Rudimentary, broad and small linear embryos occur among members of the most primitive (basal) extant angiosperms, collectively called the ANITA grade (i.e. Amborella, Nymphaeales and Austrobaileyales). Amborella (rudimentary) and Austrobaileyales (rudimentary in Austrobaileyaceae, Illiciaceae and Schisandraceae and small linear in Trimeniaceae) have kinds of embryos that are known to be underdeveloped; consequently, they must grow inside the seed prior to radicle emergence (germination). On the other hand, it is not known if broad embryos need to grow before radicles can emerge, and whether they are underdeveloped or fully developed. Thus, we addressed the question: ‘Is the broad embryo of Nymphaeales also underdeveloped?’. Although the embryo length : seed length ratios in Nymphaea Albert Greenburg, N. capensis var. zanzibariensis and N. immutabilis were 0.311, 0.349 and 0.234, respectively, embryos did not grow prior to radicle emergence. Thus, they are fully developed at seed maturity. If Amborella and Nymphaeales are equally the most basal angiosperms, as some molecular phylogenetic studies indicate, then we must conclude that the broad and rudimentary embryos are equally primitive.

To obtain information on possible sources of contamination of the seed harvest of oilseed rape (Brassica napus L., spp. napus) by other varieties (adventitious presence), we investigated the purity of certified seed lots; the abundance and origin of volunteers; and longevity and origin of seeds in the soil seed-bank. This information was acquired through DNA analysis of volunteers collected in the field and seedlings derived from the soil seed-bank. DNA profiles of the volunteers and seedlings were obtained using Inter Simple Sequence Repeat (ISSR) markers, and the profiles were compared with ISSR profiles from an assortment of 14 of the most commonly cultivated oilseed rape varieties from 1985 to 2004. This comparison was performed using the assignment program, AFLPOP. The age of the seed bank germinating to become volunteers was assumed from information on previously cultivated oilseed rape varieties at the site and the year of cultivation. The results showed that plants or seeds belonged to varieties cultivated at the site 4–17 years earlier, suggesting a long persistence of volunteer populations. High volunteer frequencies (6%, 29% and 32%) were found in the three oilseed rape fields analysed and, from soil cores, their soil seed-bank was estimated to be 50–100 seeds m− 2. The ISSR analysis of the 14 reference varieties showed that three of the certified seed lots contained other varieties above the allowed threshold. Our findings are discussed in the context of the coexistence between GM (genetically modified) and non-GM oilseed rape, and future levels of seed purity.

The size and composition of the seed bank of a rare species (Erica ciliaris L.) was analysed. E. ciliaris hybridizes with a common relative in southern England (Erica tetralix). The seed banks of these co-occurring species were measured at a number of sites with a range of vegetation types and different management histories. Additional sets of samples were taken from forestry plantations on former heathland sites, where these species were known to occur. Relatively few hybrid seedlings were found in any of the seed-bank samples, even though their vegetative abundance within the sampling areas was equal to that of the pure plants. However, the abundance in the vegetation of the two pure species was reflected in the seed-bank size on each of the vegetation types, both with and without burning management. The seed banks from the forestry plantations show that the numbers of seeds of both E. tetralix and the hybrid were depleted, but that the seed bank of E. ciliaris was not significantly different from that of open heathland seed banks. The long-lived nature of the seed bank indicates that there are opportunities for habitat restoration on former heathland sites.

Substances that could play a role in maintaining seed viability (phenolic compounds, α-tocopherol, sterols, ascorbic acid, glutathione and soluble proteins) were estimated in beech (Fagus sylvatica L.) seed lots that had been stored for 2, 5, 7 and 10 years at − 10°C. Germination capacity was strongly and positively correlated with amounts of total phenolic compounds, ultraviolet (UV)-absorbing phenols and soluble proteins. Moderately strong relationships appeared between germination capacity and α-tocopherol and ascorbic acid contents. Total sterol and glutathione contents were not correlated with germination capacity. A strong, negative correlation was found between germination capacity and reactive oxygen species (ROS), such as superoxide radical () and hydrogen peroxide (H2O2), as well as with lipid hydroxyperoxides (LHPOs). The putative role of these compounds in the maintenance of beech seed viability during long-term storage is discussed.

LEAFY (LFY)-like proteins are plant-specific transcription factors that play essential roles in plant growth and development. In this study, a LEAFY homologue in soybean [Glycine max (L.) Merr.], designated as GmLFY, was cloned from inflorescences by the rapid amplification of cDNA ends (RACE) method. Sequence analysis showed that GmLFY cDNA contained a 1221 bp open reading frame, encoding 407 amino acid residues with typical characteristics of transcription factors. Subcellular localization in onion epidermal cells indicated that GmLFY protein was located in the nucleus. Analysis of the GmLFY genomic structure showed that the GmLFY gene has two introns with similar spliced sites as LFY-like genes in other plants. Reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that GmLFY was predominantly expressed in reproductive organs, such as inflorescences, pods and developing seeds. Further analysis showed that the expression level of GmLFY was higher in the middle stage than in the early or late stages of seed development, suggesting an essential regulatory role of GmLFY in soybean seed development.

