Anatomical and morphological seed traits are of great ecological importance and are a main subject of, for example, seed bank or endozoochory studies. However, we observed a lack of information about the relationship between seed anatomy and seed morphology and its ecological implications. To fill this gap, we linked the anatomical features of diaspore coverings to morphological characteristics of free seeds and one-seeded fruits. We predicted that: (1) the thickness and anatomical complexity of seed coat and pericarp are related to diaspore size and shape; and (2) the presence or absence of the pericarp may influence seed-coat thickness and anatomy. In our study we investigated diaspores of 39 central-eastern European herbaceous species and recorded the thickness and anatomical complexity of their seed coverings, and we determined diaspore mass and shape. Our results indicate that diaspore mass is positively related to covering thickness, lignification degree and anatomical complexity. This might be the case because bigger diaspores tend to remain on the soil surface and are more exposed to predation risk and environmental threat than smaller diaspores. Furthermore, more round-shaped diaspores had disproportionately thicker and more lignified coverings than long or flat ones, probably because round-shaped diaspores much more frequently form seed banks and therefore persist for a long time in the soil. We also found that free seeds as diaspores have a thicker and more lignified seed coat than seeds enclosed in fruits. In one-seeded fruits, the pericarp ‘takes the protective role’, it is thick, and the seed coat is poorly developed.

The seeds of Schinus molle are referred to as displaying physical dormancy because of their water-impermeable endocarp. Therefore, this work aimed to evaluate the germination of S. molle seeds as related to environmental conditions, scarification, storage time and seed anatomy. Various experiments were conducted to test the alleviation of dormancy in newly collected and stored seeds. Acid-scarified seeds incubated under continuous light at 25°C showed greatest vigour and germination. The separation of seeds by specific gravity revealed a higher germination percentage for those seeds that sank. In addition, dry storage alleviated dormancy with a remarkable increase in the various germination parameters. Overall, germination traits decreased after prolonged storage, but even after 12 months the means for germination parameters for stored seeds were still higher than those of newly collected ones. S. molle seeds remain attached to parts of the fruit mesocarp and endocarp. The mesocarp contains several layers of parenchyma showing secretory cavities. The endocarp consists of three layers of sclereids surrounding the embryo. Acid scarification strongly changed the structure of the external layers in the mesocarp, digesting parenchyma cells and removing the contents from both parenchyma cells and the secretory cavities; this improved water uptake during imbibition, which occurred only at the carpellary hilar slit. In conclusion, S. molle seeds are positively photoblastic and show physiological dormancy which can be alleviated by acid scarification and dry storage. Seeds can be stored for over 12 months without significant losses in germination parameters compared to newly collected seeds.

Does seed dormancy allow disturbance-oriented forest herbs such as Ageratina altissima to persist in heterogeneous natural communities? To document seed longevity and dormancy state, Ageratina seeds were buried in nylon mesh bags in second-growth forest stands in south-eastern Ohio, USA. Bags were recovered at 2-month intervals, and seeds were tested for viability and germinability in the lab. Live seed numbers declined rapidly, with seed banks exhausted in an estimated 33–37 months. Seeds showed a strong dormancy polymorphism, with 71–84% of live seeds germinable between March and July, the season of natural seedling emergence. At other dates, most seeds appeared to be in a state of induced dormancy, allowing little (0–21%) germination. The slope aspect of the burial site, an important factor controlling above-ground vegetation, had no effect on seed longevity or dormancy condition. Dormancy in Ageratina appears to be adapted to allow opportunistic germination in late spring–early summer, but to prevent germination in less benign periods. Seed longevity is shorter than the natural frequency of gaps in mesophytic forest. We conclude that a long-term dispersal/dormancy trade-off is probably an oversimplification of the spatial ecology of this species. The primary function of dormancy appears to be short-term tracking of seasonal variation.

Poor wheat seed quality in temperate regions is often ascribed to wet production environments. We investigated the possible effect of simulated rain during seed development and maturation on seed longevity in wheat (Triticum aestivum L.) cv. Tybalt grown in the field (2008, 2009) or a polythene tunnel house (2010). To mimic rain, the seed crops were wetted from above with the equivalent of 30 mm (2008, 2009) or 25 mm rainfall (2010) at different stages of seed development and maturation (17–58 DAA, days after 50% anthesis), samples were harvested serially, and subsequent air-dry seed longevity estimated. No pre-harvest sprouting occurred. Seed longevity (p50, 50% survival period in experimental hermetic storage at 40°C with c. 15% moisture content) in field-grown controls increased during seed development and maturation, attaining maxima at 37 (2008) or 44 DAA (2009); it declined thereafter. Immediate effects of simulated rain at 17–58 DAA in field studies (2008, 2009) on subsequent seed longevity were negative but small, e.g. a 1–4 d delay in seed quality improvement for treatments early in development, but with no damage detected at final harvests. In rainfall-protected conditions (2010), simulated rain close to harvest maturity (55–56 DAA) reduced longevity immediately and substantially, with greater damage from two sequential days of wetting than one; again, later harvests provided evidence of recovery in subsequent longevity. In the absence of pre-harvest sprouting, the potentially deleterious effects of rainfall to wheat seed crops on subsequent seed longevity may be reversible in full or in part.

