Strigolactones are apocarotenoids regulating shoot branching. They are also known to be exuded by plant roots at very low concentrations, stimulating hyphal branching of arbuscular mycorrhizal fungi and germination of root parasitic weed seeds. We show that strigolactones play a major role in host specificity of Orobanche and Phelipanche (the broomrapes) seed germination. This observation confirms that host-derived germination stimulants are an important component determining the host specificity of these parasitic plants. Weedy broomrape species were less specialized in germination requirements than the non-weedy species except for O. cumana and O. foetida var. broteri. Similar results were obtained with the root exudates. Some species, such as P. aegyptiaca and O. minor, showed a broad spectrum of host specificity in terms of seed germination, which was stimulated by exudates from the majority of species tested, whereas others, such as O. cumana, O. hederae and O. densiflora, were highly specific. Some species, such as O. minor, P. aegyptiaca and P. nana, were responsive to the three strigolactones studied, whereas others were induced by only one of them, or did not respond to them at all. The synthetic strigolactone analogue GR24, generally used as a standard for germination tests, was not effective on some Orobanche and Phelipanche species. Seeds of some species that did not respond to GR24 were induced to germinate in the presence of fabacyl acetate or strigol, confirming the role of strigolactones in host specificity.

Fleshy fruits fall on to the ground together with cleaned seeds previously ingested by primary dispersers, offering a wide range of fruits and seeds to the ground foragers. Although nutritional properties strongly differ between fruits and seeds, this different seed presentation (cleaned seeds versus seeds within the pulp) has not been addressed in seed removal studies. This study reports on the removal of fruits versus their seeds in five fleshy-fruited species in a temperate forest. We found that rodents removed most of the seeds and partially consumed most of the fruits, preferring seeds to fruits. Rodents bit the fruits to extract the seeds, leaving most of the pulp. We found a preference ranking for the seeds (Sorbus aucuparia>Ilex aquifolium>Sorbus aria>Rosa canina>Crataegus monogyna) but no preferences were found for the fruits, probably due to their similarities in pulp constituents. Seed and fruit choice were affected by chemical and physical properties and not by their size. The presence of alternative and preferred seeds (nuts) delayed the encounter of the fruits and seeds and diminished their removal rates. We found that higher rodent abundance is not necessarily associated with higher removal rates of fleshy fruits. Rodent abundance, fruit size and seed size are minor factors in the removal of fleshy fruits and their seeds. This study underlines that scatter-hoarding rodents are important removers of fleshy fruits and their seeds, producing a differential seed removal depending on the seed presentation (with or without pulp), the nutritional properties of the seeds (but not of the fruits) and the presence of alternative food.

Restoration of semi-natural grassland communities involves a combination of (1) sward disturbance to create a temporal window for establishment, and (2) target species introduction, the latter usually by seed sowing. With great regularity, particular species establish only poorly. More reliable establishment could improve outcome of restoration projects and increase cost-effectiveness. We investigated the abiotic germination niche of ten poorly establishing calcareous grassland species by simultaneously exploring the effects of moisture and light availability and temperature fluctuation on percentage germination and speed of germination. We also investigated the effects of three different pre-treatments used to enhance seed germination – cold-stratification, osmotic priming and priming in combination with gibberellic acid (GA3) – and how these affected abiotic germination niches. Species varied markedly in width of abiotic germination niche, ranging from Carex flacca with very strict abiotic requirements, to several species reliably germinating across the whole range of abiotic conditions. Our results suggest pronounced differences between species in gap requirements for establishment. Germination was improved in most species by at least one pre-treatment. Evidence for positive effects of adding GA3 to seed priming solutions was limited. In several species, pre-treated seeds germinated under a wider range of abiotic conditions than untreated seeds. Improved knowledge of species-specific germination niches and the effects of seed pre-treatments may help to improve species establishment by sowing, and to identify species for which sowing at a later stage of restoration or introduction as small plants may represent a more viable strategy.

The distribution and dynamics of plant populations depend on the recruitment of young individuals, which is influenced by seed production, animal seed dispersal, dispersal distance, and the deposition of seeds in favourable places for seed germination/establishment and seedling survival. In particular, seeds dispersed over long distances will likely encounter new environmental conditions that occur at large spatial scales, with seed and seedling survival influenced by the adaptation of plant populations to soil and climate conditions. In this paper, it is hypothesized that seed germination and seedling survival probabilities depend on seed origin and deposition sites. A reciprocal seed and seedling transplant experiment was carried out with zapote seeds (Manilkara zapota) to determine the effect of origin and deposition sites on seed germination and seedling survival over a year in the Greater Calakmul Region of Mexico. Two origin and two deposition sites were selected that show different soil moisture levels within the habitat of the Baird's tapir, a major seed disperser of M. zapota seeds. The results show that sites of origin and deposition influenced seed germination and seedling survival probabilities. This suggests that the displacement of seeds far from parent trees, while potentially reducing intraspecific competition, does not ensure their survival, and that seeds need to be deposited in microsites within their environmental tolerance for dispersal to be successful. Furthermore, this paper emphasizes the importance of field experiments to provide strong inference about the effects of environmental conditions on recruitment and distribution of plant species.

