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.

Crop seeds accumulate soluble carbohydrates as part of their maturation process. In legume seeds, the major soluble carbohydrates are sucrose and its galactosides raffinose, stachyose and verbascose. In buckwheat (Fagopyrum esculentum Moench) seeds, the major soluble carbohydrates are sucrose and galactosides of d-chiro-inositol, named fagopyritols. This study was conducted to determine changes in soluble carbohydrate accumulation in embryos of buckwheat seeds after feeding solutions containing the free cyclitols D-chiro-inositol, myo-inositol and d-pinitol to stem–leaf–seed explants. Feeding D-chiro-inositol to explants resulted in a fourfold to fivefold increase in the accumulation of free d-chiro-inositol, fagopyritol A1 and fagopyritol B1 in embryos of mature seeds, but resulted in 30% less embryo dry weight compared to the control treatment without cyclitols. Feeding myo-inositol to buckwheat explants increased d-chiro-inositol in leaves and increased accumulation of fagopyritol A1 and fagopyritol B1 fivefold in embryos, fagopyritol A2 and fagopyritol B2 fourfold; fagopyritol A3 and fagopyritol B3 were also detected, with no reduction in accumulated embryo dry weight. Feeding d-pinitol to buckwheat explants resulted in accumulation of free d-pinitol in mature embryos, but not galactopinitols. D-Pinitol, galactopinitol A and galactopinitol B were not detected in embryos from explants fed solutions without d-pinitol. Feeding d-pinitol also resulted in reduced D-chiro-inositol accumulation by buckwheat seeds. The results indicate that myo-inositol may be the precursor to d-chiro-inositol synthesis, and fagopyritols accumulated in response to d-chiro-inositol availability in the embryo. We suggest that increasing myo-inositol in buckwheat maternal tissues may be an effective means to enhance the accumulation of D-chiro-inositol and fagopyritols in seeds, compounds that may be beneficial for the treatment of non-insulin-dependent diabetes mellitus.

Many research questions focused upon seed dormancy and germination remain unanswered due to problems created by inappropriate assumptions concerning the design and implementation of experiments. Lack of attention to the genetic background and growing conditions required for seed production and subsequent storage may compromise an investigator's ability to pool data or assimilate data trends due to variability in seed performance from year to year. Seed aging events during the afterripening process can be mistaken for those involved in the transition from the dormant to nondormant state. After imbibition, inaccurate criteria for and scoring of the germination event may lead to confusion of seed vs. seedling physiology and biochemistry. In addition, a sufficient number and proper spacing of data points during timecourse experiments are required to properly stage a sequence of events. Studies comparing dormant vs. nondormant seeds must be supplemented with kinetic experiments examining the effect of a dormancy-breaking treatment upon the transition between the dormant and nondormant states. In comparisons of the relative efficacy of various dormancy-breaking chemical treatments, the physical properties of substances under evaluation (e.g. lipophilicity) should be considered. In addition, since many dormancy-breaking chemicals are toxic to vegetative growth, there is a danger of introducing pharmacological artifacts that confuse interpretation of the results obtained. These toxic properties also necessitate the use of viability tests during construction of dose-response curves to avoid confusing seed death with dormancy. Seed scientists must also avail themselves of the extensive literature on developmental arrest in other organisms, which may generate fresh ideas for experimentation.

Depleting the soil weed seedbank is an important integrated weed management strategy that has the potential to foster lasting weed control. Long-term dormancy and decay resistance of weed seeds pose a challenge to weed eradication efforts. Select soil fungi have been shown to cause significant decay of weed seeds. The physical and chemical mechanisms by which seeds in the seedbank defend themselves against pathogens have been well researched. However, very few studies have purposefully investigated the biochemical defence response of seeds. Enzyme-based biochemical seed defences have been detected in dormant and non-dormant seeds, and research supports their function in pathogen defence. This review summarizes current knowledge of the seed defence enzymes polyphenol oxidase, peroxidase, chitinase and oxalate oxidase. The fungal enzymes chitinase, protease and xylanase that function in pathogenesis of seeds in the soil seedbank are also reviewed. Progress in the development and standardization of in situ enzyme analyses fosters our understanding of actual enzyme activity present in soils, while high-throughput microplate techniques promote efficiency and enable greater scope. Application of genomic, proteomic and transcriptomic techniques to glean a deeper and more holistic understanding of the enzymatic interactions of weed seeds and soil fungi in the soil seedbank will support the development of improved integrated weed management strategies.

