The assessment of seed quality and physiological potential is essential in seed production and crop breeding. In the process of rapid detection of seed viability using tetrazolium (TZ) staining, it is necessary to spend a lot of labour and material resources to explore the pretreatment and staining methods of hard and solid seeds with physical barriers. This study explores the TZ staining methods of six hard seeds (Tilia miqueliana, Tilia henryana, Sassafras tzumu, Prunus subhirtella, Prunus sibirica, and Juglans mandshurica) and summarizes the TZ staining conditions required for hard seeds by combining the difference in fat content between seeds and the kinship between species, thus providing a rapid viability test method for the protection of germplasm resources of endangered plants and the optimization of seed bank construction. The TZ staining of six species of hard seeds requires a staining temperature above 35 °C and a TZ solution concentration higher than 1%. Endospermic seeds require shorter staining times than exalbuminous seeds. The higher the fat content of the seeds, the lower the required incubation temperature and TZ concentration for staining, and the longer the staining time. And the closer the relationship between the two species, the more similar their staining conditions become. The TZ staining method of similar species can be predicted according to the genetic distance between the phylogenetic trees, and the viability of new species can be detected quickly.

Seed dormancy and soil longevity characteristics of three weedy cowpea [Vigna unguiculata (L.) Walp.] cultivars were investigated. Seed germination was maximum at 40 C; however, ‘Clay’ had greater germination than ‘Black’ or ‘Red Ripper’ cowpea at temperatures ≥ 20 C. Concentrated sulfuric acid soaks, hot (70 C)-water soaks, and piercing the seed coat promoted germination. Seed with an initial water content of 12.3% were stored at relative humidities ranging from 0 to 60% at 25 C. After 4 weeks of storage at relative humidities of 0 to 50%, seed water content varied from 4.6 to 11.4%. Germination and hard seed content was 11% or more and 89% or less, respectively, for seed with water content ranging from 6.9 to 11.4%. Except for seed with an initial water content of 6.9%, cowpea seed water content increased after 3 weeks of storage in a 70% relative humidity environment. Rehydration increased germination for seed with initial water content of 9.2% or more, but not for seed with initial water content of 8.4% or less. In mid-November 1981 and 1982, Black, Clay, Red Ripper, and sicklepod (Cassia obtusifolia L. # CASOB) seed were buried at soil depths of 2.5, 7.5, and 15 cm for 3, 6, and 9 months. Seed survival of Black and Red Ripper was similar to that of sicklepod; however, longevity of Clay seed was less than sicklepod. Survival was greater for seed buried in 1981 than in 1982 because of low seed water content of the 1981 seedlots.

Seed of 41 economically important weed species of the Great Plains region of the United States were buried 20 cm deep in soil in eastern and western Nebraska in 1976. The 41 species consisted of 11 annual grass, 14 annual broadleaf, 4 biennial broadleaf, and 12 perennial broadleaf species. Weed seeds were exhumed annually for germination tests the first 9 yr, then after 12 and 17 yr. Germination percentages at the two burial locations averaged over 0, 1 to 4, 5 to 8, and 9 to 17 yr of burial were 57, 28, 9, and 4% for annual grass; 47, 26, 16, and 11 % for annual broadleaf; 52, 49, 44, and 30 % for biennial broadleaf; 36, 18, 13, and 8% for perennial broadleaf; and 47, 26, 16, and 10% for all 41 weed species, respectively. Biennial broadleaf weeds showed the greatest seed germination over years. Annual grass weeds showed less seed germinability over 17 yr of burial than annual broadleaf weeds and perennial broadleaf weed species were intermediate. Weed seed germinability in soil was greater in the reduced rainfall and more moderate soil temperatures of western Nebraska than in the greater rainfall and more fluctuating soil temperatures of eastern Nebraska. The greatest seed survival among the 41 weed species was shown by common mullein, which had 95% germination after 17 yr of burial in western Nebraska. Decay rates of individual weed species in soil will be of most value to weed scientists, agriculturalists, and modelers evaluating past or designing future weed management systems.

Velvetleaf is difficult to control in corn and soybean and the seed can persist in soil for many years. Seven cultural and tillage practices were established in 1974 on a site heavily infested with velvetleaf to determine the time required to eradicate velvetleaf seed from the soil. A rapid decline in velvetleaf seed population in the top 23 cm of soil occurred during the first 5 yr of this study. In the fifth year, the chemical fallow and continuous alfalfa treatments had 37 and 56% of the original velvetleaf seed population remaining, respectively. In the 17th year, soils in these treatments that had received no tillage since study initiation still contained 15 and 25% of the original velvetleaf seed population, respectively. Systems involving moldboard plowing with continuous-tillage fallow, continuous cropping of corn or oat, or an annual corn and soybean rotation had a more rapid decline in the velvetleaf seed population in soil compared to the chemical fallow and continuous alfalfa treatment. After 17 yr, soil in any system that had received at least one moldboard plowing per year still contained 1 to 3 million velvetleaf seed ha−1, which is only 0.8 to 2.5% of the initial viable seed population. Nearly 100% of the seed remaining in the soil in the 17th year for all treatments was still viable.