Desert plants are exposed to water shortage and often salinity, instantly after dormancy withdrawal. We studied the effects of aridity and salinity on germination and initial growth of Bassiaindica, B. iranica and B. prostrata. We hypothesized that: (1) all species would exhibit adaptations to water shortage immediately after germination, including rapid root growth and high seedling-survival rates; and (2) obligate halophytes benefit from positive effects of salinity on germination success and desiccation tolerance. After we germinated seeds in water or NaCl solutions, desiccated and rehydrated them, we found that all three species showed rapid germination and root elongation, as well as good germination success. However, salinity had a negative effect on the germination success of all three, with only B. indica germinating in 3% NaCl. Salinity had a positive effect on desiccation tolerance of B. indica seedlings, but had no significant effect on either B. prostrata or B. iranica. Thus the presence of salinity immediately after germination can protect halophyte seedlings from desiccation. To the best of our knowledge, survival of seedlings after periods of desiccation and rewetting with solutions of up to 3% NaCl has never been reported. Studying salinity tolerance in halophytes is important in a world exposed to expanding desertification.

The fruit plus accessory parts, and thus not only the fruit or seed, is the diaspore in some species of flowering plants. Atriplex centralasiatica, a summer annual salt-secreting cold-desert halophyte of central Asia that produces flat and humped diaspores, is such a species. The dispersal/germination units of this diaspore-heteromorphic species are fruits enclosed in persistent ‘bracteoles’. Germination of black and brown fruits (i.e. ‘bracteoles’ removed) of this species has been studied in some detail previously, but little attention has been given to the germination biology of the intact diaspores. The aim of this study was to compare the germination biology of the intact diaspores of A. centralasiatica, and their fates in the field during 12 months on the soil surface and buried at 5-cm depth. Fresh flat diaspores germinated to 42.7–51.3% in light (12-h photoperiod) and to 16.0–59.3% in constant dark, over a temperature range of 15–20/30°C, while no freshly matured humped diaspores did so under any temperature/light regime. Neither gibberellin (GA3) nor potassium nitrate (KNO3) had an effect on germination of either diaspore. Both diaspores readily imbibed water, and removal of ‘bracteoles’ released most of the dormancy. Thus, the ‘bracteoles’ are primarily responsible for diaspore dormancy in A. centralasiatica. Humped diaspores persisted for a longer period in the soil than flat ones. The germination requirements of intact natural dispersal/germination units of A. centralasiatica differ from those previously reported for fruits of this species.

A climate warming of 2–5°C by the end of the century will impact the likelihood of seed germination of sugar maple (Acer saccharum), a dominant tree species which possesses a restricted temperature range to ensure successful reproduction. We hypothesize that seed origin affects germination due to the species' local adaptation to temperature. We tested this by experimentally investigating the effect of incubation temperature and temperature shifting on sugar maple seed germination from seven different seed sources representing the current species range. Survival analysis showed that seeds from the northern range had the highest germination percentage, while the southern range had the lowest. The mean germination percentage under constant temperatures was best when temperatures were ≤5°C, whereas germination percentages plummeted at temperatures ≥11°C (5.8%). Cool shifting increased germination by 19.1% over constant temperature treatments and by 29.3% over warm shifting treatments. Both shifting treatments caused earlier germination relative to the constant temperature treatments. A climate warming of up to +5°C is shown to severely reduce germination of seeds from the southern range. However, under a more pronounced warming of 7°C, seed germination at the northern range become more affected and now comparable to those found from the southern range. This study states that the high seed germination percentage found in sugar maple at the northern range makes it fairly resilient to the warmest projected temperature increase for the next century. These findings provide forest managers with the necessary information to make accurate projections when considering strategies for future regeneration while also considering climate warming.