The effect of flooding on the dormancy level of Setaria parviflora seeds from a non-flooded upland and a seasonally (winter–spring) flooded lowland in the Pampa grasslands of Argentina was investigated. Seeds from both communities were subjected to reciprocal burial treatments in the two habitats, and exhumed during and after the flooding season. Effect of immersion in water at 5°C was compared to incubation of seeds on the surface of water-saturated paper at the same temperature. After exhumation of the buried seeds or immersion treatments, germination was assayed at 25°C and at 20/30°C in the dark or in combination with light. Burial in the lowland, which was flooded in winter–spring, significantly reduced germination, while burial in the non-flooded upland did not reduce germination. Similarly, immersion in water at 5°C significantly reduced germination compared to non-immersed controls. During summer, seeds buried in the lowland showed increased capacity to germinate, particularly when exposed to fluctuating temperatures or light. Thus, flooding induced secondary dormancy in S. parviflora seeds, and it was broken during the non-flooding season. These responses of the seeds would prevent germination until there was no further risk of flooding. Remarkably, in S. parviflora seeds harvested from both habitats, we observed essentially the same germination requirements after flooding. However, some slight differences were detected between the seed populations exhumed from the lowland site, indicating that flooding had larger effects on the seeds from the upland community. This suggests some differentiation of these populations evident only after flooding in the field.

This is the first study to determine the class of seed dormancy (or non-dormancy) of a large number of native tree species in a tropical forest, the seasonal moist tropical forest of the Panama Canal Watershed (PCW), or to test the relationships between class of dormancy (or non-dormancy) and various seed and ecological characteristics of the constituent species. Fresh seeds of 49 of 94 tree species were non-dormant (ND), and 45 were dormant (D). Seeds of 23 species had physiological dormancy (PD), 13 physical dormancy (PY), two morphological dormancy (MD), 7 morphophysiological dormancy (MPD) and none combinational dormancy (PY+PD). Seeds with PY were significantly smaller ( < 0.1 g) and drier (moisture content < 16%) at maturity than those that were ND or in the other D classes. Seeds of 62, 42 and 53% of species dispersed in the early rainy, late rainy (LRS) and dry seasons, respectively, were ND. The majority (61%) of species with PD seeds, but only 17% of those with PY seeds, were dispersed in the LRS. The proportion of species with ND seeds was higher in large-size (63%) than in mid-size (35%) and understorey (17%) trees, but differed only slightly between non-pioneers (58%) and pioneers (54%). The proportion of species with D seeds increased only slightly through a precipitation gradient of about 3100 to 1900 mm in the PCW; however, PY increased from 19 to 32% and PD decreased from 63 to 44%.

Trials were carried out to investigate natural weed seed burial in a no-till agricultural system. With this aim, 30 important weed species were selected to explore if, and to what extent, seed vertical movement is conditioned by soil texture, cumulative rainfall or by seed characteristics. Without soil tillage, the vertical position of the seeds was only a few millimetres below the surface, but it was dependent on soil texture. Seed burial was much slower (and to lesser depths) in clay soils than in sandy soils. Seeds reached greater depths after 1 year in sandy soil (10% >6 mm) than in clay soils (2% >6 mm). Burial dynamics were also influenced by rainfall and seed weight. The amount of rain necessary to halve weed seeds observable on the soil surface was a function of the soil texture and seed weight; linear regressions between total rainfall amounts and seed weight showed that the slope of the relationship increased as the sand component of the soil decreased (21.1, 35.4 and 39.4 in sandy, loam and silty-clay soil, respectively). A polynomial regression, carried out in sandy soil, between 1000-seed weight and their burial capacity showed an inverse relation (P>0.05) between these two parameters. Seed shape and coat microsculpture also influenced movement, but only minimally.

Observing the embryo in dust-like seeds with a rigid coat presents a particular challenge, because it is not possible to use conventional techniques applied to normal-sized seeds. A new combination of softening and clearing techniques, which is remarkably effective for direct observations of embryos in minute seeds, is reported here. Moreover, no special seed treatment is required prior to application of this combination of techniques, and good results are obtained from living and preserved material. Dust-like seeds of Cytinus hypocistis and Cytinus ruber with a rigid coat were treated successively with Franklin's and with Jeffrey's softening fluids, and then with Herr's clearing fluid. The combined action of the two softening fluids caused sufficient seed coat rupture to allow Herr's fluid to clear seed tissues, permitting effective observation of the embryo. This technique should be applicable to a wide range of species with dust-like seeds, and its possibilities for biological studies are numerous.

Four temperature response models were compared describing the emergence rate of Solanum sisymbriifolium (L.) over a broad range of suboptimal temperatures and at different soil water potentials. In the laboratory, the effects were tested on germination rates at constant (9.1–21.8°C) and diurnally fluctuating temperatures at different soil water potentials. Linear, Q10, expolinear and quadratic models were fitted to the data on rate of emergence against temperature. For model validation, field emergence was monitored in 11 sowings conducted in 2001–2004. Emergence rate increased with temperature and was relatively high at soil water potentials in the range of − 0.21 MPa to − 2.6 × 10− 3 MPa, but was almost zero at − 0.96 MPa and − 1.8 × 10− 3 MPa. Diurnal temperature fluctuations did not have a differing influence on germination rates or final germination percentages compared with constant temperatures. The expolinear and the quadratic models were most accurate in explaining variation of laboratory data, especially at temperatures close to the minimum germination temperature of S. sisymbriifolium. These two models had root mean square errors for predicting field emergence rates (5.9 to 38.4 d) of 0.81 and 0.87 d, respectively, and were considered more appropriate to predict the time to 50% germination for crops grown in conditions near their ‘base temperature’ than the widely used linear temperature (thermal time) models. The Gompertz function was fitted to percentage germination versus the time-accumulated germination rate (using the expolinear function to describe the rate–temperature relation). This combined model adequately predicted the temporal pattern of emergence in the field.