The distribution of sicklepod (Cassia obtusifolia L.) and coffee senna (Cassia occidentalis L.) in the United States is similar and both species are increasing as problems within their range. Sicklepod is a problem in 11 southern states and increasing in 12 while coffee senna is a problem in 7 states and increasing in 8 states. Both species germinated over a wide range of temperature. Germination characteristics were similar in the range of 15 to 36 C. Germination of coffee senna was drastically reduced at 39 C by Rhizopus sp. Seedling growth was similar for both species and was maximum from 30 to 36 C. Both species have a hard seedcoat. Abrasion for 5, 10, or 15 s, puncturing with a needle, and sulfuric acid were all effective in initiating germination. Both species emerged from a soil depth of 12.5 cm; however, emergence of sicklepod was more rapid than coffee senna with 63% of the sicklepod seedlings emerging from 2.5 cm after only 3 days.

A field experiment involving seven cultural practices was begun in 1974 in an area heavily infested with velvetleaf (Abutilon theophrasti Medic.) seed. Our objective was to determine the time required to eradicate velvetleaf seed from the soil. This paper reports the results of the first 4 yr of a long-term study. A cultural practice is repeated on the same plot year after year. Since the experiment was begun, no velvetleaf plants have been allowed to produce seed in any plots. The number of viable velvetleaf seeds is monitored by yearly soil sampling. In 1978, after 4 yr of a fallow treatment involving intensive tillage (two plowings per yr plus monthly tillage throughout the growing season), only 10% of the original seed population remained. However, that 10% was 1,300 viable seeds per m2 (to a depth of 23 cm). Four other practices that involved tillage gave generally similar results. Under undisturbed, continuous alfalfa, 56% of the original seed population remained after 4 yr, and under undisturbed, continuous chemical fallow, 37% remained. The results thus far demonstrate the extreme difficulty of eradicating velvetleaf seeds from the soil, and generally agree with reports in the literature, which primarily include studies conducted under more artificial conditions than we used. Our results also suggest that, in soil, velvetleaf seeds that have become water permeable (nonhard) may later again become water impermeable (hard).

Primary physical dormancy caused by seed coat impermeability to water is a major reason for the persistence of velvetleaf in soil seedbanks. Understanding temporal trends in seed dormancy status will help predict potential emergence in the spring. Experiments were begun in 1992 and 1993 to determine the effects of velvetleaf seed maturation time, storage environment, and storage duration on changes in seed dormancy and germination over 20 mo. Seeds buried 1 and 10 cm deep exhibited a 30 to 70% decline in physical dormancy from maturity until winter, little change in dormancy from winter through the following summer, and a further decline the next autumn. The loss of physical dormancy was more rapid for early than for late maturing seeds and more rapid in 1992 than in 1993. Physical dormancy of seeds held at 4 C declined steadily, at a rate of approximately 0.8% per day, over the course of the study. Germination of seeds buried 1 cm averaged 23 to 37% in the first spring after harvest, which was equivalent to 68 to 100% of seeds that had lost physical dormancy over autumn and winter. The percentage of seeds with enforced dormancy reflected the loss of physical dormancy during autumn and the loss of seeds to germination during spring and summer. Additional information on how autumn temperature and moisture conditions influence the pattern of dormancy decline could aid in explaining the variation in velvetleaf infestations over time.

The seed coat of Trifolium repens L. was studied with special emphasis on the development of the strophiole, which is the site for water entry during imbibition in leguminous seeds. The epidermal cells of the strophiole are longer than the cells in the remainder of the seed epidermis in the mature ovule. During seed development the median cells of the strophiolar epidermis divide periclinally into an outer layer of palisade cells and an inner layer of isodiametric cells. Prior to maturity a fissure is formed between some of the palisade cells in the centre of the strophiole. It is suggested that tension develops between the palisade cells and the iso-diametrical cells during later maturation stages causing the formation of the fissure which it is believed functions in water uptake. It is indicated that the ‘light line’ is caused by alteration of cellulose microfibrillar orientation in palisade cell walls. It is confirmed that removal of the epicuticular wax from hard seeds by rinsing in absolute alcohol or hexane does not induce water imbibition. Only when seed coats are mechanically abraded do hard seeds germinate.