The ability of orthodox seeds to survive long-term dry storage is a key prerequisite for ex situ seed conservation in genebanks. However, only a few credible observations of seed survival for ≥ 200 years have been reported. In this paper, seed survival is shown for three species under suboptimal storage conditions for a documented time of ≥ 203 years and carbon dated at 218–270 years. Two species that germinated are in the Fabaceae (Liparia sp. and Acacia sp.). A water-impermeable seed coat, and hence an inability to equilibrate with ambient relative humidity, may contribute to long-term survival of these species. The third species that germinated (Leucospermum sp.) does not have a water-impermeable seed coat, and long-term survival may be linked to an oxygen-impermeable barrier in the seed. These results for species from the Cape Floristic Region, South Africa, suggest adaptation for extreme longevity in seeds of species of seasonally dry, Mediterranean environments.

In the work reported in this paper, we attempted to elucidate the nature of the different abscisic acid (ABA) sensitivities presented by developing embryos from sorghum [Sorghum bicolor (L.) Moench] lines with contrasting pre-harvest sprouting (PHS) behaviour (Redland B2, susceptible; IS 9530, resistant). We explored two different hypotheses for a possible mechanism: (1) a different functionality of the ABA signalling pathway, and (2) a different rate of ABA degradation/conjugation in the apoplast of embryos from these genotypes. To assess the first possibility, we used an ABA-responsive gene (Rab17) as a reporter of changes in endogenous ABA content, which were artificially induced in embryos from both genotypes by means of fluridone application immediately after anthesis, to reduce ABA content, and embryo incubation in the presence of ABA. A defect in ABA signalling should be seen as a level of Rab17 expression that is independent of endogenous ABA content. For testing the second possibility at two stages of development, embryos from both lines were isolated and incubated in water for different periods. ABA concentrations in embryos and the incubation media were quantified through radioimmunoassay. In contrast to our findings for the resistant IS 9530 line, Rab17 expression did not respond to changes in ABA levels in sensitive Redland B2 embryos. The ABA degradation/conjugation rates in embryos and incubation media did not show clear differences between sorghum lines for any of the developmental stages analysed. These results suggest that a disruption in the ABA signal transduction pathway in Redland B2 underlies the low ABA sensitivity shown by embryos from this line.

In this study, we characterized two sunflower (Helianthus annuus L.) lines with differential sensitivity to drought, the sensitive line B59 and the tolerant line B71. Using both lines, we compared the content of endogenous jasmonates (JAs) in dry and imbibed seeds from plants grown under irrigation and drought. Jasmonic acid (JA), 12-oxo-phytodienoic acid (OPDA), 11-hydroxyjasmonate (11-OH-JA) and 12-hydroxyjasmonate (12-OH-JA) were detected in dry and imbibed sunflower seeds. Seeds from plants grown under drought had a lower content of total JAs and exhibited higher germination percentages than seeds from irrigated plants, demonstrating that environmental conditions have a strong influence on the progeny. OPDA and 12-OH-JA were the main compounds found in dry seeds of both lines. Imbibed seeds showed an enhanced amount of total JAs with respect to dry seeds produced by plants grown in both soil moisture conditions. Imbibition triggered a dramatic OPDA increase in the embryo, suggesting a role of this compound in germination. We conclude that JAs patterns vary during sunflower germination and that the environmental conditions experienced by the mother plant modify the hormonal content of the seed progeny.

We studied seasonal variation in density and species richness of seeds in the 0–10 cm soil depth layer in primary, secondary and pine forests, and in shrubland and grassland in the Shilin Stone Forest Geographical Park, Yunnan, SW China. Soil samples were collected four times during the year at 3-month intervals. Seeds from 119 species were identified by germination tests in the soil samples. Density and species richness of seeds of herbaceous plants were greater than woody plants at all five sites throughout the year. Sampling time and site differences had significant effects on the mean number of species and on seed-bank density. Mean number of species per sample increased from February, reached the highest value in May, decreased to the lowest value in August and then increased in November. An exception was in the primary forest, where the highest number of species was found in February. Mean seed-bank density peaked in May at all five sites, and no significant differences were found between densities in February, November and August, except for the primary forest. The peak in seed-bank density in May might be due to dispersal of new seeds of spring-fruiting species, combined with persistence of seeds dispersed in previous years. This seasonal variation of individual species was due primarily to differences in species phenology rather than to differences between sites. Four seasonal seed-bank strategies were identified: two transient and two persistent. At all sites, similar numbers of seeds of herbaceous species were found between seasons, but the number of species of trees and shrubs decreased in August.

Morphological traits of diaspores that can predict their potential attachment to animal coats may help to model epizoochory in plant populations and communities. The present study tested the role of seed mass, shape and the presence of dispersal structures in the attachment potential of a sample of 14 abundant species in Mediterranean grassland and shrubland, using sheep and cattle coats that were shaken mechanically using a standardized protocol. We also tested recently proposed predictive models for the attachment potential of diaspores. Attachment potential measured on cattle hide was low in comparison with sheep wool for all types of diaspores. Differences between vertically and horizontally positioned coats were significant only for cattle, in which attachment potential was higher in vertically positioned coats. Seed weight was highly significant to predict attachment potential in sheep coats, but yielded significant results only in the case of vertically positioned cattle coats. In both cases, light seeds were best retained. Shape yielded marginally significant results only in the case of horizontally positioned cattle coats. In this case, elongated seeds seemed to be best retained. The presence of appendages in diaspores was significant only for sheep, in which attachment potential was higher for seeds with appendages. Recently proposed predictive models for the attachment potential were found to be highly robust for predicting this parameter in sheep coats, and thus support their generalization for this type of coat.

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.

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%.