American Journal of Botany 89(11): 1779±1784. 2002.

ECOPHYSIOLOGY OF SEED GERMINATION IN JAPONICUM () WITH UNDERDEVELOPED EMBRYOS1

TETSUYA KONDO,2,4 NORI OKUBO,2 TAKU MIURA,2 KAZUSHIGE HONDA,3 AND YUKIO ISHIKAWA3

2Graduate School of Agriculture, Hokkaido University, Kita-ku, Sapporo 060-8589, ; 3Department of Forestry and Landscape Architecture, Hokkaido College, Senshu University, Bibai 079-0197, Japan

Erythronium japonicum (Liliaceae) (Japanese name, katakuri) is indigenous to Japan and adjacent Far East regions. We examined their embryo elongation, germination, and seedling emergence in relationship to the temperature. In incubators, seeds did not germinate at 20Њ/10Њ (light 12 h/dark 12 h alternating temperature), 20Њ,15Њ,5Њ,or0ЊC with a 12-h light photoperiod for 200 d. They germinated at 15Њ/5Њ or 10ЊC, starting on day 135. If seeds were kept at 20Њ or at 25Њ/15ЊC before being exposed to 5ЊC, the seeds germinated, but if kept at 25Њ or 30ЊC they did not. Embryos at 25Њ/15ЊC grew to half the seed length without germinating; at 0Њ or 5ЊC, embryos elongated little. Embryos grew and seeds germinated when kept at 25Њ/15ЊC for 90 d and then at 5ЊC. In the ®eld, seeds are dispersed in mid-June in Hokkaido and in Honshu, mid-May to mid-June. Seeds do not germinate immediately after dispersal because the embryo is underdeveloped. Embryos elongated at medium temperatures in autumn after summer heat, and germination ends in No- vember at 8Њ/0ЊC. After germination, seedling emergence was delayed, and most seedlings were observed in early April around the snowmelt when soil cover was 2±3 mm.

Key words: ecophysiology; embryo elongation; Erythronium japonicum; seed germination; seedling emergence; temperature.

