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Theresa L. Bosma, Janet C. Cole, Kenneth E. Conway, and John M. Dole

Canterbury bells (Campanula medium `Champion Blue') seeds were primed using calcined clay at 68 °F (20 °C) for 1, 3, or 5 days at water potentials (Ψ) of -25, -20, -18, or -16 bars (-2.5, -2.0, -1.8, or -1.6 MPa). Germination was fastest (3.0 to 3.1 days) after priming with a Ψ of -18 or -16 bars for 5 days. Seeds primed for 3 or 5 days with moisture present germinated faster than nonprimed seeds, but time to 50% germination (T50) was longer when seeds were primed for 1 day regardless of Ψ compared to nonprimed seed. Germination uniformity decreased (time from 10% to 90% germination, T10-90, increased) as Ψ increased. Although a curvilinear relationship existed between T10-90 and priming duration, T10-90 did not differ between nonprimed seeds and seeds in any priming treatment except those primed for 3 days with 20% moisture (-16 bars). Priming did not affect total germination percentage (97%).

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James W. Frisby and Schuyler D. Seeley

We compared peach [Prunus persica (L.) Batsch cv. Johnson Elberta] seed germination (G) and seedling emergence (E) after various stratification (St) treatments. Treatments were arranged in factorial combinations of five St durations (20 to 60 days) at eight constant temperatures (0 to 18C) in a completely randomized design followed by repeated measures during forcing time. G and E were recorded every 5 days during forcing. Seed St at 0 to 10C and 0 to 14C promoted G and E, respectively. G and E increased with longer St treatments at promoting temperatures. There was a weak correlation between G and E averaged over the forcing measurements (r 2 = 0.54). The best correlation was between E after 15 days and G after 10 days (r 2 = 0.83). The results indicate that G and E in peach are not identical indicators of endodormancy (ED) release and should not be used interchangeably. Forcing times must be considered when making comparisons between G and E.

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Ekaterina A. Jeliazkova, Valtcho D. Jeliazkov, Lyle E. Craker, and Baoshan Xing

Phytoremediation has been suggested as a solution to heavy metal—polluted soils, but the choices of suitable plant species for phytoremediation have been limited. Medicinal and aromatic plants appear to be excellent selections for these plantings, since these plants are grown for economically valuable secondary products (essential oils), not for food or feed. Preliminary research indicates that heavy metals are not accumulated in essential oils, permitting the oil to be used commercially. Productivity of some, but not all aromatic plants was reduced, however, by the heavy metals. The objective of our experiment was to distinguish the mechanism of heavy metal tolerance of plants using germinating seeds of medicinal and aromatic plant species. Seeds from medicinal and aromatic plants were germinated in solutions with selected levels of heavy metals (cadmium at 6 and 10 (μg·L-1; copper at 60 and 150 μg·L-1; lead at 100 and 500 μg·L-1; zinc at 400 and 800 μg·L-1) and in distilled water. Tests on Anethum graveolens L., Carum carvi L., Cuminum cyminum L., Foeniculum vulgare Mill., Pimpinella anisum L., Ocimum basilicum L., and the hyperaccumulator species Brassica juncea L. and Alyssum bertolonii established that different plant species reacted in different ways to the heavy metals. For example, cadmium did not decrease seed germination of Alyssum, O. basilicum, and B. juncea compared with germination in water but did decrease germination of C. cyminum. Lead did not affect germination of A. bertolonii and B. juncea as compared with water but did negatively affect germination of P. anisum, F. vulgare, and C. cyminum. Except for B. juncea, F. vulgare, and C. cyminum, copper had a negative effect on germination. Zinc decreased germination in all tested species except B. juncea.

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J. Ryan Stewart and William R. Graves

Little is known about the reproductive biology of carolina buckthorn [Rhamnus caroliniana Walt. or Frangula caroliniana (Walt.) Gray], an attractive North American shrub or small tree that might merit increased use in managed landscapes. The fecundity and high germinability of seeds of the Eurasian common buckthorn (Rhamnus cathartica L.), however, have been characterized as factors contributing to its invasiveness. We compared seed germination of these species to ascertain how easily carolina buckthorn could be grown from seed in nurseries and to acquire data for predicting whether carolina buckthorn might be invasive if introduced into managed landscapes. Fruits of carolina buckthorn were collected from indigenous plants in central Missouri, southern Oklahoma, and southern Texas. Fruits of common buckthorn were collected from shrubs naturalized in central Iowa. Seeds of both species were stratified for up to 112 days in darkness at 4 °C; germination at 24 °C in the dark was then evaluated for 56 days. Quadratic functions best described how time of stratification influenced germination value and germination percentage of common buckthorn, whereas these measures of carolina buckthorn were best represented by exponential (value) or linear (percentage) functions. Stratification for 112 days maximized germination value and percentage for carolina buckthorn within the 56-day germination period, but shorter stratifications were sufficient to optimize germination of common buckthorn. While the overall mean germination of carolina buckthorn was 40%, results varied by provenance and ranged from 25% (Missouri) to 56% (Oklahoma). Mean germination of common buckthorn over times of stratification was 71%, and the overall mean daily germination of common buckthorn, 1.3, was 86% greater than that of carolina buckthorn, 0.7. We conclude that seeds of carolina buckthorn are more resistant to germination than seeds of common buckthorn. Our results suggest that plant propagators should cold-stratify seeds of carolina buckthorn for up to 112 days, and suggest that carolina buckthorn has a lower potential to be invasive than does common buckthorn.

