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Sandra A. Balch, Cynthia B. McKenney and Dick L. Auld

Oenothera biennis, common evening primrose, is grown commercially for its seed, which contains high levels of gamma-linolenic acid (GLA), a fatty acid with pharmaceutical and dietary importance. Other native species of Oenothera are being evaluated for the presence of GLA in their seed and their potential as a commercial source of GLA. Native evening primrose species have shown slow emergence and low germination percentages. Studies were conducted to determine the effects of chilling, scarification, and priming on germination of seed for six species of native evening primrose. Overall, seed germination was improved by seed treatments. However, responses to the various treatments differed among species.

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Alireza Talaie* and Rasoul Akrami

The objective of this study was the identification of existing olive trees in eight regions of Kermanshah province and investigation of their fruit, seed, and leaf characteristics in order to be used in the olive production industry of Iran. The germination ability of olive seed in field and nursery were also studied. In this research, 61 genotypes were identified and their characteristics were studied. It was found out that the present genotypes of Kermanshah showed different vegetative and reproductive growth based on the climatic and topographic conditions. This was verified by cluster analysis of the genotypes of different regions, which showed clearly their far and close relations. It was found out that some of the genotypes in the region spite of their appearance differences have same origin and most probably should be considered as the same genotype. The results also showed that favorable seed bed, planting depth and scarification of the seeds have positive effects on their germination while scarification of the seeds without other treatments had no significant effect on the seed germination.

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Jimmy L. Tipton

The maximum predicted germination was 95% after 62 minutes scarification and 35 days stratification for mexican redbud (Cercis canadensis var. mexicana) and 59% after 52 minutes scarification and 73 days stratification for evergreen sumac (Rhus virens). Mexican redbud germination occurred from 24 to 31 C, evergreen sumac from 21 to 31 C, and mealy sage (Salvia farinacea) from 21 to 34 C. The maximum predicted final percent germination and the temperature at which it occurred for mexican redbud, evergreen sumac, and mealy sage was 104 at 27 C, 90 at 29 C, and 42 at 22 C, respectively. The maximum predicted maximum germination rate and the temperature at which it occurred for mexican redbud, evergreen sumac, and mealy sage was 30 at 31 C, 69 at 31 C, and 104 at 27 C, respectively. The minimum predicted inflection time and the temperature at which it occurred for mexican redbud, evergreen sumac, and mealy sage was 4 days at 28 C, 10 days at 25 C, and 3 days at 28 C, respectively.

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William J. Carpenter, Eric R. Ostmark and John A. Cornell

High synchrony, rate, and germination of needle palm [Rhapidophyllum hystrix (Pursh) H.A. Wendle & Drude] seeds were achieved only after removing the sclerotesta and embryo cap, which imposed physical dormancy. After scarification, recently harvested seeds or seeds stored for 12 months at 5C and 100% relative humidity had 96% and 98% final germination (G), with 9 to 11 days required to achieve 50% of final germination (T50) at 30C. Germination temperature controlled G, T50, and days between 10% and 90% of final germination (T90 - T10) of scarified seeds, with respective values of 98%) 9 days, and 5 days at 30C, and 18%, 31 days, and 12 days at 15C. Seeds with 36% moisture at harvest had no reduction in G until moisture was <14%. Germination of seeds with 19% moisture declined from 80% if stored at 0C to 33% if stored at -l0C; no seeds germinated after storage at less than -l0C.

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Derek N. Peacock and Kim E. Hummer

Many Rubus species have a seedcoat imposed exogenous dormancy. Our objective was to contrast the effect of liquid nitrogen (LN2), sulfuric acid (H2SO4), and an untreated control on seed germination of R. multibracteatus A. Leveille & Vaniot and R. parviflorus Nutt. and to determine if LN2 could be used as a mechanical scarifying agent for these species. Three replicates of 100 seeds of each species were treated with either three 3-min dips in LN2 with corresponding 10 min thaws or for 30 min with H2SO4 or were left untreated. The LN2 pretreatment did not significantly reduce the viability of R. multibracteatus or R. parviflorus as compared to the control. A random sample of germinated R. multibracteatus from the LN2 pretreatment showed normal seedling development upon planting. The H2SO4 pretreatment significantly increased germination percentages as compared to the control or LN2 pretreatment as well as for R. ursinus Cham. & Schldl. and R. eustephanus Focke ex Diels. The LN2 treatment did not significantly improve germination over the control group and therefore was not an effective scarifying agent as applied to R. multibracteatus or R. parviflorus. However, these two Rubus species were not damaged by repeated dips in LN2. Alternative LN2 pretreatments are being examined for their potential to improve Rubus germination further.