Erythronium japonicum Decne. (Liliaceae) (Japanese name, MATERIALS AND METHODS katakuri) is a typical vernal that inhabits the cool-tem- perate mesic deciduous-forest ¯oor. Erythronium japonicum is Seed collectionÐSeeds used in this study were collected from a natural distributed throughout Hokkaido and in broad areas from the population in a deciduous woodland in Asahikawa City, Hokkaido, Japan lowlands to the montane zone in northern and central Honshu, (43Њ52Ј N, 142Њ27Ј E). Light-brown fruits were collected in paper bags on 8 especially in the Japan Sea side of Honshu, Japan. It also oc- June 1998 and 16 June 1999 when some individuals in the population had curs sporadically on the montane zone of southwestern Hon- already dispersed seed. Collected fruits were brought to our laboratory, placed shu, Shikoku, and Kyushu in Japan. It is distributed also in in stainless steel trays, and left to dry for 1 wk. Most of the fruits had dehisced Korea, northeast China, Sakhalin, and the Kurile Islands within this time. The seeds were threshed from the dried fruit by hand, and were then winnowed, put into paper envelopes, and stored in a plastic con- (Ohwi, 1983). In Hokkaido, after the long winter with deep tainer with silica gel at 5ЊC until the start of the experiment. snow, spring is ushered in by many ¯owers immediately after the snow melts. These spring ephemerals include Adonis amu- rensis Regel et Radd, Anemone raddeana Regel, Corydalis Phenology of embryo growth in the outdoor pot experimentsÐSeeds col- lected in 1999 were used. Ten seeds were cut into thin sections with a mi- ambigua Cham. et Schl., Trillium camtschatcense Ker Gawler, crotome, and the maximum embryo length of each seed was measured under and E. japonicum. Their ¯owering and seed setting occur in a dissecting microscope equipped with a micrometer on 25 June 1999. On early spring and mid-June, respectively, and their growth ends the same day, 30 seeds were put into a ®ne-mesh polyester bag, and ®ve such in early summer. There are many popular scenic locations of bags were buried in leaf mold in a nursery ¯at at the depth of 3 cm. The ¯at these indigenous populations, including large-scale vistas of was put in a steel-framed greenhouse without vinyl or other covering at Hok- ¯owers in Japan. kaido University in Sapporo (43Њ04Ј N, 141Њ20Ј E), and the greenhouse was Erythronium japonicum has been studied in terms of its life covered with shade cloth to simulate the light conditions of a forest ¯oor. The cycle, size-class structure, resource allocation (Kawano, Hi- leaf mold was kept moist throughout the experiment. The shade cloth was ratsuka, and Hayashi, 1982), breeding and pollination systems removed, and the ¯at was kept covered with a straw mat from 15 November (Kawano and Nagai, 1982), seed dispersal (Kawano, Hiratsu- 1999 through 18 April 2000. Snow ®rst fell in mid-November and covered ka, and Hayashi, 1982; Ohkawara, Higashi, and Ohara, 1996), the ground from the end of November to the end of March. On 26 July, 25 dry-matter production, environmental requirements (Sawada et August, 23 September, 22 October, and 21 November 1999, a bag was taken al., 1997), growth and reproduction as examined by a mathe- from the mold and embryos of ten seeds were measured as above. All but matical model (Yokoi, 1976), and population structures and three of the seeds had germinated by 21 November, so on this day, only three dynamics (Yokoi, 1976; Sawada et al., 1997; Takada, Nakay- embryos were measured. The temperature of the soil surface above the bag ama, and Kawano, 1998). However, germination information was measured every 15 min with an electric thermograph throughout the needed for propagation and maintenance of population num- experiment. The daily mean, maximum, and minimum temperatures were cal- bers has not been reported. We examined the germination ecol- culated. ogy and temperature requirements for germination under both outdoors and laboratory conditions. Phenology of germination in the outdoor pot experimentsÐSeeds col- lected in 1999 were used. One hundred seeds were put in a ®ne-mesh poly- 1 Manuscript received 25 January 2002; revision accepted 16 May 2002. ester bag and three such bags were buried in leaf mold in a nursery ¯at at 4 Author for reprint requests (FAX: ϩ81-11-667-8837; e-mail: kondo@ the depth of 3 cm on 25 June 1999. The ¯at was placed in the steel-framed res.agr.hokudai.ac.jp). greenhouse and treated as in the experiment on embryo growth. 1779 1780 AMERICAN JOURNAL OF BOTANY [Vol. 89

The three bags were lifted, and seeds were examined for germination every month from June 1999 to January 2000. Here, germination is distinguished from emergence of seedlings. Germination was said to have occurred when the radicle emerged from the seed, and seedlings were said to have emerged when a cotyledon appeared above the ground. Germinated seeds were re- moved from the bags, which were buried again. In winter, the ¯at was dug out from snow for examination of germination. The maximum snow cover was about 1.5 m. The temperature of the soil surface was measured as above.

