Abstract
Pregerminated snapdragon seed was damaged to different extents by low-temperature storage for 4 or 8 days in 3 hydrophilic gels or deionized water. Poststorage viability and vigor decreased as a result of storage, but for apparently different reasons. Medium pH was correlated with poststorage vigor, whereas the gas-exchange capacity of the storage media was correlated with poststorage viability. Seed germination and radicle elongation within the gel was also stimulated when the gas-exchange capacity of the storage medium was increased. Enzymatic generation of oxygen within the gel increased both seed germination and radicle elongation, which suggests that the oxygen diffusion rate specifically was limiting these phenomena.
Seed production in the family Cucurbitaceae is more complicated than in dry-seeded grain crops because seeds mature within a moist fruit and are often held at high moisture content for several weeks before seed harvest. Muskmelon (Cucumis melo L.), a member of this family, was used as a model system to contrast seed development with crops that are dry at maturity. A detailed time course for `Top Mark' fruit and seed development is presented based on previous studies. In muskmelon fruit, precocious germination is inhibited osmotically by the low water potential of the surrounding fruit tissue. Muskmelon seeds exhibit primary dormancy that affects viability very early in development but has a greater effect on seed vigor and is removed by afterripening during dry storage. Osmotically distended or fish-mouth seeds are dead seeds that occur in cucurbit seed lots after aging kills the embryo without disrupting the semipermeable endosperm that completely surrounds and protects the embryo. Cucurbit seed crops should be harvested before the onset of fruit senescence to prevent aging of the seeds inside. Open-pollinated cucurbit seed crops are frequently once-over mechanically harvested. Mechanical harvesting combines seeds from many stages of development into a single seed lot, which may adversely affect quality and increase seed to seed variability. Hand harvesting cucurbit fruit at the optimal stage of development could improve seed quality in some instances but is more costly and time consuming and would increase production costs.
Native turfgrasses have received greater attention in recent years because of their usefulness in growing in areas where many other grasses cannot. Saltgrass (Distichlis spicata) has good salt tolerance, but the natural germination rate for the seed is low. This is most likely due to the thickness of the seed coat inhibiting normal imbibition of water. Previous research in our laboratory has demonstrated increased germination with hand-scarification. The purpose of this research was to compare germination rates of machine-scarified, hand-scarified, and nonscarified seed. Scarifying the seeds by hand results in greater uniformity, but the operation is tedious and time-consuming. Machine scarification is quick, but the seeds have reduced uniformity. Two seed lots, one designated “Modoc” and one designated “Granite,” were compared in laboratory and field germination tests. Preliminary observations have shown that “Granite” seed had somewhat higher viability and vigor than the “Modoc” seed. Significantly greater germination occurred with scarification when seeds were germinated at 14 h of light at 30 °C and 10 h of darkness at 20 °C in the laboratory. Although scarification treatments were similar with the “Granite” seeds, near 80% germination, there were significant differences between hand and machine scarification with the”Modoc” seeds; hand scarified seed had greater germination. The field germination experiment had similar results to the laboratory experiments with “Granite” seed. However, scarification did not aid germination of “Modoc” seed. This is thought to be due to low vigor and associated death of seedlings prior to emergence. Preliminary data confirm the low vigor of the “Modoc” seed as compared to “Granite” seed.
Abstract
High proportions of 3x hybrids were obtained from crosses of 4x highly sexual seed parents by 2x pollen parents in Citrus. This is in contrast to the low proportions usually obtained with 4x partly apomictic cultivars as seed parents, or with 4x plants used as pollen parents. Initial survival of small germinating seeds and very young seedlings was low but later growth vigor has been high. Ten 4x and 9 aneuploid (near 3x) plants were identified.
Abstract
Seeds of 14 vegetable and 2 flower species were placed in paper envelopes and submerged in liquid nitrogen (LN2, –196°C) for periods up to 180 days with no adverse effects on germination. Vigor tests with beans (Phaseolus vulgaris L.), lettuce (Lactuca sativa L.), and peas (Pisum sativum L.) also indicated no reduction in germination or vigor after exposure to LN 2. Liquid nitrogen offers promise as a medium for long-term storage of seed germplasm.