Little information is available on seed dormancy of members of the Zingiberales and especially the Zingiberaceae. Our aim was to investigate the dormancy breaking and germination requirements of Alpinia galanga in vitro with a minimum number of seeds, using the move-along experiment. The mass of imbibed seeds increased by 17.5% in 1 d, showing that seeds were water permeable. The best germination in the move-along experiment (86.7%) was obtained when seeds were exposed to the sequence of temperature regimes that began with winter (20/10°C), and seeds began to germinate after 6 weeks at this temperature regime. Seeds dry stored for 4 months and then incubated at the sequence of temperature regimes that began with summer (30/20°C) started germinating in the sixth week at this temperature regime and had germinated to 93.3% after 18 weeks. Seeds kept dry for 4 months and then treated with 50 mg l−1 gibberellic acid (GA3) began to germinate at 30/20°C after 2 weeks. Control seeds incubated continuously at 20/10, 25/15 or 30/20°C germinated to 80.6, 77.8 and 60.0%, respectively. When incubated at 15, 20, 25 or 30°C, the ideal temperature for embryo growth was 20°C. Since GA3 and dry storage can break non-deep physiological dormancy and embryos grew during warm stratification, seeds of A. galanga have non-deep simple morphophysiological dormancy (MPD). This is the first report of non-deep simple MPD in the Zingiberaceae.

Orchid seeds are among the smallest seeds in nature and they are naturally rich in fatty acids. However, the fatty acid composition of orchid seeds has not been investigated because the sample masses utilized for widely used methods for fatty acid profiling would generally require prohibitively large numbers (i.e. 10,000s) of seeds. The present work aimed to develop a method for fatty acid analysis using gas chromatography–mass spectrometry on small quantities (mg) of seeds. The method was developed using the seeds of two species, Dactylorhiza fuchsii, a temperate terrestrial, and Grammatophyllum speciosum, a tropical epiphyte. A range of sample masses was tested to determine the minimum mass required to achieve reliable fatty acid composition data. A direct transesterification method was used, which did not require extraction of fatty acids from seeds prior to analysis, and the effects of seed processing (crushed versus intact seeds) and incubation time in toluene on fatty acid yield were tested. Stable fatty acid profiles were obtained using as little as 10 mg of seeds. Neither crushing the seeds nor extending the toluene incubation step had much effect on the fatty acid yield. The simple direct transesterification method presented will enable the fatty acid composition of orchid seeds, and possibly other small seeds, to be determined reliably for studies into seed development, storage and germination.

To increase our knowledge of the diversity of seed dormancy and germination in Rubiaceae, we investigated seed desiccation sensitivity and germination of three Psychotria species. Seeds of P. gardneri, P. nigra and P. zeylanica germinated to high percentages at <15% seed moisture content. Intact seeds of P. zeylanica and P. nigra imbibed water and thus do not have physical dormancy. More than 50% of the seeds of P. zeylanica, P. nigra and P. gardneri took 33, 53 and 110 d, respectively, at 25°C for the radicle to emerge, and embryo growth occurred before and after radicle emergence. Thus, seeds have morphophysiological dormancy. Shoot emergence of P. nigra and P. zeylanica seeds was delayed 50 and 80 d after radical emergence, respectively; thus, seeds have epicotyl morphophysiological dormancy (eMPD). This is the first report of eMPD in Rubiaceae. Since warm stratification promoted both radicle and shoot emergence in seeds of P. zeylanica and P. nigra, the level of eMPD is non-deep simple. Hence, dormancy of the studied Psychotria spp. can be described as C1bBb (radicle)–C1bBb (epicotyl), i.e. the embryo is underdeveloped and grows prior to radicle emergence and epicotyl emergence under warm temperatures (Bb), and both the radicle and epicotyl have non-deep simple physiological dormancy broken by warm temperatures (C1b). In two Psychotria species studied in detail, radicle emergence occurs at the beginning of the rainy season and plumule emergence at the peak rainy season when conditions are most favourable for rapid seedling development.

Group-testing regression methods are effective for estimating and classifying binary responses and can substantially reduce the number of required diagnostic tests. However, there is no appropriate methodology when the sampling process is complex and informative. In these cases, researchers often ignore stratification and weights that can severely bias the estimates of the population parameters. In this paper, we develop group-testing regression models for analysing two-stage surveys with unequal selection probabilities and informative sampling. Weights are incorporated into the likelihood function using the pseudo-likelihood approach. A simulation study demonstrates that the proposed model reduces the bias in estimation considerably compared to other methods that ignore the weights. Finally, we apply the model for estimating the presence of transgenic corn in Mexico and we give the SAS code used for the analysis.