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N. Wartidiningsih and Robert L. Geneve

Germination was evaluated in six seed lots of purple coneflower purchased from four different seed companies. Standard germination percent ranged from 28% to 90% depending on the seed lot. For seed collected in 1989, seed size and stage of development of the seed at harvest could not account for the wide variability in seed germination observed in the purchased seed lots. preconditioning the seed with either cold stratification (10°C for 10 days) or osmotic priming (PEG or salt solution at -5 bars for 5 days) increased the rate of germination and the overall percent germination for all seed lots and dramatically improved germination in the poor germinating seed lots. Preconditioning appears to overcome either a shallow physiological dormancy or compensates for seeds with poor vigor or quality. In either case, seed preconditioning drastically improved seed germination (rate and percent) in greenhouse and field tests for purple coneflower.

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William J. Carpenter and Joseph F. Boucher

The optimum conditions for priming pansy (Viola × wittrockiana) seeds were in aerated osmotic solutions of polyethylene glycol 8000 (PEG 8000) at – 1.0 MPa for 7 days at 15C. Priming at – 0.8 MPa and 15C caused 8% to 26% of seeds to germinate during 4 to 13 days of priming. Increasing numbers of abnormal seedlings developed when priming was extended beyond 7 days. Final germination percentages were better in laboratory studies at 35C for primed (51%) than nonprimed (10%) seeds. Removal of the mucilage released by the seed with 240 g KOH or 170 g NaOH/liter for 15 or 30 seconds during priming did not affect total germination percentages, but did improve seed handling. Primed seed had higher, faster, and more uniform germination than nonprimed seeds after sowing in growing medium in plant growth chambers or greenhouses.

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W. A. Erb, A. D. Draper, and H. J. Swartz

Abstract

Two methods of evaluating seedling drought resistance in Vaccinium (blueberry) spp. were examined. Twenty interspecific populations were greenhouse-grown and either matric-stressed in a dry 1 sand : 1 soil medium or osmotic-stressed in a nutrient solution containing polyethylene glycol (PEG). In both tests, population means were separated statistically by shoot damage ratings. The correlation (r = 0.46) between the two tests was positive and significant. Progenies of clones JU64 and JU62, which are sister seedlings (V. myrsinites Lamark × V. angustifolum Aiton), were the most drought-resistant. The soil screening test appeared more accurate because it grouped populations with common parentage. These tests indicated that the progenies differ in genetic capacity to resist drought.

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Stuart W. Akers and Kevin E. Holley

Abstract

Potential benefits of priming seeds were first indicated by Levitt and Hamm in 1943 (14), reported for vegetable seed in 1963 by Ells (7), and summarized in 1975 by Hey-decker et al. (11). Effective priming causes the treated seed to germinate earlier and with greater uniformity than untreated seed (11). To date, the technique of priming seeds has been used to solve problems concerning thermodormancy (9), cold soil temperatures (15), and to increase the rate and uniformity of crop emergence (7, 10, 11). However, the methodology of priming, especially for PEG solutions, has not been readily adaptable to handling the large amounts of seed that would be required for commercial use (4, 10). Although the successful use of the SPS to ‘bulk’ prime carrot (12) and pepper (3) seeds has been reported, the design of the SPS and the methodology of its use have not been adequately described. Therefore, this report describes the SPS and the methodology that makes it functional.

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John C. Peterson, John N. Sacalis, and Dominic J. Durkin

Abstract

Relationships were examined among water deficits, ABA content of leaf tissue, and leaf abscission in intact Ficus benjamina L. (weeping fig). Water deficits were imposed by withholding water from plants growing in sand and by raising the osmotic potential of water culture solutions through the addition of PEG 6000. Unconjugated ABA was quantitatively analyzed using gas chromatography. A strong inverse linear correlation existed between ABA content of leaves and plant water potential. No relationships between ABA content and leaf abscission were observed. ABA content in leaves collected from plants growing in a greenhouse, having a plant water potential of −0.5 bar, was about 75 fold greater than the ABA content of leaves collected from plants maintained in a controlled environment room, having plant water potentials of −8.0 bar. Results indicate that ABA does not independently regulate leaf abscission in Ficus benjamina.