Abstract
Deterioration of snap bean (Phaseolus vulgaris L.) seed quality during accelerated aging at 42°C and 100% relative humidity was accompanied by a decline in germination, radicle emergence, hypocotyl length, and ethylene production. Field emergence of 5 seed lots had a highly significant correlation with ethylene production rates when measured after 22 to 23.5 hours of imbibition at 25°. Seed lots that produced low levels of ethylene emerged poorly in the field. Results indicate that determination of ethylene production of imbibed seeds might be a useful method for detecting changes in seed vigor.
Abstract
Lines and cultivars resistant to mechanical damage with white and colored seeds germinated 60–80% compared to under 20% for several major cultivars. Seed damage resistance was associated with transverse cotyledon cracking (TVC) resistance, r = .649, seed coat shattering (SH) resistance, r = .488, and seed coat weight, r = .373. The SH test indicates whether the seed coat is tightly or loosely adhered to the cotyledons. If % seed coat as a proportion of seed weight exceeded 10% and TVC and SH were under 10%, then damage resistance was almost always good. Weakness in any one character resulted in damage susceptibility. Damage resistant lines produced more vigorous seedlings than susceptible lines following seed maltreatment. Damage resistance was correlated, r = .722, with seedling vigor following seed impaction.
Mutant endosperm associated with shrunken-2 sweet corn possesses a high osmotic potential that increases the rate of imbibition. Membrane damage associated with the rapid influx of water during imbibition can play a role in the poor emergence and seedling vigor associated with sweet corn germination. Film-coating as a seed treatment has been used to improve germination and vigor in sweet corn. This improvement may be associated with alterations in the kinetics of imbibition. Two seed lots of shrunken-2 sweet corn, low-vigor `Even Sweeter' and high vigor `Sugar Bowl', were treated with a polymer film-coating and evaluated for differences in water uptake. Imbibition curves were established for nontreated and film-coated seeds. Seeds were weighed every hour for 6 hours and showed a significant difference between the two treatments in fresh weight for both cultivars. This pattern continues throughout the imbibition phase of germination and continues into the lag period. Bulk conductivity tests resulted in no significant mean difference between untreated and film treated seeds after 24 hours. Film treatment assumes characteristics of a hydrophilic polymer. Electrolyte leakage is not reduced and imbibition rate increases by 18% for both varieties of film-coated seeds.
Abstract
‘Miragreen’ garden pea seeds from individual seed lots were sorted into bleached, partially-bleached, and non-bleached categories. Seeds were either soaked for 48 hours in aerated water at 22°C, coated with thiram fungicide, or received no treatment. Seeds were planted in Conover loam soil where damping-off and seedling rot were primarily caused by Pythium ultimum Trow and Fusarium solani (Mort.) Sacc f. sp. pisi (Jones) Snyd. & Hans. No differences in germination in vitro were found among bleached, partially bleached, and non-bleached seeds. However, seedling emergence in the field was greater from untreated non-bleached seeds (69%) than from untreated bleached seeds (30%); emergence from partially bleached seeds (58%) was intermediate. Regardless of degree of bleaching, all seedlings were a normal green color after emergence, and appeared equal in vigor. Pea yields from untreated bleached seeds were less than from untreated non-bleached seeds, apparently because pea-emergence damping off was so much greater with bleached than with non-bleached seeds. No yield differences occurred with fungicide-treated seeds. Soaking partially bleached seeds for 48 hours in aerated water at 22°C prior to planting in April was as effective in improving emergence in artificially infested soil as coating seeds with thiram. However, when seeds were planted in mid-June, the thiram treatment gave higher seedling emergence than the soaking treatment. In general, high yields were achieved by early planting of seeds and minimum root rot.
Generally, sweet corn cultivars (Zea mays L.) carrying the shrunken-2 (sh2) gene have lower germination and seedling vigor than normal or sugary (su) cultivars. Seeds of sh2 `How Sweet It Is' (HSII) and `Crisp N'Sweet 711' (CNS-711) were imbibed for 6 hours. Rapid water uptake, higher seed leakage, and fungal infection were found in HSII, the lower germinating cultivar. Imbibition rate and leakage conductivity were reduced in both cultivars during the first 5 hours at 5C as compared with 25C. Sodium hypochlorite was an effective seed disinfectant. When the seeds were primed with sodium hypochlorite via solid matrix priming (SMP), germination under stressful conditions (soilcold test) was significantly improved in both cultivars. Primed seeds had significantly lower imbibitional rates and leakage conductivity than nonprimed seeds. The superior germination measured in primed and disinfected seeds was possibly due to the lower imbibitional rate and reduced seed fungal infection.