Osmorhiza aristata is an herbaceous perennial that grows primarily in Japan, through southern China, to the Himalayas. It closely resembles the eastern North American species O. claytonii and O. longistylis, and, together, the three species are an example of the well-known North American-Asian pattern of disjunction. Requirements for dormancy break and embryo growth were determined for seeds of O. aristata collected in Japan during the summers of 1998-2000. Embryos in fresh seeds were ca. 0.5 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, the optimum temperature for germination. Gibberellic acid did not substitute for cold stratification. Thus, O. aristata seeds have deep complex morphophysiological dormancy (MPD). The type of MPD in O. aristata is similar to that in two western North American congeners but different from that in eastern North American congeners (nondeep complex MPD). Mapping the types of MPD onto a phylogeny of the genus suggests that nondeep complex MPD is derived from deep complex MPD. Although eastern North American-Asian disjuncts often exhibit morphological stasis, the taxa may differ greatly in physiological traits, such as seed dormancy.

The sprouting of bulbils of some plants in genus Dioscorea was inhibited by gibberellin (GA) treatment and was promoted by treatment with growth retardants. The results suggest that endogenous GAs in some manner induce and maintain the dormant state in these bulbils.

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It is known that dormancy of the genus Dioscorea is induced by application of gibberellin (GA) A3. To understand the role of GAs in dormancy induction, endogenous GAs have been identified by Kovats retention indices and full mass spectra from capillary gas chromatography-mass spectrometry analysis of purified extract from dormant bulbils of Dioscorea opposita Thunb. These include GA4, GA9, GA12, GA19, GA20, GA24, GA36, and GA53; their presence suggests the occurrence of two biosynthetic pathways in D. opposita bulbils, the early 13-hydroxylation pathway and the non-13-hydroxylation pathway.It is well known that dormancy of many plant species (15) can be broken by application of GAs'. Endogenous GAs are believed to be a group of plant hormones that break dormancy and initiate germination and sprouting. In contrast, application of GA3 strengthens or deepens the dormancy of seeds or buds of several species (3-5, 8, 10-14, 17). Among these species, promotion of sprouting of half-dormant bulbils and subterranean tubers by inhibitors of GA biosynthesis, such as N-dimethylaminosuccinamic acid, 2-chloroethyl-trimethyl ammonium chloride, and AMO 1618 was observed in some species in the genus Dioscorea (11,12). This is also the effect of uniconazole, a triazole-type growth retardant, on bulbils of Dioscorea spp. (our unpublished data). Therefore, it is most likely that endogenous GAs are involved in induction and maintenance of dormancy of seeds (10), bulbils (11,12), and subterranean tubers (12,13) in the genus Dioscorea.Investigation of the dynamics of endogenous GAs in dormant organs is important for understanding the roles of GAs in both dormancy inducing or maintaining and dormancy breaking. However, there has been no literature concerning GA dynamics in dormant organs whose dormancy was induced either naturally, presumably by endogenous GAs, or by GA3 application. To get information necessary for understanding natural or GA-induced dormancy, we analyzed endogenous GAs in dormant bulbils of D. opposita and identified several GAs. MATERIALS AND METHODS Extraction and PurificationDormant, mature bulbils of Chinese yam, Dioscorea opposita Thunb., which naturally shed from the cultivated mother plants, were collected in November 1988 and immediately stored at -400C until extracted. As much as 51.2 kg of the bulbils were extracted three times using 200 L of acetone. The acetone was evaporated, and the resultant aqueous phase was adjusted with HCl to pH 2.4 and partitioned five times against 3.6 L of EtOAc, which was concentrated in vacuo to brown gum (26 g). This was dissolved in 500 mL of 0.1 M phosphate buffer (pH 8.0) and then loaded onto a column of polyvinylpolypyrrolidone (500 g; Tokyo Kasei Co., Tokyo, Japan). The buffer eluate (4 L) was acidified and partitioned four times against 2 L of EtOAc. The organic phases were concentrated in vacuo to 5.34 g of brown oil. This oil was dissolved in 40 mL of 70% MeOH (0.1% HOAc), loaded onto a column of ODS (100 g; Senshu Scientific Co., Ltd., Tokyo, Japan), and elu...