In contrast to reports in the literature that seeds of Dodonaea viscosa from China and Pakistan are non-dormant, or nearly so, we found that a high percentage of seeds of this species collected in north-western India have a water-impermeable seed coat at maturity, i.e. physical dormancy. Thus, seeds that were mechanically scarified and boiled (to open a ‘water gap’ in the seed coat) germinated to much higher percentages (84% and 77%, respectively) than did those that were non-scarified (24%). Our results agree with studies of seed dormancy in this species in various other parts of its large geographical range.

The factual evidence for aquaporins, the constituents of water channels in cell membranes and operation of water channels is reviewed in developing, maturing and germinating seeds.

Cell cycle activity in dry and germinating untreated and treated (soaked in water and subsequently in fungicide) seeds of two sugarbeet cultivars, collected at commercial harvest time (late mature seeds) and about 2 weeks before this (immature seeds), was investigated by flow cytometry, and by immuno-detection of β-tubulin and the B-subunit of the 11 S globulin. Germination capacity and field emergence were tested. With dry seeds of both cultivars, higher G2 / G1 ratios were observed in the radicle tips of late mature seeds, as compared with those from immature seeds. The late mature seeds contained more partly degraded (soluble) B-subunit of 11 S globulin, typical of germinating or primed sugarbeet seeds. Thus events associated with the onset of germination had occurred in the seed lots collected at commercial harvest time. The cytoskeleton protein β-tubulin was not detectable in dry seeds from either harvest. Western blotting revealed an accumulation of β-tubulin during germination and this was faster in the late mature harvested seeds which was correlated with the onset of DNA replication. Soaking enhanced the rate of cell cycle activation during germination as well as vigour, germination capacity, and field emergence. There was positive correlation between the G2 / G1 ratio and the traits examined in laboratory and field tests. It is concluded that a combined analysis of proteins and cell-cycle-related events can be used in understanding and predicting sugarbeet seed quality.

The seeds of three medics (Medicago orbicularis, M. rigidula and M. rotata) and three clovers (Trifolium stellatum, T. campestre and T. tomentosum) were collected from a pasture in north-west Syria on three occasions: immediately after seed set, at the end of the dry season, i.e. 4 months after seed set, and 16 months after seed set. Complete and sectioned seeds were observed with a scanning electron microscope. Morphological changes and differences in thickness of the seed coat were related to the hard-seededness of the samples collected in the seed bank before the onset of the rainy season. The morphology and structure of the seed coat of all six species were typical of papilionoid legumes. The species with the softest seeds (T. stellatum) showed a very thin and discontinuous cuticular layer at seed maturation (0.16 μm), while a thick and continuous cuticle (4.24 μm) was characteristic of the hardest-seeded species (M. orbicularis). The lens region of seed of all species except T. campestre was weakened after a few months in the field. This weakening was also found in seeds which were certainly hard, but the cracks in the lens region were apparently not deep enough to allow imbibition. Even when large areas of the palisade layer were removed from the lens region of seeds of M. rotata, this was not sufficient to permit water uptake. Differences in the seed coat thickness of the six species accounted for differences in seed dormancy only when seed mass was taken into account.