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Frank Balestri and William R. Graves

gum can germinate with pulp of drupes intact, although it is unknown whether pulp enhances or impedes seed germination of Nyssa spp. Fagan et al. (1981) demonstrated that seeds of lily turf [ Liriope muscari (Decne.) L.H. Bailey] with their mealy

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Ali O. Sari, Mario R. Morales, and James E. Simon

Echinacea pallida, one of the three medicinal Echinacea species native to North America, is generally wildcrafted, and low and uneven seed germination are obstacles to its widespread cultivation. Nonstratified E. pallida seeds were treated with 2500, 3500, and 4500 mg/L GA3 to increase seed germination. Treated seeds were directly germinated at 25 °C and 25/15 °C (14/10h) or stored at 5 and 10 °C for 4, 8, and 12 weeks before germination at the same temperatures. Seed germination across treatments was higher at 25 °C (19%) than at 25/15 °C (14%). Application of 2500, 3500, and 4500 mg/L GA3 significantly increased seed germination rate and total seed germination of nonstratified seeds of E. pallida and resulted in 44%, 50%, and 63% total seed germination, respectively, while untreated control seeds germinated at only 9%. The effect of GA3 as a germination stimulant increased with cold storage, with maximum germination (83%) occurring after seeds were treated with 4500 mg/L GA3 and an 8-week cold storage period at 10 °C. The effect of cold storage periods of 4, 8, and 12 weeks and cold storage temperatures of 5 and 10 °C on seed germination were generally similar. Seeds collected from the upper rows of the seed heads germinated significantly higher (10.6%) than those collected from the lowest seed rows (2.4%).

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Kit L. Chin, Catalino A. Blanche, and V.R. Bachireddy

Rapid and timely production of kiwi (Actinidia deliciosa) seedlings is often hampered by poor and erratic seed germination. This investigation was conducted to assess the effect of gibberellic acid, cold stratification (5° C), and their combinations on seed germination and subsequent radicle elongation. Germination counts and radicle elongation measurements were made two weeks after incubation at 25.4° C under continuous light and approximately 100% RH. GA treatments broke dormancy and increased germination and radicle elongation with increasing concentration up to 2500 ppm. At 5000 ppm, germination and radicle elongation were reduced. Cold stratification (1 and 2 week durations) alone did not affect germination nor break dormancy. Combined cold stratification and GA treatments significantly enhanced seed germination and radicle elongation with the best response at the highest GA concentration (5000 ppm) and longest stratification (2 weeks), regardless of whether the seeds were stratified prior to or after GA treatments.

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Han Huang and M. Yamaguchi

Abstract

Tomato seeds were more responsive than wheat or lettuce seeds to the presence of an inhibitor in the juice of tomato fruits. Seed germination and seedling growth decreased with increasing concentrations of juice. Inhibition of seed germination in 20% juice with an osmotic concentration of less than 0.1 M was significantly less than in 0.1 M glucose or mannitol with 0.01 M citric acid at pH 4.4. The inhibitor in tomato juice was thermostable, but the effect decreased with prolonged storage at -20°C. There were cultivar differences in the amount of inhibitor present in ripe tomato fruits.

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Terry L. Gilbertson-Ferriss and H. F. Wilkins

Abstract

Seed germination of ‘Royal Mix’ freesia was most rapid and uniform at 15.5° or 18.5°C under clear polyethylene or at 13° or 21.5°C under black polyethylene. Soaking seeds in running water prior to germination or removal of the seed coat did not improve seed germination

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Yung-I Lee, Nean Lee, Edward C. Yeung, and Mei-Chu Chung

This investigation documents the key anatomical features in embryo development of Cypripedium formosanum Hayata, in association with the ability of embryos to germinate in vitro, and examines the effects of culture media and seed pretreatments on seed germination. A better understanding of zygotic embryogenesis for the Cypripedium L. species would provide insights into subsequent germination events and aid in the in vitro propagation of these endangered species. In seeds collected at 60 days after pollination (DAP), soon after fertilization, no germination was recorded. The best overall germination was found at 90 DAP (≈70%), at which time early globular to globular embryos with a single-celled suspensors can be observed. After 135 DAP, the seeds germinated poorly. At this time the inner integument shrinks and forms a tight layer, which encloses the embryo, the so-called “carapace.” Using Nile red stain, a cuticular substance was detected in the carapace, which may play a role in the impermeability of the mature seed and may help the seeds survive in the stringent environment. At maturity (after 210 DAP), the embryo proper has an average size of eight cells along its length and six cells across the width. Lipids and proteins are the main storage products within the embryo. To improve seed germination, experiments were conducted to test the suitability of various media and pretreatments of seeds. When different media were used, except for the Harvais medium at 120 DAP, there was no significant difference in seed germination at three different developmental stages tested. Soaking mature seeds in 1% NaOCl or treating them with ultrasound may slightly increase the germination percentage. For seed germination, our results indicate that the timing of seed collection outweighs the composition of medium and the seed pretreatments.