective in overcoming dormancy. Peak germination of
seeds sown in the greenhouse in September 1996 occurred in late
October 1996, when mean weekly maximum and minimum temperatures were
20.7 and 11.9oC, respectively.
Key words: germination ecology, Heuchera, Saxifragaceae