Seeds of legumes are generally considered to have physical dormancy and to be orthodox, but most seed biologists are unaware of the various kinds and combinations of dormancy and storage behaviour in seeds of this family. The aim of our study was to document the dormancy and storage behaviour of seeds of 100 native and introduced tropical Fabaceae species in Sri Lanka and classify them into germination/storage behaviour categories. Moisture content (MC) was < 16% for fresh seeds of 94 species and >29% for those of six. Seeds of these six species had low tolerance for desiccation and for low temperatures. Thus, seeds of six species are non-orthodox and 94 species orthodox. Nine of the 100 species were non-dormant, and 2, 3 and 86 had physiological, physiological epicotyl and physical dormancy, respectively. Six germination/storage behaviour categories were identified among the 100 species. However, as in extratropical regions of the world, orthodox storage behaviour and physical dormancy are characteristic of seeds of the majority of species of Fabaceae in tropical Sri Lanka.

The interaction between ethylene production and seed germination of sugar beet (Beta vulgaris L.) was studied. For intact fruits, deoperculated fruits and true seeds, ethylene was only produced after the start of radicle emergence. Removal of the operculum or the whole pericarp, likely allowing better water uptake and gas exchange by the true seed, actually increased the time span between the start of radicle emergence and the beginning of ethylene production compared to intact fruits. ACC (1-aminocyclopropane-1-carboxylic acid), AOA (aminooxyacetic acid), AIB (2-amino isobutyric acid) and STS (silver thiosulphate) in the imbibition medium did not influence the germination pattern. Based on these findings, the function of ethylene during the germination of sugar beet is uncertain.

Temperature and water potential strongly influence seed dormancy status and germination of Bromus tectorum. As seeds of this plant can be killed by the ascomycete fungus Pyrenophora semeniperda, this study was conducted to learn how water potential and temperature influence mortality levels in this pathosystem. Separate experiments were conducted to determine: (1) if P. semeniperda can kill dormant or non-dormant seeds across a range of water potentials (0 to − 2 MPa) at constant temperature (20°C); and (2) how temperature (5–20°C) and duration at reduced water potentials (0–28 days) affect the outcome. When inoculated with the fungus at 20°C, all dormant seeds were killed, but fungal stromata appeared more quickly at higher water potentials. For non-dormant seeds, decreasing water potentials led to reduced germination and greater seed mortality. Results were similar at 10 and 15°C. Incubation at 5°C prevented stromatal development on both non-dormant and dormant seeds regardless of water potential, but when seeds were transferred to 20°C, dormant seeds evidenced high mortality. For non-dormant seeds, exposure to low water potential at 5°C resulted in secondary dormancy and increased seed mortality. Increasing incubation temperature, decreasing water potential and increasing duration at negative water potentials all led to increased mortality for non-dormant seeds. The results are consistent with field observations that pathogen-caused mortality is greatest when dormant seeds imbibe, or when non-dormant seeds experience prolonged or repeated exposure to low water potentials. We propose a conceptual model to explain the annual cycle of interaction in the Bromus tectorum–Pyrenophora semeniperda pathosystem.

Although seed dormancy of temperate legumes is well understood, less is known about it in species that grow in subalpine/alpine areas. This study investigated dormancy and germination of four Vicia species from the Tibetan Plateau. Fresh seeds of V. sativa were permeable to water, whereas those of V. angustifolia, V. amoena and V. unijuga had physical dormancy (PY). One year of dry storage increased the proportion of impermeable seeds in V. angustifolia, but showed no effect on seed coat permeability in V. amoena or V. unijuga. Seeds of all four species also had non-deep physiological dormancy (PD), which was especially apparent in the two annuals at a high germination temperature (20°C). After 1 year of storage, PD had been lost. The hydrotime model showed that fresh seeds obtained a significantly higher median water potential [Ψb(50)] than stored seeds, implying that PD prevents germination in winter for seeds dispersed without PY when water availability is limited. After 6 months on the soil surface in the field, a high proportion of permeable seeds remained ungerminated, further suggesting that PD plays a key role in preventing germination after dispersal. Addition of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis, evened-out the differences in germination between fresh and stored seeds, which points to the key role of ABA biosynthesis in maintaining dormancy. Further, fresh seeds were more sensitive to exogenous ABA than stored seeds, indicating that storage decreased embryo sensitivity to ABA. On the other hand, the gibberellic acid GA3 increased germination rate, which implies that embryo sensitivity to GA is also involved in seed dormancy regulation. This study showed that PY, PD or their combination (PY+PD) plays a key role in timing germination after dispersal, and that different intensities of dormancy occur among these four Vicia species from the Tibetan Plateau.