Open access

Dariusz Swietlik, R. F. Korcak, and Faust Miklos

Abstract

The effect of polyethylene glycol (PEG)-induced water stress on stomatal and nonstomatal inhibition of photosynthesis of apple seedlings (Malus domestica Borkh.) grown in solution culture was investigated. Water stress was applied gradually by modifying the nutrient solution water potential daily to a minimum of -8.0 bar. Nutrient solution of less than or equal to water potentials -6 bar decreased net and gross photosynthesis rates. Stomatal and nonstomatal factors were responsible for photosynthetic inhibition. Nonstomatal inhibition of photosynthesis appears to be due to decreased capacity for CO2 fixation and not increased photorespiration. The ratio of gross to net photosynthesis was not affected. A higher level of water stress was required to affect mesophyll resistance than stomatal resistance and/or there was a lag time for mesophyll resistance to respond to stress.

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David A. Francko, Kenneth G. Wilson, Qingshun Q. Li, and Maria A. Equiza

Hardiness Zone ratings. Each of the five ingredients in our spray was chosen for its specific mode of action in hypothetically improving resistance to cold in plant tissues. In animals and insects, polyols like polyethylene glycol (PEG) appear to enhance

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Rufaro Madakadze, Ellen M. Chirco, and Anwar A. Khan

The effect of preplant conditioning on germination of three flower seeds, Bupleurum griffithii (Tourn.) L. (thorough-wax), Ammi majus L. (greater ammi), and Cirsium japonicum DC. Per. (Japanese thistle), were studied. Seeds were osmoconditioned with -1.2 MPa polyethylene glycol 8000 (PEG) solution and matriconditioned with moist Micro-Cel E (ratio of 2 seed: 0.6 carrier: 3 water by weight for Bupleurum and Cirsium; for Ammi the ratio was 2:1.4:6) and moist expanded vermiculite #5 (the ratio was of 2 seed: 0.6 carrier: 2 water for Bupleurum). In some treatments, water in the matriconditioning mixture was replaced with 1 mm gibberellin A4+7 (GA) or 0.2 % KNO3. In Bupleurum, matriconditioning with Micro-Cel E was generally superior to matriconditioning with vermiculite or osmoconditioning with PEG. A 4-day matriconditioning with Micro-Cel E and germination in the dark reduced the period required for 50% (T50 of final germination by 4 days and improved the percentage germination at 20C (73 % vs. 95%), compared to nonconditioned seeds germinated in the dark. The treatment also improved the percentage of germination at 15C (68% vs. 95%) and effectively removed the thermoinhibition of germination at 25 and 30C. Germination was inhibited to a greater extent for seeds kept in the light during matriconditioning and germination than for seeds conditioned in darkness and germinated in light or conditioned in light and germinated in darkness. Nitrate added during conditioning in light prevented inhibition of germination, provided seeds were kept in darkness during germination. In A. majus, germination in light after 4-day matriconditioning reduced the T50 by ≈2 days, but had little effect on percentage germination. Both GA and irradiance equally promoted germination when added during osmoconditioning, with nitrate having no effect. In C. japonicum, a 4-day matriconditioning or a 7-day osmoconditioning reduced the T50 of germination by -2 days and improved the percentage germination to some extent. Neither irradiance nor nitrate had any significant effect.

Open access

Anna J. Talcott and William R. Graves

germination in P. trifoliata , the need for a more precise procedure exists, and there is no information about the germination of seeds of P. crenulata . Soaking seeds in water with dissolved polyethylene glycol (PEG), called osmopriming, has been used to

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Joseph A. Fiola and Robert J. Lengyen

High-density, annual, strawberry production systems (“plasti-culture”) have shown high productivity under New Jersey conditions; however, cultural practice and variety research is needed to increase profitability. The system includes raised beds, plastic mulch, trickle irrigation, and double-row 12 × 12-inch plant spacing. Polypropylene floating rowcovers were applied in December and removed in early April when flowers were visible under the cover. Treatments included comparisons of plugs and dormant crowns of the cultivars Chandler and Allstar, planted at multiple planting dates, on white or plastic mulch, in “matted-row” (single row at 18-inch spacing; peg runners through plastic) or high-density production systems. The plug plants were superior to dormant crowns. Black plastic was best all planting dates with plugs; `Allstar' performed best on black on the early planting dates, while `Chandler' preferred the white for the early planting dates. Both `Allstar' and `Chandler' had commercially profitable yield, fruit weight, and quality. “Matted-row” system on plastic is high-yielding but labor-intensive. Late-summer plugs on black plastic is best overall.