Phenology of seedling emergence in the outdoor pot experimentsÐSeeds collected in 1998 were used. Three pots 19 cm in diameter were ®lled with a 1 : 1 mixture of peat moss and vermiculite. One hundred seeds were sown in each pot and covered with 2±3 mm of sieved soil on 16 June 1998. The pots were covered with shade cloth to prevent dryness and protect against insects and placed in the greenhouse. The soil was kept moist throughout the experiment. The shade cloth was removed and the pots were covered with a straw mat from 16 October 1998 until 19 April 1999. Pots were examined monthly for seedlings that had emerged, and emerged seedlings were removed from the pots. The maximum snow cover was about 1.5 m. The temperature of the soil surface was measured as above. Fig. 1. Temperatures in the ®eld and mean lengths (Ϯ1 SD) of embryos of Erythronium japonicum. Lengths of ten embryos were measured on 25 June, and on the same day, 150 seeds were buried in leaf mold. On 26 July, Effects of constant or alternating temperatures on germinationÐSeeds 25 August, 23 September, and 22 October, the seeds were unburied, ten were collected in 1999 were treated with 500 ppm (parts per million) of benomyl chosen at random, and lengths of embryos were measured. On 21 November, for 24 h for bacterial control before being used in this experiment. On 24 only three embryos could be measured; all other seeds had germinated. June 1999, the experiment was started in a temperature- and light-controlled incubator with a 12-h photoperiod with seeds in 9-cm glass petri dishes on a double layer of ®lter paper moistened with distilled water. Five constant tem- perature treatment was effective for the germination. Seeds were placed at peratures (0Њ,5Њ,10Њ,15Њ, and 20ЊC) and two regimes of alternating temper- 25Њ/15ЊC for 30 d, 60 d, 90 d, or 120 d and then moved to 5ЊC. atures with 12 h at each temperature (15Њ/5Њ and 20Њ/10ЊC, light 12 h/dark 12 h) were used. At constant temperatures, seeds were exposed to light for 12 h Effects of temperature on embryo growthÐIn an examination of the ef- each day; and at 12/12 h alternating temperatures, seeds were in light during fects of temperature on embryo growth, seeds were kept at 0Њ,5Њ,or25Њ/15ЊC the high-temperature period and in the dark during the low-temperature pe- throughout the experiment, or else at 25Њ/15ЊC for 90 d before being moved riod. The light source was 40-W white ¯uorescent tubes, and the irradiance to 5ЊC. The lengths of ten embryos were measured on 25 June, 25 July, 25 at the level of the seeds was about 20 ␮mol´mϪ2 ´sϪ1 on a double layer of August, 23 September, 22 October, 21 November, and 21 December as in the ®lter paper moistened with distilled water. Four concurrent trials of 30 seeds experiment on the phenology of embryo growth in the outdoors. were used for each set of conditions. Observations were made at 1 or 2 d, and germinated seeds were counted and removed. The ®lter paper was re- RESULTS moistened with distilled water regularly. Phenology of embryo growth in the outdoor pot experi- mentsÐThe mean maximum and minimum temperatures were Germination at temperatures simulating outdoors conditionsÐSeeds were 32Њ/17ЊC from 25 June to 15 September and 14Њ/6ЊC from 16 placed at 25Њ/15ЊC for 90 d, moved to 15Њ/5ЊC for 60 d, and moved to 5ЊC September to 30 November 1999 (Fig. 1). The mean embryo in a simulation of outdoor temperatures. Temperatures of 25Њ/15Њ,15Њ/5Њ, and length of fresh seeds on 25 June was 0.33 Ϯ 0.04 mm, which 5ЊC corresponded roughly to the maximum and minimum temperatures in the outdoors from mid-June to mid-September, from mid-September to the be- was 8.1% of mean seed length (4.09 Ϯ 0.35 mm). Embryos ginning of November, and from the beginning of November to the end of grew little until they started slow growth in August. From the December, respectively. The date of seed collection, control of bacteria, the beginning of September, when temperatures were medium or number of seeds, the method of sowing, light conditions, and observations low, embryos grew rapidly and reached a mean of 3.23 mm were the same here and in the experiments below as in the experiment above on 21 November, by which time 93% of seeds had germinated. on temperature. The large SD for embryo length on 21 November was partly accounted for by the small number of embryos left to be mea- .Effects of high temperatures (25؇/15؇C) before germination at various low sured temperaturesÐIn an experiment examining the effects of high-temperature treatment on germination at four low temperatures, we kept seeds at 25Њ/15ЊC Phenology of germination in the outdoor pot experi- for 90 d and then moved them to 0Њ,5Њ,10Њ,or15ЊC. At 0ЊC, seeds were mentsÐSeeds sown on 25 June 1999 did not germinate im- kept in the dark continuously because of the incubator's limited capacity. mediately. After the high temperatures of summer and medium Germination at various low temperatures was observed as in the above ex- temperatures of autumn, germination was ®rst detected on 5 periment. November (Fig. 2). Many remaining seeds germinated rapidly within November, with minimum and maximum temperatures .Effects of various temperatures before germination at 5؇CÐIn an exper- of 8Њ/0ЊC, and 86% of seeds had germinated by 3 December iment done to identify the optimum temperature before germination, seeds were kept at 25Њ/15Њ,20Њ,25Њ,or30ЊC for 90 d and then moved to 5ЊC. Phenology of seedling emergence in the outdoor pot ex- Germination was observed as in the above experiments. perimentsÐThe mean maximum and minimum temperatures were 24Њ and 16ЊC from 16 June 1998 to 15 September, 14Њ/ Effects of length of high-temperature treatment before germination at 6ЊC (maximum/minimum) from 16 September to 30 Novem- 5؇CÐIn this experiment, we examined which of four periods of high-tem- ber, 0Њ/0ЊC from 1 December to 5 April, and 10Њ/1ЊC from 6 November 2002] KONDO ET AL.ÐECOPHYSIOLOGY OF SEED GERMINATION IN E. JAPONICUM 1781