Testing for the unintended or adventitious presence (AP) of genetically modified (GM) events in seed lots is a common practice to comply with regulatory requirements and good stewardship practices. A subsample of a seed lot is typically tested for AP levels, and then statistical methods are used to estimate the upper level of AP in the remainder of the lot with a given level of confidence. For large seed lots, a binomial distribution is typically assumed, but for seed lots where the tested sample is a substantial proportion of the overall seed lot, a hypergeometric distribution is typically assumed. Due to the destructive nature of AP seed testing, we suggest that this latter method may overestimate confidence of low AP in the remaining seed.

Spinach (Spinacia oleracea L.) seed quality is important for subsequent establishment of baby leaf and other spinach products. The indeterminate flowering pattern in spinach produces seeds of different sizes, and consequently a non-uniform seed lot. Sorting seeds based on novel sorting methods might therefore improve the establishment of spinach for producers. Spinach seeds were harvested at five different times (H1, H2, H3, H4 and H5) starting 3 weeks before estimated optimum harvest time. The harvested seeds were sorted according to chlorophyll fluorescence (CF) and seed size. Two harvest times 6 d apart were selected for further studies of seed development and germination counts. Analysis of mean germination time (MGT) of four germination counts (3, 7, 14 and 21 d) showed that smaller seed sizes ( < 3.25 mm) have lower MGT than seeds of larger sizes (>3.25 mm). A larger proportion of 2.5–3.25 mm size seeds had germinated on day 3 than both their larger and smaller counterparts at the later time of harvest (H4). Seeds with a diameter below 2.5 mm displayed the lowest MGT. Commercially, the use of chlorophyll fluorescence (CF)-sorted seeds, in combination with seed size sorting, may provide a useful tool for enhancing seed quality. Here our results demonstrate that a greater number of seeds with a low CF level had germinated on day 3 compared to the seeds with high CF levels. It is of relevance to develop a technology that could identify seeds that are sufficiently developed to germinate and successfully establish in the field regardless of seed size.

Narcissus longispathus (Amaryllidaceae) is a perennial geophyte and a Mediterranean narrowly endemic species. At dispersal time, N. longispathus seeds are dormant and have underdeveloped embryos. This work aimed to determine requirements for dormancy break and germination and to compare dormancy traits with those of the two endemic Iberian congeners. Phenology of embryo growth and germination were studied by regularly exhuming seeds sown in near-natural conditions. Temperature and light requirements for embryo growth, breaking of dormancy and germination were determined by incubating seeds under controlled laboratory conditions. Mean embryo length in fresh seeds was 1.50 mm, and embryos had to grow to 3.80 mm before radicle emergence. Embryos grew to full size and seeds germinated when they were warm stratified for 2 months (optimum 1 month at 20/7°C+1 month at 15/4°C), then cold stratified at 5°C for 2 months, and finally incubated at cool temperatures (15/4°C) for 30 d. However, in seeds only subjected to either warm or cold stratification, the embryos hardly grew and did not germinate. In natural conditions, the embryos elongate in autumn–winter, and in late winter–early spring (March) almost all radicles and seedlings emerged. Velocity of embryo growth and germination percentages increased with seed storage duration. Seeds of N. longispathus have non-deep complex morphophysiological dormancy (MPD). This is the first report of such a level of MPD in Narcissus. Our data suggest that non-deep complex MPD may have been derived from intermediate complex MPD in the section Pseudonarcissi.

