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Dina Margaret Samfield, Jayne M. Zajicek, and B. Greg Cobb

Seeds of tickseed (Coreopsis lanceolata L.) and purple coneflower [Echinacea purpurea (L.) Moench] were primed in aerated solutions of distilled water or 50 or 100 mM salt (potassium phosphate, pH 7.0) at 16C for 3, 6, 9, or 12 days. Coreopsis seeds primed in the 50 mM buffer germinated the most rapidly and uniformly, and, under stress conditions in the greenhouse, resulted in a faster-growing, more-uniform crop than other treatments. Seeds primed in distilled water and the 50 mM buffer germinated faster and at higher rates at suboptimal temperatures in the laboratory than nonprimed seeds. Priming of Echinacea purpurea seeds for 6 or 9 days in distilled water or in the 50 mM buffer resulted in faster, more-uniform germination than other treatments. Seedling emergence under stress conditions was improved by all priming regimes, with best emergence occurring in treatments that lasted > 3 days. Priming also increased germination rates of E. purpurea at suboptimal temperatures in the laboratory.

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Richard L. Hassell, Robert J. Dufault, and Tyron L. Phillips

Ten triploid and 25 diploid watermelon (Citrullus lanatus) selections were evaluated to determine the temperature range and length of test for which germination index (rate of germination over time) and germination percentages were maximum for expediting vigor and seed testing practices. Temperature interacted with watermelon selection indicating that certain selections germinated faster within specific, but differing temperature ranges. Within 2 days after starting the germination process, 90% of triploid selections and 96% of diploid selections germinated to their greatest level and prolonging germination data collection for one week did not change this relationship. Although optimal temperature ranges may differ among the selections, the one temperature within the range common for all selections evaluated that maximized germination was 85 to 90 °F (29.4 to 32.2 °C) for diploids and 85 °F for triploids.

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Claudinei Andreoli and Anwar A Khan

Emergence and stand establishment of pepper and tomato seeds often are slow and erratic, particularly under stress conditions. Field emergence trials sometimes have not responded to priming in pepper. In this study, we examined the combining effect of matriconditioning with GA4+7 to hasten germination and improve stand establishment of pepper and tomato seeds. The results showed that, in all cases, even under stressful conditions, the combined matriconditioning plus GA treatment was effective in improving germination and emergence of pepper and tomato seeds. Emergence was improved in 20% when seeds were treated with GA4+7 up to 200 mM. Thus, matriconditioning during which germination is suspended, provides a unique means to rapidly and efficiently digest the endosperm by GA-induced enzymes and reduce not only the mechanical restraints but also provide the energy for embryo growth.

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Jian Fana, E.E. Roos, C.W. Vertucci, and F.D. Moore III

Seed water content has been considered the most important factor controlling various physiological reactions in seeds. Hydration/dehydration affects many physiological reactions, including the “priming effect” and “accelerated aging,” depending on time and level of hydration. Corn seeds (11% mc) were subjected to six cycles of hydration (2 h) and dryback or one hydration of 12 h and dryback. Following soaking, seeds were dried quickly by using a fan to remove moisture and then equilibrated to their initial mc. Seeds were evaluated for germination and vigor (root length and leachate conductivity). Percent germination of seeds treated with either continuous or intermittent hydration and dehydration was >90%. Vigor of seeds hydrated for successive 2-h cycles initially increased (priming effect); however, after the sixth cycle, vigor was equal to the nontreated control seeds. One cycle of hydration for 12 h then dryback had no effect on germination but did increase vigor. We are now extending the number of 2-h hydration periods to 10 to determine when damage occurs from these cycles. Our objective is to better understand the relationship between seed hydration and physiological changes associated with seed priming, accelerated aging, and imbibition damage.

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S. Pérez-González

A highly significant correlation was observed between time of bloom of individual peach trees [Prunus persica (L.) Batsch.] and number of days required for resulting selfed seed to reach 80% germination on both local (r = 0.71) and introduced (r = 0.87) genotypes that exhibited a wide range in time of blossom. When genotypes with low chilling requirement (LCR) were pollinated with high chilling requirement (HCR) pollen sources, germination was delayed up to 16 days with respect to seeds that originated from selfing, while LCR pollen sources on late-blossoming genotypes accelerated germination 20 to 24 days.

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Lucette Laflamme, Nicolas Tremblay, and Marie-Hélène Michaud

Angelica is grown in Quebec (Canada) for its root-bound medicinal properties. Matol Botanique Int., a major user of Angelica extracts, decided 4 years ago to promote local production in order to secure supplies and quality. However, the crop has to be started from seed that show low and variable germination behavior. Emergence occurs after ± 12 days and most of the germination if obtained after 20 to 40 days depending on seed origin and test conditions. Maximum germination ranges from 6 to 57%. Three treatments were first compared in order to stimulate germination: seed soaking in warm water for 24 h, watering germination trays with algae extracts and placing floating row covers over the trays. Angelica germination was significantly improved only by row covers with a maximum of 24% vs 19%. Results were obtained from experiments with other techniques (stratification, seed conditioning, etc,...) to further improve germination.

2Working for the Horticultural Research Centre, Laval University, Que.