Fig. 4. Effects of constant or alternating temperatures on germination. Seeds were incubated at ®ve constant temperatures (0Њ,5Њ,10Њ,15Њ, and 20ЊC) and two regimens of alternating temperatures with 12 h at each temperature Fig. 2. Temperatures in the ®eld and mean percentage of seeds that ger- (15Њ/5ЊC and 20Њ/10ЊC). At constant temperatures, seeds were exposed to light minated (Ϯ1 SD). Three lots of 100 seeds were buried in leaf mold, and for 12 h each day; and at 12/12 h alternating temperatures, seeds were in light germinated seeds were counted monthly and removed. during the high-temperature period and in the dark during the low-temperature period. Conditions that did not lead to germination are not included in the ®gure. Four lots of 30 seeds were treated at each temperature or pair of temperatures. Observations were made daily or every other day, but datum to 22 April (Fig. 3). Seedlings emerged a considerable time points are for results obtained every ®fth day. after germinating, although the soil cover was thin. Cotyledons of seeds sown on 16 June 1998 began to emerge on 1 Decem- ber 1999 under the snow; the temperature was 0ЊC at the time Germination at temperatures simulating outdoors condi- of the observation. More seedlings emerged under the snow, tionsÐSeeds did not germinate during the 90-d incubation at and we observed cotyledons surviving even when enclosed in alternating temperatures of 25Њ/15ЊC (light 12 h/dark 12 h) ice. On 16 March 1999, 28% of the seedlings were about 1± (Fig. 5). However, 45 d after being moved to 15Њ/5ЊC, seeds 4 cm long. Seedling emergence was 82% on 15 April, 1 wk began to germinate, and germination was 100% after 30 d at after snowmelt ended. By 22 April, 86% of seeds had 5ЊC. The results of this experiment and the preceding one sug- emerged. gested that high (25Њ/15ЊC) and medium (15Њ/5ЊC) tempera- tures promoted the germination of E. japonicum seeds moved Effects of constant or alternating temperatures on germi- to a low temperature later. nationÐOf the various conditions tried, a continuous temper- -ature of 10ЊC and alternating temperatures of 15Њ/5ЊC (light Effects of high temperatures (25؇/15؇C) before germina 12 h/dark 12 h) led to seed germination, which was seen ®rst tion at various low temperaturesÐSeeds did not germinate 130 d after sowing (Fig. 4). At 200 d, germination at 10Њ and within 90 d at the high temperatures of 25Њ/15ЊC, as before, 15Њ/5ЊC reached 84% and 74%, respectively. but 40 d after being moved to 0Њ,5Њ,or10ЊC, they began to germinate, with 88%, 92%, and 99% germination, respective-

Fig. 5. Germination at temperatures simulating ®eld conditions. Seeds Fig. 3. Temperatures in the ®eld and mean percentage of seedlings that were incubated with 12 h of light and 12 h of dark at 25Њ/15ЊC for 90 d and emerged (Ϯ1 SD). Three lots of 100 seeds were sown on soil (a 1 : 1 mixture then moved to 15Њ/5ЊC for 60 d before being placed at 5ЊC in a simulation of peat moss and vermiculite) and covered with 2±3 mm of sieved soil. Seed- of ®eld temperatures from mid-June to the end of December. Four lots of 30 lings that appeared above the soil surface were counted and removed monthly. seeds were used. Observations were as in Fig. 4. 1782 AMERICAN JOURNAL OF BOTANY [Vol. 89

