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Leah E. Willis and James E. Motes

Six experiments were conducted to determine the effect of priming on spinach seed performance. Performance was determined by percent, uniformity, and speed of germination after 10 days. In Expt. 1, performance at 22 °C was improved for primed seeds compared to unprimed seeds and germination was >90% for both primed and unprimed seeds. In Expt. 2 (incubator @ 40 °C for 16 h/30 °C for 8 h), germination was reduced for both seed treatments and primed seeds had more germination, but less uniformity than unprimed seeds. In Expt. 3 (incubator @ 40 °C for 16 h/30 °C for 8 h), initial temperatures were 40 °C for 16 h, 40 °C for 8 h, or 30 °C for 8 h. There was an interaction between priming and initial temperature for percent germination, indicating that only primed seeds varied in response to initial temperature. Priming improved percent germination but reduced uniformity and did not influence speed of germination. In Expt. 4 (growth chamber @ 40 °C for 16 h/30 °C for 8 h), priming significantly improved percent seedling emergence and speed compared to unprimed seeds but did not influence uniformity. In Expt. 5 (growth chamber @ 40 °C for 16 h/30 °C for 8 h) initial temperatures were 40 °C for 16 h, 40 °C for 8 h, or 30 °C for 8 h. Priming significantly improved seedling emergence and speed and did not affect uniformity of emergence. Seedling emergence was significantly improved for seeds planted at an initial temperature of 40 °C compared to 30 °C.

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Young Rog Yeoung and Dale O. Wilson

Pregermination techniques of osmotic priming and hydropriming have been used to enhance seed performance on planting Osmotic priming and hydropriming method were compared on the basis of germination performance O2, N2 and air were supplied to 500 ml vessels containing seeds with distilled water or -1.31 MPa PEG solution for 10 days On removing seeds from vessels, seeds were dried back to original water content. There were no differences in total germination between osmotic priming and hydropriming treatments t50 was reduced dramatically from 112 to 32 hours, using hydropriming with air and N2supply for 1 day, compared to 70 hours of osmotic priming. Solute leakage from O2supply of both methods was higher than air or N treatment, Indicating the loss of membrane integrity Hydropriming with O2induced radicle emergence and loss of desiccation tolerance around 28 hours after treatment LEA protein levels were not changed in both treatments except for hydropriming with O2. The timing of desiccation tolerance loss was correlated with that of degradation of LEA protein. O2supply caused the adverse effects on seed performance from both methods 1 day after treatment

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Carlos A. Parera and Daniel J. Cantliffe

In a test to overcome poor seed germination and seedling vigor of sweet corn (Zea mays L.) seeds carrying the shrunken-2 (sh2) mutant endosperm, primed seeds of two sh2 sweet corn cultivars—Crisp N'Sweet 711 (CNS-711) and How Sweet It Is (HSII)—were redried at 15, 20, 30, or 40C and 25% relative humidity after solid matrix priming (SMP). The dehydration rate was significantly lower in `CNS-711' than `HSII' at all temperatures. In both cultivars, the drying temperature after SMP was critical for seed performance. Primed seeds with a higher dehydration rate (dried at 30 or 40C) had better seed vigor, greater field emergence and seedling vigor, lower leachate conductivity and imbibition rate, and a higher respiration rate and glutamic acid decarboxylase activity than primed seeds redried at the lower temperatures or control seeds. Increased incidence of pathogen growth was observed on seeds dried at 15 and 20C relative to those dried at 30 or 40C, probably as a consequence of greater leakage from the seeds at a lower redrying temperatures. Lack of tolerance to dehydration at 15 and 20C was another factor adversely affecting the seeds redried at low temperature. A more rapid dehydration rate at a higher temperature after priming sh2 sweet corn improved many of the physiological characteristics used to measure seed quality and the subsequent emergence and vigor of the seedlings under field conditions.

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Carlos A. Parera and Daniel J. Cantliffe

The effects of the dry-back temperature on sh2 sweet corn seeds primed via solid matrix priming combined with sodium hypochlorite (SMPsh) were studied. Seeds of two sh2 sweet corn cultivars: Crisp N'Sweet 711 (CNS-711) and How Sweet It Is (HSII) were primed via SMPsh. After the treatment, the seeds were dried-back from 50-54% to 6-7% moisture content at 20, 30 or 40C and 25% RH. The rate of dehydration was significantly lower in CNS-711 compared to HSII at all dry-back temperatures. In both cultivars, seed respiration after 4, 16, and 32h of imbibition was greater in those dried at 30 and 40C compared to 20C or non-primed seed. Enzyme activity (glutamic acid decarboxylase activity) was decreased in HSII seeds dried at 20C. There were no differences among treatments in CNS-711. Leakage conductivity was significantly less when the seeds were dried-back at 30C or 40C compared to 20C or nonprimed seeds. Laboratory germination and seedling fresh weight were greater in seeds dried-back at 30C compared the others temperatures or non-primed seeds. The low rate of desiccation at 20C (30h and 8h in CNS-711 and HSII, respectively) may not suppress germination events after priming, thus damaging the embryo during dry-back. This work demonstrated the importance of dry-back temperature to the efficacy of SMPsh seed treatment in sh2 corn.

