(pp. 1-6)
The Effect of Liquid Nitrogen on Alfalfa Seed Viability, Emergence, and Broken Cotyledons
L.E. Wiesner, J.E. Laufmann, P.C. Stanwood, and L.J. Wheeler
ABSTRACT:
Liquid nitrogen (LN2) seed storage has great potential for longterm preservation. However, some legumes are damaged following exposure to LN2. Exposure of alfalfa (Medicago sativa L. subsp. sativa) seed to LN 2 was investigated to determine effects on germination, viability, broken cotyledons, emergence, and dry weight.
Treatments evaluated were: LN2 liquid cooling (-196°C) with rapid (35°C) or normal (room temp) warming, LN2 vapor phase cooling (-160°C) with normal warming, hand scarified LN2 vapor phase with normal warming, hand scarified, and non-scarified control. Prior to LN2 treatment, average percentage of hard seed of the four seed lots was 74% and average seed moisture content was 5.9%. Alfalfa accessions containing a high percentage of hard seed (up to 79%) had cotyledon breakage when exposed to LN2 vapor phase (-160°C) for 24 h. Cotyledon breakage was reduced when seed was scarified prior to LN2 exposure. Emergence was not significantly affected by any treatment except LN2 vapor phase with normal warming and the non-scarified control which had significantly less emergence due to hard seed content. Non-scarified control seedling weight was 80% heavier than LN2 liquid phase cooling with either rapid or normal warming. This study suggests that cotyledon breakage of alfalfa seed is associated with hard-seededness usually found in newly harvested seed and that cotyledon breakage reduces seedling growth.
Additional index words: scarified, storability, hard seed
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(pp. 7-15)
Light Improves Reproducibility of Sweet Corn Seed Germination Tests1
Dale 0. Wilson Jr. and Richard C. Lawson2
ABSTRACT:
Germination of shrunken2 sweet corn seed is subject to poor reproducibility when tested by different seed laboratories. This project sought to measure reproducibility and improve reproducibility by providing light during germination testing. A referee germination test with six sweet corn seedlots was performed in 11 laboratories under light and in darkness.
Three of the lots gave rise to highly variable germination percentages and inconsistent ranking of lots among laboratories. This resulted from unstable proportions of seedlings with primary leaves less than 1/2 the length of the coleoptile, abnormals under AOSA rules. Between-laboratory standard deviation ranged from 4 to 25% (avg. 14 %) when germination was performed in the dark, and from 2 to 21% (avg. 10%) when germination was performed under light. In the dark, laboratory means ranged from 42 to 82% (avg. 75%). Under light, laboratory means ranged from 65 to 90% (avg. 77%). We suggest that the AOSA "Rules for Testing Seeds" be changed to require that sweet corn seed be germination-tested under light.
Additional index words: Referee, seedling description, variability, tolerance, standardization rules, light requirement, shrunken2, sh2, maize, Zea mays L.
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(pp. 16-20)
Effect of NaCl Concentration and Temperature on Germination of 'Tam Veracruz'
Chile Seed (Capsicum annuum L.)1
ANNE K. CARTER2
ABSTRACT:
Cool soil temperatures at planting slow chile (Capsicum annuum L.) seed germination and reduce stand establishment. Seed priming is a method used to increase the percent and rate of germination. This study was initiated to examine the effects of NaCl priming on total germination and the rate of germination under suboptimal temperature conditions. Seeds of 'Tam Veracruz' chile were primed at 23°C for 5 days in double-distilled H20, or 0.2,0.4, or 0.6 M NaCl solution (equivalent to an osmotic potential of -0.89 MPa, -1.77 MPa, and -2.66 MPa, respectively).
After priming, the seeds were dried on paper towels at 23°C for 2 days.Treated seeds and nonprimed seeds (control) were then germinated in H20 in Petri dishes in a 15°C or 23°C incubator. Germination was recorded daily until no more seeds germinated for four days. The final germination percentage (FGP) and the germination velocity coefficient (GVC) were calculated to evaluate the treatments. Over 70% of the HnO-soaked seeds germinated during priming, and thus, were not used in the germination study. Priming had little effect on the FGP at either 15°C or 23"C, as all treatments (including the control) had germination percentages above 96%. The GVC of primed seed was greater than the unprimed control. This response was more pronounced at 23°C than at 15°C. Further, the GVC decreased as the NaCl concentration increased from 0.2 M to 0.6 M. These data would suggest that priming 'Tam Veracruz' chile seed for 5 days at 23°C in 0.2 M NaCl would increase the germination rate at temperatures from 15°C to 23°C.
Additional index words: pepper, seed priming, seed treatment, Capsicum
annuum L.
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(pp. 21-29)
The Effect of Storage Conditions on Canola (Brassica napus L. ) Seed Quality1
S. G. Elias and L. 0. Copeland2
ABSTRACT:
This study was conducted to measure the rate of seed deterioration of canola under different storage conditions and evaluate different methods of measuring deterioration. Seed lots of spring canola cultivar, Topas, and two winter cultivars, Liborius and Libravo, were artificially aged to produce sub-lots of three different quality levels. All lots were stored for two years under two environments: 5"C/75% RH and 22"C/30% RH. Standard germination, cold tests, and conductivity tests were used to determine seed deterioration after 4,10, 17, and 24 months of storage.
As the initial quality of seed decreased, its relative storability decreased. The results of all three quality evaluation tests for all lots, with some exceptions, did not decrease significantly during the first 10 months of storage. A gradual decline in seed quality occurred during the following 14 months. All tests were suitable for assessing canola seed quality. The results of all tests were significantly correlated with each other. The study demonstrated the importance of testing the quality of artificially aged seed. lots stored for more than ten months under such storage conditions.
Additional index words: Conductivity test, lipid autoxidation, artificial
aging.
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(pp. 30-42)
Potassium Leakage From Artificially Aged Pea (Pisum sativum L.) Embryos During Imbibition
P.M. Cortes* and S.C. Spaeth2
ABSTRACT:
The loss of intracellular materials from seeds during imbibition has been used as an index of seed quality and vigor. Information about the origin of the leachate and the manner in which loss is affected by aging is needed to improve the interpretation of leakage measurements. In order to identify the origin and characterize the effects of aging on loss, a compartmental analysis was done on the potassium efflux from submerged pea (Pisum sativum L.) embryos during imbibition.
Potassium activity in the mechanically stirred solution, buffered to pH 6.5, was monitored with a potassium ion-selective electrode for the initial 4 h after the dry embryo began to imbibe.The kinetics of efflux from both control and aged embryos fit a double exponential curve, consistent with efflux from two compartments. One compartment exchanged rapidly with a half-time of approximately 7 min, while the other compartment, which accounted for most of the leaching potassium, had a half-time for exchange of about 2 h. Aging increased the amount of potassium available for efflux from both compartments and possibly decreased the half-time for exchange from the slowly-exchanging compartment.
Additional index words: aging, compartmental analysis, embryo,leakage, Pisum sativum, potassium
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