Fig. 6. Effects of high temperatures (25Њ/15ЊC) before germination at var- Fig. 8. Effects of length of high-temperature treatment before germination ious low temperatures. After the high temperatures for 90 d, seeds were at 5ЊC. Seeds were placed at 25Њ/15ЊC for 30 d, 60 d, 90 d, or 120 d and moved to 0Њ,5Њ,10Њ,or15ЊC. Four lots of 30 seeds were used for each set moved to 5ЊC. Four lots of 30 seeds were used for each set of conditions. of conditions. Observations were as in the legend of Fig. 4. Observations were as in the legend of Fig. 4. ly, by 200 d after sowing (Fig. 6). These ®nal germination bated at 5ЊC after the high temperatures for 30 d, 60 d, 90 d, percentages were not signi®cantly different at the three tem- or 120 d, the germination started at 90 d, 60 d, 48 d, or 41 d, peratures (SheffeÂ's test, P Ͻ 0.05 level). Seeds did not ger- respectively, after the move to 5ЊC. minate when kept at 25Њ/15ЊC for 90 d and then at 15ЊC for 110 d. Effects of temperature on embryo growthÐEmbryos of seeds kept at 0Њ,5Њ,25Њ/15Њ,or25Њ/15ЊC for 90 d followed by Effects of various high temperatures before germination 5ЊC were seen to grow little until they were measured on 25 at 5؇CÐThe high temperature of 25Њ/15Њ or 20ЊC for 90 d August, 63 d after incubation (Fig. 9). Embryos kept at 0Њ or allowed later germination at 5ЊC, and germination exceeded 5ЊC did not grow at any time. Embryos placed at 25Њ/15ЊC 90% (Fig. 7). The high temperature of 25Њ or 30ЊC also al- grew, but their ®nal mean length was 1.6 mm, about half that lowed later germination at 5ЊC, but germination was Ͻ30%. after 25Њ/15ЊC for 90 d followed by 5ЊC, and the seeds had not germinated by the end of the experiment. However, em- Effects of length of high-temperature treatment before bryos kept at 25Њ/15ЊC for 90 d followed by 5ЊC grew rapidly germination at 5؇CÐHigh temperatures of 25Њ/15ЊC for 30 d, after day 63, and 95% of the seeds had germinated by day 60 d, 90 d, or 120 d followed by incubation at 5ЊC gave ®nal 180 (21 December). The course of embryo growth at 25Њ/15ЊC germination percentages of 84%, 93%, 92%, and 94%, re- for 90 d followed by 5ЊC was similar to that in the outdoors. spectively (Fig. 8). In other words, 30 d at the high tempera- ture was long enough to allow germination later at a low tem- DISCUSSION perature. The days to germination after sowing were greater Germination and seedling phenologyÐEmbryos in freshly with longer periods of high temperature. However, the days to matured seeds of E. japonicum were a mean of 0.33 mm long, germination after seeds were moved to 5ЊC were fewer with much less than the mean length of the seeds, 4.09 mm. Em- longer periods of high temperature. When seeds were incu-