Pre-harvest sprouting (PHS) is a serious risk when adapting quinoa (Chenopodium quinoa) seed production to different temperate environments. Two quinoa accessions, ‘2-Want’ and ‘Chadmo’ were evaluated under field conditions in the Argentinean pampas over 2 years on five different sowing dates, to explore a range of climate conditions under which seed filling is manageable in this region. Both accessions exhibited dormancy during seed development and maturation under the conditions examined; however, dormancy expression was restricted to low temperatures in 2-Want, while seeds of Chadmo, originating from the humid island of Chiloe, southern Chile, expressed a high level of dormancy at all examined temperatures. Dormancy release was observed as a reduction in the lowest temperature permissible for seed germination, which broadened the optimal germination temperature window. Higher storage temperature increased the rate of dormancy release. The environment during seed development on the mother plant affected the levels and patterns of seed dormancy, with higher temperatures and longer photoperiods promoting dormancy. As dormancy was released before the next production period, the levels of dormancy observed in the accession would allow timely planting and uniform germination, while dormancy during seed maturation ensures the prevention of PHS. Chadmo showed deeper dormancy levels in all situations, compared with 2-Want, therefore greater PHS tolerance under various conditions in the pampas region can be expected for Chadmo, which makes this accession a better candidate to be included in adaptive breeding programmes for quinoa.

Five Euphorbiaceae species (Jatropha macrocarpa, J. hieronymi, J. excisa, Cnidoscolus tubulosus and Manihot guaranitica) were analysed for seed oil content and fatty acid profiles in order to evaluate their potential as sources of biodiesel. The five species are perennial shrubs adapted to arid and semi-arid environments of north-western Argentina. The seed oil content for all species ranged from 27.9 to 38.7% by dry weight. Fatty acid composition consisted mainly of linolenic, myristic, palmitic, stearic, arachidic, oleic and linoleic acids, with linoleic and oleic acid being the most abundant. Among the five species analysed, J. macrocarpa has the best potential to be used as a biodiesel source. The average total seed oil content (35.8%) and a high value of oleic acid (27.3%) together with the lowest values of linoleic acid (55.8%) make this species a promising crop as a source of biodiesel in arid and semi-arid regions.

The detection and quantification of the prevalence of genetically modified organism (GM) contamination in seed exports is a critical element of regulatory compliance. While the procedures to reliably detect high levels of GM contamination are well understood, no comparable statistical approaches are available for the quantification of levels of GM prevalence below the established detection rate of standard tests. We present a simple statistical approach based on simulation modelling for the quantification of low levels of GM contamination. The approach can be modified to match any sampling regime and can account for rates of false positive and negative assay results. The application of this method is demonstrated using the low level of contamination in Canadian flax breeder seed lots by the GM flax variety ‘Triffid’. We show that GM contamination is likely present in seed lots at rates between two GM seeds per million and six seeds per hundred thousand. We also show that this low level of presumed contamination is indistinguishable from the number of positive tests expected from a clean seed lot given the potential rates of false positive tests.

Group testing is a procedure in which groups that contain several units (plants) are analysed without having to inspect individual plants, with the purpose of estimating the prevalence of genetically modified plants (adventitious presence of unwanted transgenic plants, AP) in a population at a low cost, without losing precision. When pool (group) testing is used to estimate the proportion of AP (p), there are several procedures that can be used for computing the confidence interval (CI); however, they usually do not ensure precision in the estimation of p. This research proposes a formula for determining the required number of pools (g), given a pool size (k), for estimating the proportion of AP plants using the Dorfman model. The proposed formula ensures precision in the estimated proportion of AP because it guarantees that the width (W) of the CI will be equal to, or narrower than, the desired width (ω), with a probability of γ. This probability accounts for the stochastic nature of the sample variance of p. We give examples to show how to use the proposed sample-size formula. Simulated data were created and tables are presented showing the different scenarios that a researcher may encounter. The Monte Carlo method was used to study the coverage and the level of assurance achieved by the proposed sample sizes. An R program that reproduces the results in the tables and makes it easy for the researcher to create other scenarios is given in the Appendix.

Seed dormancy and germination involve the concerted operation of molecular and biochemical programmes. It has become feasible to study these processes in great detail, using the current methods for transcriptome, proteome and metabolome analysis. Yet, the large amounts of data generated by these methods are often dazzling and demand efficient tools for data visualization. We have used the freely available PageMan/MapMan package (http://MapMan.gabipd.org) to visualize transcriptome and metabolome changes in Arabidopsis thaliana seeds during dormancy and germination. Using this package we developed two seed-specific MapMan pathways, which efficiently capture the most important molecular processes in seeds. The results demonstrated the usefulness of the PageMan/MapMan package for seed research.

Lipid peroxidation and membrane damage are often proposed as causes of recalcitrant seed death, and the thiobarbituric acid reactive substances (TBARS) assay is commonly used to measure lipid peroxidation. However, several artefacts can cause an overestimation of TBARS values, and these have not been routinely addressed in experiments with recalcitrant seeds. In the present report, TBARS was assayed as recalcitrant Spartina alterniflora and orthodox S. pectinata seeds were dried rapidly. Using the traditional Heath and Packer (1968) protocol with tissue extraction at 4°C, S. alterniflora had higher overall TBARS values than S. pectinata, and TBARS products increased when recalcitrant S. alterniflora and orthodox S. pectinata seeds were dried. However, when corrections for interfering substances, such as sugars and anthocyanins, were made, the TBARS values between the two species were almost identical. When seeds were freeze-clamped in liquid nitrogen prior to extraction, TBARS did not increase during desiccation for either species. These findings may indicate that lipid peroxidation is not the cause of desiccation-induced death in S. alterniflora. Therefore, freeze-clamping during tissue extraction and corrections for TBARS interfering substances must be applied to avoid overestimation of lipid peroxidation values.

Size-class structure was used to monitor the growth of underdeveloped embryos in two seed cohorts of Aristolochia macrophylla, A. tomentosa and A. californica and the results are related briefly to differences in seed dormancy among and within the three species. The size-class method of presenting embryo growth data allows more insight to be gained into the embryo-level cause(s) of seed dormancy than does the cumulative growth curve. This appears to be the first report on use of size-class structure to monitor growth of underdeveloped embryos.