WALCK, JEFFREY L.1*, NOBUO OKAGAMI2, AND SITI N. HIDAYATI3. 1Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132; 2Faculty of Horticulture, Chiba University, Matsudo 271-8510, Japan; 3School of Biological Sciences, University of Kentucky, Lexington, KY 40506. - Germination ecophysiology of the Asian Osmorhiza aristata (Apiaceae), and comparison with its North American congeners.
Osmorhiza aristata is a herbaceous polycarpic perennial that
grows primarily from Japan, through southern China, to the Himalayas.
It is related closely to the central and eastern North American
species O. claytonii and O. longistylis. Together, the
distribution of the three species represents an example of the
well-known Asian-North American pattern of disjunction. Requirements
for dormancy-break and embryo growth were determined for seeds of
O. aristata collected in Japan during summers 1998 and 1999.
Embryos in fresh seeds were 0.48 mm long, and they had to grow to 9 mm
before the radicle emerged from the mericarp. Embryo growth and
germination occurred during cold stratification at 5 C, which was the
optimum temperature for germination. A warm (30/15 C) stratification
pretreatment was not required for seed germination at 5 C, and
gibberellic acid (GA3) did not substitute for cold
stratification. Thus, O. aristata seeds have deep complex
morphophysiological dormancy (MPD). In contrast, seeds of O.
claytonii and O. longistylis have nondeep complex MPD,
i.e., they require warm followed by cold stratification to germinate
and GA3 overcomes dormancy (Baskin & Baskin 1984, 1991).
The type of MPD in seeds of O. aristata is identical to that in
seeds of western North American populations of O. berteroi
(chilensis) and O. occidentalis (Baskin et al. 1995).
Although closely-related, Arcto-Tertiary relict congeners often
exhibit high morphological similarity (stasis), the taxa may differ
vastly in their physiological traits, such as seed dormancy.
Key words: Apiaceae, Arcto-Tertiary, Japan, North America, Osmorhiza aristata, seed germination