Fig. 9. Effects of temperature on embryo growth. Seeds were kept at 0Њ, Fig. 7. Effects of various high temperatures before germination at 5ЊC. 5Њ,or25Њ/15ЊC throughout the experiment or else at 25Њ/15 ЊC for 90 d before Seeds were placed at 25Њ/15Њ,20Њ,25Њ,or30ЊC for 90 d and moved to 5ЊC. being moved to 5ЊC. The mean lengths (Ϯ1 SD) of ten embryos measured Four lots of 30 seeds were used for each set of conditions. Observations were on 25 June, 26 July, 25 August, 23 September, 22 October, 21 November, as in Fig. 4. and 21 December are shown. November 2002] KONDO ET AL.ÐECOPHYSIOLOGY OF SEED GERMINATION IN E. JAPONICUM 1783 bryos of freshly matured seeds of E. albidum (Baskin and japonicum, if seeds were kept at high temperatures ®rst, the Baskin, 1985a), E. grandi¯orum (Baskin, Meyer, and Baskin, germination temperature widened to the low temperatures of 1995), E. americanum, and E. rostratum (Baskin and Baskin, 0Њ,5Њ, and 10ЊC. Therefore, an initial period of high temper- 1998) also are small. atures may be one factor that breaks dormancy; this would be Seeds of E. japonicum are dispersed in mid-June in Hok- consistent with the ®nding in the outdoor experiment that kaido, but embryos did not elongate in the high temperatures seeds germinated in November at 8Њ/0ЊC after the summer. A of summer. Embryos grew rapidly from September to Novem- review of papers reporting germination of seeds of in ber as the temperature decreased at 14Њ/6ЊC. After the embryos the genus Erythronium (Griswold, 1936; Pelton, 1956; Muller, had elongated enough, germination started at once (in early 1978; Kawano, Hiratsuka, and Hayashi, 1982; Baskin and November); in 1999, 86% had germinated between 5 Novem- Baskin, 1985a; Baskin, Meyer, and Baskin, 1995) did not re- ber and 3 December at 8Њ/0ЊC. veal any report that initial high temperatures widens the tem- Embryos of E. albidum also were initially underdeveloped; perature range for germination. Of the temperatures we tried, embryos began to elongate in September, and the elongation the most effective high temperatures for germination were 20Њ was greatest in October and November when they were placed or 25Њ/15ЊC. After such high temperatures, the temperature for in a garden. However, such embryos continue to elongate dur- germination was widened to 0Њ±10ЊC. ing the winter, and germination (de®ned as we did here) was However, seeds of E. albidum germinated to high percent- ®rst detected on 15 February 1984 (Baskin and Baskin, ages at 15Њ/6ЊC following 12 wk at 30Њ/15ЊC along with 12 1985a). Also in the nonheated greenhouse experiments, seeds wk at 5ЊC (Baskin and Baskin, 1985a). germinated in the period from 21 to 28 February 1983 at 14Њ/ We can explain the germination phenology of E. japonicum 4ЊC; 90% had germinated by the period from 7 to 14 March in the outdoors by temperature requirements of seeds from our 1983 at 14Њ/4ЊC; and 24% had also germinated in the period results. In the outdoors, seeds are dispersed in mid-June in from 14 to 20 February 1984 when at 19Њ/7ЊC (Baskin and Hokkaido, Japan, without germinating immediately. Their em- Baskin, 1985a). bryos are underdeveloped when seeds are dispersed. High tem- To summarize our results and theirs, embryo elongation and peratures followed by medium or low temperatures are needed germination of E. japonicum is brought to completion at low to elongate their embryos. Germination occurs at low temper- temperatures within the year after the high temperature of the atures after the full elongation of embryo. Therefore, seeds do summer, although embryo elongation of E. albidum continues not germinate immediately after their dispersal, and seeds ger- during the winter and germination starts in late winter at me- minate in late autumn after summer heat. After germination, dium temperatures. seedling emergence is delayed under the snow, and most seed- The outdoor temperatures until November in their experi- lings are observed in early April around the snowmelt. ments and ours were similar, but the temperatures during the winter differed greatly. In winter, E. japonicum was grown in LITERATURE CITED Sapporo, Hokkaido at a fairly constant 0ЊC because of the snow cover. Erythronium albidum was grown in Lexington, Kentucky, USA, where the temperature from December to BASKIN,C.C.,AND J. M. BASKIN. 