Seeds of two grass (Arrhenatherum elatius and Festuca rubra), two herb (Plantago lanceolata and Rumex acetosa) and two legume (Lotus corniculatus and Trifolium repens) species were sown in summer 1995 at four densities (no seed, 1000, 10 000 and 50 000 seeds m−2) into an established rabbit-grazed grassland given factorial combinations of rabbit fencing (with and without fences) and soil disturbance (with and without cultivation). On plots where no seeds were sown, only the species with persistent seed banks (P. lanceolata, L. corniculatus and T. repens) showed enhanced seedling emergence in response to disturbance. In disturbed soil, seedling densities of all species increased with increasing density of sown seeds, the effects of which were still evident for plant cover 2 years after seed sowing. In undisturbed vegetation, A. elatius, F. rubra, P. lanceolata and R. acetosa showed increased seedling densities following seed sowing; but in each case, there was an upper asymptote to seedling recruitment, presumably due to microsite limitation. Rabbit grazing reduced seedling densities, with this reduction being more pronounced with disturbance than without. However, the effect of rabbit grazing did not persist for some species; seedling mortality of R. acetosa, P. lanceolata, L. corniculatus and T. repens was higher on plots without rabbit grazing, so that plant densities of these species in summer 1996 and plant cover in summer 1997 were greater on grazed plots. The results indicate interactions between soil disturbance, propagule availability and herbivory, rather than disturbance alone, will play an important role in controlling seedling recruitment and species habitat distributions in grasslands.

Marrow (Cucurbita pepo L.) seed quality was monitored during seed development and maturation in 2 years. Mass maturity (end of the seed-filling phase) was attained 61–63 d and 54 d after anthesis in 1989 and 1990, respectively, when seed moisture contents had declined to 40–48% (wet basis). Considerable dormancy was encountered during standard germination tests, but was overcome by decoating the seeds. The ability of dried, decoated seeds to germinate normally in standard tests reached near maximal values shortly after mass maturity; these values were more or less maintained in seeds from subsequent harvests. Maximum seed longevity in air-dry storage was detected in seeds harvested 24 d (1989) and 26–31 d (1990) after mass maturity. Seedling dry weights 15 d after sowing were greatest for seeds harvested 2–22 d (basal fruits) or 14 d (apical fruits) after mass maturity in 1989, and were positively correlated (P<0.01) with times from seedling emergence to seedling harvest. Consequently in the subsequent year the hypothesis that these differences in seedling dry weight were solely due to differences in times from sowing to emergence was tested (and confirmed). Seedling relative growth rates did not differ with seed harvest date (P>0.25) in 1990, but absolute seedling size did (P<0.005); seeds harvested 21–31 d after mass maturity had the greatest seedling weight and also growth rate (in absolute terms) at any one time after sowing. Decline in seed quality (when assessed by both potential seed longevity and seedling growth) was not detected until the final harvest interval in 1990 (85–90 d after anthesis, 31–36 d after mass maturity). These results for marrow contradict both aspects of the general hypothesis that seed quality is maximal at the end of the seed-filling phase and that viability and vigour begin to decline thereafter.

Seed storage proteins (SSPs) are synthesized during development and the expression of their genes is under tight tissue-specific and temporal transcriptional regulation. In this review we summarize the current knowledge concerning the regulatory steps controlling SSP synthesis in Arabidopsis and cereals, which involves the interaction of cis regulatory elements with corresponding trans-acting factors. In some cases, the regulation of SSP genes requires the concerted action of multiple transcription factors (TFs). There is an evolutionary conservation between the prolamins (the main group of SSPs in many cereal grains) and a major group of dicot seed albumins; this relates to both the regulatory elements and the TFs that are functionally exchangeable between the monocot and dicot species.

A hypothesis by David L. Mulcahy published in Science in 1979 on pollen competition as an important force in the evolution of flowering plant diversity, via selection of favourable genes in the microgametophyte that are passed on to, and inherited in, the sporophyte, stimulated quite a bit of research on the topic. The primary aim of this opinion paper is to assess the evidence for the effect of microgametophyte competition on the sporophyte, with particular reference to seed germination. Pollen competition was associated with an increase in seed germination in 14 of 30 case studies (30 published papers). Seed mass was related to better germination in only two of the 14 cases in which there was a positive effect of pollen competition on germination. An evaluation of the four criteria that must be met to validate Mulcahy's hypothesis cast some doubt on the significance of pollen competition as an important selective force in the diversification of angiosperms. Insect pollination, via which many pollen grains are deposited on a stigma, may not be the answer to Darwin's ‘abominable mystery’ concerning the reason for the abrupt origin and rapid diversification of flowering plants during the Cretaceous.