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Julia L. Bohnen and Anne M. Hanchek

The Legislative Commission on Minnesota's Resources funded a two year research project to promote expansion of the native wildflower and grass seed industry in Minnesota. Production of seeds and plants for landscaping and restoration is a growing sector of the horticultural industry, yet documentation of production techniques is sketchy due in part to the large number of species. The species Lilium philadelphicum (wood lily), Phlox pilosa (prairie phlox), and Spartina pectinata (prairie cordgrass) were selected for further analysis of germination requirements. These species were noted by producers as having poor and/or unreliable germination. Cold moist stratification and gibberellic acid (GA) treatments were applied Total percent germination and mean days to germination were calculated and analyzed after 30 days under greenhouse growing conditions. Stratification improved total percent and mean days to germination in L. philadelphicum. P. pilosa responded to treatment by both stratification and GA. Four weeks of stratification may be the best method for decreasing mean days to germination while obtaining adequate total percent germination for S. pectinata.

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Laura G. Jull and Frank A. Blazich

Cones of six provenances (Escambia Co., Ala., Santa Rosa Co., Fla., Wayne Co., N.C., Burlington Co., N.J., New London Co., Conn., and Barnstable Co., Mass.) of Atlantic white cedar [Chamaecyparis thyoides (L.) B. S. P.], were collected Fall 1994 (Alabama, North Carolina, New Jersey, and Connecticut), Winter 1995 (Massachusetts), or Fall 1995 (Florida). Cones were dried for 2 months, followed by seed extraction and storage at 4°C. Seeds were then graded and stratified (moist-prechilled) for 0, 30, 60, or 90 days. Following stratification, seeds were placed at 25°C or an 8/16-hr thermoperiod of 30°/20°C with daily photoperiods of 0, 1, or 24 hr. Germination was recorded every 3 days for 30 days. Temperature, stratification, and light had significant effects on germination. However, responses to these factors varied according to provenance. Averaged over all treatments, the Alabama provenance exhibited the greatest germination (61%), followed by the Florida provenance (45%), with the remaining provenances ranging from 20% to 38%. However, there were specific treatments for each provenance that resulted in germination > 50%. The three southern provenances (Alabama, Florida, and North Carolina) required 30 days of stratification for maximum germination. They did not exhibit an obligate light requirement, but photoperiods ≥ 1 hr increased germination greatly over seeds in darkness. In contrast, the northern provenances (New Jersey, Connecticut, and Massachusetts) had an obligate light requirement. These provenances only required 30 days stratification with continuous light for maximum germination. When subjected to a 1-hr photoperiod, seeds from the northern provenances required longer durations of stratification for maximum germination. Regardless of the length of stratification, the New Jersey provenance required a 24-hr photoperiod to maximize germination. When averaged over all treatments, total germination for each provenance was greater at 30°/20°C than 25°C (43% vs. 31%).

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Jonathon I. Watkinson and Wallace G. Pill

Following dry storage for 5 or 11 months (new and old seeds, respectively) at 5 °C, less than 10% of the seeds of Indiangrass germinated as determined by a standard germination test. We attempted to increase germination by subjecting seeds to dormancy-breaking treatments, including sodium hypochlorite soak (5.25% v/v NaOCl; 20 or 60 min), prechilling (5 °C for 2 weeks), gibberellic acid during germination (GA3, 1000 mg·L-1), and combinations thereof. Treatment with NaOCl increased the germination of non-prechilled seeds only when they were germinated in GA3; a 60-min soak in NaOCl increased germination to 53% and 65% in new and old seeds, respectively. Prechilling increased germination to 65% and 47% in new and old seeds, respectively. Germination of new, prechilled seeds was increased further to 86% by either a 20-min soak in NaOCl or germination in GA3. Germination of old, prechilled seeds was not promoted further by treatment with NaOCl, but was increased to 67% by germination in GA3. Since NaOCl treatment alone failed to promote germination, we examined the effects on seedling emergence and growth of providing GA3 at 1000 mg·L-1 during the 2-week prechilling period. While prechilling alone increased emergence to an average 34% for new and old seeds, prechilling with GA3 increased emergence to 75% and 50% for new and old seeds, respectively. These treatments did not influence seedling shoot dry mass. Seed exposure to GA3 during rather than after prechilling was more effective in promoting Indiangrass establishment.

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Jimmy L. Tipton

Seed scarification and stratification (moist-prechilling) requirements of Mexican redbud [Cercis canadensis var. mexicana (Rose) M. Hopk.] and evergreen sumac (Rhus virens Gray) and the effects of temperature on final percent germination, maximum germination rate, and inflection time (time to maximum germination rate) for the above species plus seeds of mealy sage (Salvia farinacea Benth.) were investigated. Maximum predicted germination from a quadratic response surface was 95% after 62 minutes of concentrated sulfuric acid scarification plus 35 days of stratification for Mexican redbud, and 59% after 52 minutes of scarification plus 73 days of stratification for evergreen sumac. Mexican redbud germinated at 24 to 31C. Predicted optima for final percent germination, maximum germination rate, and inflection time were 100% at 28C, 30% germination per day at 31C, and 4 days at 29C, respectively. Evergreen sumac germinated at 21 to 31C. Final percent germination for this species declined with increasing temperature from a predicted maximum of 52% at 21C, whereas maximum germination rate increased with temperature to a predicted maximum of 69% germination per day at 31C. Inflection time was high at both extremes with a predicted minimum of 10 days at 25C. Mealy sage germinated at 21 to 34C. Predicted optima for final percent germination, maximum germination rate, and inflection time were 96% at 25C, 104% germination per day at 27C, and 3 days at 28C, respectively.