1998. Seeds: ecology, biogeography, and evolution of dormancy and germination. Academic Press, New York, February is very low, sometimes as low as Ϫ20ЊC (Baskin New York, USA. and Baskin, 1985a). The results from their outdoor experi- BASKIN,J.M.,AND C. C. BASKIN. 1985a. Seed germination ecophysiology ments might mean that the severe winter delayed the germi- of the woodland spring geophyte Erythronium albidum. Botanical Ga- nation of E. albidum. However, as described in the following zette 146: 130±136. section, our laboratory experiments showed that the different BASKIN,J.M.,AND C. C. BASKIN. 1985b. The annual dormancy cycle in germination phenology of the two species arose from their buried weed seeds: a continuum. Bioscience 35: 492±498. BASKIN, C. C., S. E. MEYER, AND J. M. BASKIN. 1995. Two types of mor- different temperature responses not from the different temper- phophysiological dormancy in seeds of two genera (Osmorhiza and Er- atures in the outdoor experiments. ythronium) with an Arcto-Tertiary distribution pattern. American Journal We found that germination of E. japonicum in the strict of Botany 82: 293±298. sense had already ended within November, that about 30% of GRISWOLD, S. M. 1936. Effect of alternate moistening and drying on ger- the cotyledons emerged under the snow, and that most coty- mination of seeds of western range plants. Botanical Gazette 98: 243± ledons had emerged by early April around snowmelt. Many 269. KAWANO, S., A. HIRATSUKA, AND K. HAYASHI. 1982. Life history charac- plants whose cotyledons do not emerge immediately after rad- teristics and survivorship of Erythronium japonicum: the productive and icle emergence are known. This phenomenon is referred to as reproductive biology of ¯owering plants, V. Oikos 38: 129±149. ``epicotyl dormancy'' (Baskin and Baskin, 1998). Erythronium KAWANO, S., AND Y. N AGAI. 1982. Further observations on the reproductive japonicum also seems to have epicotyl dormancy. biology of Erythronium japonicum (L.) DECNE. (Liliaceae). Journal of Phytogeography and Taxonomy 30: 90±97. Effects of temperature on embryo elongation and germi- KONDO, T. 1993. Germination characteristics of wild¯ower. Journal of the Japanese Institute of Landscape Architects 57: 121±128 (in Japanese nationÐEmbryos of E. japonicum did not grow well when with English summary). kept at only the high temperatures of 25Њ/15ЊC or only the low KONDO, T., H. MAENAKA, AND R. TAKAHASHI. 1992. Propagation and veg- temperatures of 0Њ or 5ЊC. Embryos grew rapidly and seeds etational management of wild ¯owers: germination, cutting propagation, germinated when kept at 25Њ/15ЊC for 90 d and then at 5ЊC. and frequency and timing of mowing for extending the ¯owering season However, embryos could elongate at temperatures near 10ЊC, of Aster ageratoides subsp. ovatus Kitam. Journal of the Japanese So- because seeds placed at 10Њ or 15Њ/5ЊC germinated but seeds ciety of Revegetation Technology 17: 193±202 (in Japanese with English placed at 0Њ,5Њ,15Њ,20Њ or 20Њ/10ЊC did not germinate. summary). MULLER, R. N. 1978. The phenology, growth and ecosystem dynamics of In many species, the temperature range for germination wid- Erythronium americanum in the northern hardwood forest. Ecological ens after dormancy is broken (Baskin and Baskin, 1985b; Kon- Monographs 48: 1±20. do, Maenaka, and Takahashi, 1992; Kondo, 1993). With E. OHKAWARA, K., S. HIGASHI, AND M. OHARA. 1996. Effects of ants, ground 1784 AMERICAN JOURNAL OF BOTANY [Vol. 89

beetles and the seed-fall patterns on myrmecochory of Erythronium ja- differing in sunlight exposure in cool temperate Japan. Ecological Re- ponicum Decne. (Liliaceae). Oecologia 106: 500±506. search 12: 89±99. OHWI, J. 1983. New ¯ora of Japan. Shibundo, Tokyo (in Japanese). TAKADA, T., S. NAKAYAMA, AND S. KAWANO. 1998. A sensitivity analysis PELTON, J. 1956. A study of seed dormancy in eighteen species of high of the population dynamics of Erythronium japonicum, a liliaceous pe- altitude Colorado plants. Butler University Botanical Studies 13: 74±84. rennial. Plant Species Biology 13: 117±127. SAWADA, S., S. CHIBA,Y.SAWAGUCHI, AND N. NAGASAWA. 1997. Dry mat- YOKOI, Y. 1976. Growth and reproduction in higher plants. II. Analytical ter production, population structure and environmental conditions of the study of growth and reproduction of Erythronium japonicum. Botanical spring ephemeral Erythronium japonicum growing in various habitats Magazine Tokyo 89: 15±31.