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Gary R. Bachman and Ted Whitwell

Southern seaoats (Uniola particulata) are difficult to propagate from seed due to low seed numbers produced and cold dormancy effects. To efficiently produce southern seaoats in the nursery industry the dormancy must be effectively broken to assure quick and even germination. 24 hr soaks in gibberillic acid (100 and 500 ppm) or scarification of the seed coat combined with GA soaks were compared. Seeds were planted in 50/50 peat/perlite medium 2.5 cm deep. 21 DAT both the 100 and 500 ppm GA soaks had higher germination rates. The 100 ppm GA was determined to he most effective (56% germination) with the seedlings being 3 cm in length. The 500 ppm treated seeds were 6 cm in length hut twisted from the GA causing excessive cell elongation.

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Wayne A. Mackay and Tim D. Davis

Seeds of four lupine species (L. microcarpus var. aureus, L. havardii, L. succulentis, and L. texensis) were subjected to 0, –2, –4, –6, or –8 bars osmotic potential using PEG 8000 solutions. Seeds of all species were acid scarified prior to placement in petri dishes containing the osmotic solutions. Petri dishes were placed in a seed germination chamber at 25°C with germination data collected daily for 15 days. Seeds of L. havardii, a desert species native to west Texas exhibited the greatest germination as osmotic potential declined while L. succulentis, a species adapted to moist sites, exhibited the greatest decline in germination as osmotic potential decreased. The other species exhibited intermediate germinability under the lower osmotic potentials.

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Christia M. Roberts

Lewisia tweedyi (A. Gray) Robinson is an endangered, herbaceous perennial native to the Cascade Mountains of northern Washington state and southern British Columbia. It is highly valued as an ornamental, but has a reputation for being challenging to grow and is only cultivated by alpine specialists. The better known Lewisia species, L. cotyledon, is a minor commercial crop in some areas of Europe and western North America. Lewisias are members of the Centrospermae; a linear peripheral embryo surrounds centrally located perisperm. Lewisia tweedyi seed is distinct from all other lewisias in having a fleshy appendage, or caruncle. Germination practices include stratification for an unspecified period in a garden cold frame. In addition to a long germination period, percent germination is characteristically low. A number of tests, including sowing under axenic conditions, and combinations of prechill periods and liquid N scarification were conducted. Seedcoat-imposed dormancy and germination requirements have been determined.

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Gary A. Couvillon

Several studies with annual crops have shown that large seeds improve percent germination, seedling growth, and uniformity, yield, seedling vigor, and stress tolerance. Little information is available on the influence of seed size on the resulting seedlings of woody plant species. Cercis canadensis L. seeds were divided into large and small seed size fractions and the seeds scarified, stratified, and planted. A larger percentage of large seeds germinated than did small seeds. Seedlings from large seeds had a greater peak and germination value than small seeds, indicating greater vigor and a more rapid germination rate thus more uniform seedlings. Seedlings from large seeds, as indicated by fresh and dry weights, were larger and contained a greater leaf area than those produced by small seed.

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Robert L. Geneve

Seed dormancy in Eastern redbud (Cercis canadensis var. canadensis L.) can be overcome by seedcoat scarification to allow water imbibition, followed by chilling stratification to permit germination. During chilling stratification, there was an increase in the growth potential of the embryo as indicated by the ability of the isolated embryo to germinate in osmotic solutions. Penetration resistance of the testa also decreased after chilling stratification. The combination of seedcoat alteration and the increase in embryonic growth potential was associated with overcoming dormancy in redbud seed. GA3 or ethephon (50 μm) stimulated germination (28% and 60%, respectively) and increased the growth potential of treated embryos. Chemical names used: gibberellic acid (GA3), (2-chloroethyl) phosphoric acid (ethephon).