The present work aims to determine whether there are patterns of seed and germination characteristics in Vellozia due to the phylogenetic proximity among the species examined and if these characteristics explain their restricted geographical distributions. We evaluated the germination characteristics of freshly collected seeds from 13 species of the genus Vellozia (Velloziaceae) that show different degrees of endemism, collected at various locations in the Espinhaço Mountain Range in Minas Gerais State, south-eastern Brazil. The size and mass of the seeds, as well as the influence of light and temperature on their germination, were measured. Experiments were performed in germination chambers under constant temperatures of 10–40°C (intervals of 5°C), with a 12-h photoperiod, as well as in continuous darkness. All species studied had small seeds with mass varying from 0.06 to 1.21 mg. Most species required light for germination, displaying high germinability in the range of 15–40°C; some species, however, germinated in the absence of light at the highest temperatures (35 and 40°C). The sizes and masses of the seeds showed significant linear correlations, but light sensitivity was not related to these seed characteristics. The responses observed suggest that light requirement for germination, associated with the small sizes of Vellozia spp. seeds, contribute to the formation of persistent seed banks. The observed tolerance of these seeds to a wide range of germination temperatures is consistent with the large daily temperature fluctuations experienced in campos rupestres sites, although these seed characteristics cannot by themselves explain the high degree of endemism or the restricted distributions observed among the species examined.

Although it has been speculated that seeds of the gymnosperm family Podocarpaceae have an underdeveloped embryo, no detailed studies have been done to definitively answer this question. Our purpose was to determine if embryos in seeds of two species of Podocarpaceae, Podocarpus costalis and Nageia nagi, from Taiwan are underdeveloped and to examine the kind of dormancy the seeds have. Embryos in fresh seeds of P. costalis were 4.6 ± 0.5 mm long, and they increased in length by about 54% before radicle emergence (germination), demonstrating that the embryo is underdeveloped at seed maturity. Seeds germinated to >90% at 30/20, 25/15 and 25°C in light in ≤ 4 weeks, without any cold stratification pretreatment. Thus, seeds of P. costalis have morphological dormancy (MD). Embryos in fresh seeds of N. nagi were 7.4 ± 0.8 mm long and they increased in length by about 39% before radicle emergence (germination) occurred, indicating that the embryo is underdeveloped at seed maturity. Seeds germinated to < 25% at 30/20 and 25°C in light in 4 weeks but to >90% at the same temperatures in 12 weeks. Thus, most seeds of N. nagi have morphophysiological dormancy (MPD). Although underdeveloped embryos are considered to be a primitive condition in seed plants, they also occur in the most advanced orders. The occurrence of underdeveloped embryos in Podocarpaceae documents that they are not restricted to a basal clade in gymnosperms.

Invasive alien plants often occur in monospecific stands with high density in the invaded range. Production of bioactive secondary metabolites in such stands could have allelopathic effects on germination of native species. We tested this component of the novel weapon hypothesis for Heracleum mantegazzianum, a prominent invader in Europe, using seeds of 11 native herbs exposed to soil or soil extracts from invaded stands, moist seeds or seed extracts of H. mantegazzianum. There was no effect of the various treatments on germination of most species, while germination was reduced in Urtica dioica on invaded soil, in Poa trivialis with H. mantegazzianum seed extract, and negative effects of the essential oil bergapten were found in three species. In P. trivialis the results of the seed extract were not supported by the experiment with added seeds of the invasive plant. Thus, there is limited evidence for allelopathic effects of the invasive H. mantegazzianum on germination of co-occurring native herbs.

In this study we developed a sample size procedure for estimating the proportion of genetically modified plants (adventitious presence of unwanted transgenic plants, AP) under inverse negative binomial group testing sampling, which guarantees that exactly r positive pools will be present in the sample. To achieve this aim, pools are drawn one by one until the sample contains r positive pools. The use of group testing produces significant savings because groups that contain several units (plants) are analysed without having to inspect individual plants. However, when using group testing we need to consider an appropriate pool size (k) because if the k individuals that form a pool are mixed and homogenized, the AP will be diluted. This effect increases with the size of the pool; it may also decrease the AP concentration in the pool below the laboratory test detection limit (d), thereby increasing the number of false negatives. The method proposed in this study determines the required sample size considering the dilution effect and guarantees narrow confidence intervals. In addition, we derived the maximum likelihood estimator of p and an exact confidence interval (CI) under negative binomial pool testing considering the detection limit of the laboratory test, d, and the concentration of AP per unit (c). Simulated data were created and tables presented showing different potential scenarios that a researcher may encounter. We also provide an R program that can be used to create other scenarios.