Abstract An autoradiographic study was made of leucine and thymidine incorporation into the meristematic root primordia and hypocotyl tips of seeds of the recalcitrant mangrove species, Avicennia marina. The investigations show that although there is a temporary reduction of protein synthesis at shedding, root primordia and surrounding hypocotyl cells of the axis never wholly cease incorporation of [3H]leucine and regain pre-shedding levels of activity within a day. Precursor studies using methyl-[3H]thymidine show that, at shedding, there is a temporary cessation of incorporation into root meristem nuclei that lasts no longer than 48 h and, within a day, pre-shedding levels are regained in the meristem nuclei. Analysis of DNA fragmentation patterns in root tips at the time of shedding, and their ability to repair radiation-induced DNA damage, indicate that DNA repair processes are markedly compromised in these cells if water loss reaches 22%. Protein synthesis and DNA replication are reduced by more than half by a water loss of 18% and 16%, respectively. DNA replication does not fully recover on rehydration after only 8% water loss. DNA fragmentation to nucleosomes indicates a programme of cell death at a water loss of 10%. We suggest that the feature of continuous protein synthesis activity with only a temporary interruption in active cell cycling in A. marina root primordia helps to explain both the rapidity in seedling establishment and the extreme vulnerability to desiccation.

Dry plants of Mesembryanthemum nodiflorum L. (Aizoaceae), with mature seeds enclosed in their dry capsules, were collected in the Judean Desert near Jericho, Israel, in the summer of 1972, and have been stored dry under room conditions [15–30°C, 15–25% relative humidity (RH)] since then. More than 31 years after maturation, these unimbibed seeds retained an annual rhythm of germination. A significantly higher percentage of seeds originating from the terminal, central and basal parts of the capsules germinated in February or March compared to other months of the year. This phenomenon was repeated in all three groups of seeds in 2001, 2002 and 2003 for germination in darkness at 15°C, and in terminal seeds germinated at 25°C in darkness for 4 years from 2001 to 2004. The annual rhythm of M. nodiflorum germination may regulate the season and percentage of seeds that germinate at the proper time of the year, even after many years. But the open question still remains: how do dry seeds measure time, and what are the mechanisms involved?

The sorption isotherm for excised embryonic axes of recalcitrant (i.e. desiccation-sensitive) Quercus robur L. acorns was determined to find the relation between moisture content and water potential. Subsequently, physiological studies on the effect of desiccating the axes to a range of water potentials were undertaken. The respiratory capacity declined steeply after short exposure to water potentials from −5 to −30 MPa. The leachate conductivity increased significantly after exposure to −5 MPa and rose steeply after exposure to between −12 and −40 MPa. Axes were equilibrated at different relative humidities and the proline content showed a 15-fold increase with a peak value at −10 MPa. It was concluded that the critical water potential for initiation of damage was −5 MPa, and that axes accumulated proline as a response to desiccation stress. The embryonic axes from Q. robur behave more like typical vegetative tissue of angiosperms than like orthodox seeds.

Coffea arabica L. is highly homozygotic and caffeine content in most cultivars is reported to be similar (approximately 1%). The caffeine content was analysed using individual seeds of cultivars Catuaí Vermelho, Mundo Novo and Bourbon Vermelho, and varieties Mokka and Laurina of C. arabica. Seeds were cut transversely in half, a thin slice from each was extracted in a mixture of chloroform and methanol, and caffeine was measured by high performance liquid chromatography. The extraction procedure was validated by comparison with two conventional methods less suited for analysing large numbers of seeds. The results revealed an unexpectedly large variation [Catuaí Vermelho: 3.72–25.9 mg g− 1 (seeds); Mundo Novo: 5.06–18.59 mg g− 1; Bourbon Vermelho: 6.76–16.59 mg g− 1] even in types naturally low in caffeine such as Laurina (1.17–9.97 mg g− 1) and Mokka (2.01–9.64 mg g− 1). The mean values for all cultivars were always in the range of the caffeine content found in the literature. Several studies showed that C. arabica has approximately 10% cross-pollination, but the variation observed in caffeine content in individual seeds was too large to be explained by cross-pollination.