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Wlodzimierz Ptasznik and Anwar A. Khan

The effects of various drying conditions on seed quality and performance of matriconditioned `Bush Blue Lake 47' snap bean (Phaseolus vulgaris L.) seeds were studied. An exponential model based on the Page equation provided a good fit (R2 = 0.9) to changes in moisture content during drying. Drying matriconditioned seeds with high initial moisture content (47.2%) for 5 to 6 hours at 35C, 30% to 35% relative humidity, and 0.7 to 1.4 m·s-1 air velocity (v) retained, and in some cases augmented, the benefits derived from conditioning. Matriconditioning greatly reduced electrolyte leakage (34.3 vs. 94.7 μS·cm-1·g-1 for nontreated seeds); drying to 15% moisture content at 0.7 or 1.4 m·s-1 v moderately increased the leakage rate (59.1 to 60.9 vs. 34.3 μS·cm-1·g-1), while drying at 0.02 m·s-1 v (ambient) increased the rate to that of nontreated seeds. The leakage rate remained low (43.6 to 50.8 μS·cm-1·g-1) in matriconditioned seeds dried to 22% moisture content at all air velocities. In growth-chamber studies, rapidly drying matriconditioned seeds to 15% moisture content at 1.4 m·s-1 v improved the emergence percentage over that of nontreated seeds, increased the shoot fresh and dry weight over that of nontreated and nondried matriconditioned seeds, and increased the shoot fresh weight over that of seeds dried at 0.02 or 0.7 m·s-1 v. Drying matriconditioned seeds to 15% moisture content at 0.7 m·s-1 v improved plant fresh weight over that produced by nontreated seeds. Rapid drying to 22% moisture content at 1.4 or 0.7 m·s-1 v improved only shoot fresh weight over that of nontreated seeds. In a 1992 field planting, percent emergence of matriconditioned seeds dried at 0.7 or 1.4 m·s-1 v was similar to that of nondried matriconditioned seeds and higher than that of nontreated seeds. No significant differences were noted in plant yield among the treatments.

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Anwar A. Khan

ACC-derived ethylene production was used as an index of seed vigor of lettuce (Lactuca sativa L.), cabbage [Brassica oleracea (Capitata Group)], tomato (Lycopersicon esculentum Mill.), snap bean (Phaseolus vulgaris L.), and sweet corn (Zea mays L.) seeds. Seeds were aged at 40C and 93% relative humidity over saturated solution of KH2PO4 for various times to obtain seeds of differing vigor. Naturally aged lettuce seeds, differing in vigor, were also used. Depending on the seed type, 0.25 to 2 mm ACC (saturating dose) was needed to produce maximal amounts of ethylene. Seeds in the presence of ACC produced a much larger amount of ethylene than those in the absence of ACC, the ACC-derived ethylene could be detected before germination, and ACC had no adverse effect on germination. ACC-derived ethylene production paralleled vigor loss as determined by a decrease in percentage germination over a soak period required for complete germination of nonaged seeds (16 hours for lettuce, 24 hours for cabbage, and 48 hours for tomato and sweet corn), an increase in mean germination time (determined for lettuce only), and a decrease in seedling growth (determined for snap bean only). Second degree polynomial and logarithmic equations generated for the relationship of ACC-derived ethylene production to germination or growth parameters following seed aging, provided good to excellent fit. As a vigor test, the ACC-ethylene procedure has several advantages over the non-ACC ethylene procedure: It improves the sensitivity of the test by enhancing ethylene production, permits detection of small differences in vigor, and allows detection of ethylene before germination within a few hours of soaking. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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Clíssia Barboza da Silva, Julio Marcos-Filho, Pablo Jourdan, and Mark A. Bennett

). Better seed performance after seed priming is, in part, the result of a greater accumulation of germination metabolites ( Sliwinska et al., 2009 ; Varier et al., 2010 ), and also due to the efficient repair of damage to DNA and membranes, which is

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Mark A. Bennett, Nancy W. Callan, and Vincent A. Fritz

Disease management is an important step in any crop establishment system. Emergence of field-seeded crops may take several weeks for many species and represents a vulnerable stage of plant growth. This paper considers various biological, chemical, and physical seed treatments for improved seed performance. The role of seed quality and cultural practices in seedling establishment also is reviewed. Multidisciplinary approaches to improving horticultural crop establishment are promising.

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Jabe E. Warren and Mark A. Bennett

Drum priming enhances seed performance without the waste and additional materials associated with conventional osmotic or matric priming techniques. Sweet corn (Zea mays L.) se (`White D' Lite') and sh2 (`WSS-4948') endosperm seeds were hydrated using drum priming at 25 °C for 6 hours. During each cycle, 125-g seed samples were exposed to 1.6, 3.2, 4.8, or 6.0 mL of distilled water and then rotated in a drum for 1 hour to ensure uniform uptake. At the end of this period, samples of 100 seeds (each) were removed and moisture content was determined. Drum priming hydrated all seedlots gradually, with increasing time required at reduced water levels for individual seedlots to achieve the desired moisture content (25% to 30%). Drum priming may provide a better alternative to conventional systems of priming.

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Sharon A. Duray and Fred T. Davies Jr.

Plant propagation instructors are challenged to develop laboratory exercises that demonstrate the theoretical aspects of seed germination. Seed priming or osmoconditioning is a relatively new technigue that has been shown to improve seed performance in horticultural crops. An esaily constructed seed priming system was designed using a pair of 2-liter glass jars, 2 aquarium pumps and air tubing. Eight sets of 40 seeds were each wrapped in coffee filters and laced in aerated treatment solutions consisting of 50 mmole K H2P O4 or an untreated control of distilled water. All seeds were treated or 0, 1, 3 or 5 days. Upon completion, seeds were rinsed, dried and placed into petri dishes containing moist filter paper to observe germination. A good test species for this exercise is Vinca rosea which typically has a poor germination percentage and rate. Seeds primed for 3 and 5 days significantly enhanced both germination percentage and rate in Vinca.