Total protein content and amounts of albumin, legumin and vicilin have been determined for pea seeds from lines near-isogenic except for genes at the rugosus loci, r and rb (RR/RbRb; rr/RbRb; RR/rbrb; rr/rbrb). Seeds with the wildtype, round-seeded phenotype (RR/RbRb) had less protein on a total seed dry-weight basis than any of the wrinkled-seeded lines and this protein had a lower proportion of albumin. The lines which had recessive alleles at both r and rb loci had the highest proportion of protein and the highest proportion of albumin. The roundseeded peas possessed nearly two-fold more legumin than the double recessive line, with proportions for the two single recessive lines falling in between these extremes. Vicilin levels were similarfor all four near-isogenic lines. SDS-PAGE analysis of the isolated albumin, legumin and vicilin fractions revealed no significant differences between the four lines. Differential scanning calorimetry of protein extracts showed that all the wrinkled-seeded near-isolines possessed legumin fractions with diminished thermal stability relative to that from the roundseeded, wild-type line.

Chemically-induced mutants were also analysed for protein content and composition. These mutants have previously been shown to display great variation in starch and lipid levels. Total protein varied from 20.3% to 37.9%; however, relative proportions of albumin, legumin and vicilin were similar in all mutant lines. SDS-PAGE analysis identified two mutant pea lines which possessed a legumin A-chain of 65 000 Mr as well as the typical 45 000 Mr form. Differential scanning calorimetry of protein extracts indicated that the legumin in all mutants had lower enthalpies of denaturation than the legumin in the round-seeded parent.

The mutant pea lines possess exceptional variation with respect to starch, lipid and protein which raises opportunities for their use in the food and animal feedstuff industries.

Although seed-size preference by granivores is relative to the sizes of seeds offered by researchers, preferences are often inappropriately discussed and interpreted as if they are for absolute seed sizes. Granivores often prefer relatively small seeds in forests and relatively large seeds in herbaceous communities, although the absolute size of preferred seeds in each is often similar. These results are consistent with predictions of optimal foraging theory. Researchers are encouraged to take heed of optimal foraging theory and both relative and absolute seed size when interpreting seed-size preferences.

The genus Conostylis (Haemodoraceae) is endemic to fire-prone south-western Australia. To gain an understanding of the effect of some fire-related germination cues, eight Conostylis taxa were tested in response to water, nitrate, smoke water and karrikinolide (KAR1) under light and dark conditions, when seeds were freshly collected and after a year of burial. The germination of all taxa tested was higher in response to smoke water and KAR1 than in water alone, whereas nitrate did not stimulate germination. Germination was higher in all taxa following 1 year of burial than in fresh seeds. Recently, glyceronitrile has been identified as another chemical in smoke water, apart from KAR1, that can stimulate the germination of certain species. The relative response of eight Conostylis taxa to KAR1, glyceronitrile and smoke water was examined in laboratory-stored seeds. Germination of these taxa was promoted by both smoke water and KAR1, except for C. neocymosa, which had high germination regardless of treatment. Four of the other seven taxa germinated to higher levels in at least one of the glyceronitrile concentrations tested (10, 50 or 100 μM) than in water alone. However, in only two of these taxa, C. aculeata subsp. septentrionora and C. juncea, was germination in glyceronitrile as high as that in smoke water. Thus, the response to glyceronitrile is not uniform across Conostylis taxa. Generally, germination was higher with KAR1 than glyceronitrile, suggesting that although some Conostylis taxa have the capacity to respond to glyceronitrile, KAR1 is the more important germination stimulant for this genus.

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.