The technique of radioimmunoassay following sample resolution by HPLC was used to assay the amounts of the cytokinins zeatin (Z), zeatin riboside (ZR) and isopentenyladenine (IPA), the combined amounts of gibberellins1+3 (GA1+3), and the amounts of indole acetic acid (IAA) and abscisic acid (ABA) during germination in grains of sorghum. Concentrations of GA1+3 were low throughout germination and did not appear to be related to the time of germination. In the mature, non-germinated grain, the concentration of each of the other plant growth regulators was much higher in the smaller component comprised of the embryonic axis and scutellum than in the much larger endosperm tissue. During the germination period studied (64 h), these concentrations declined, with a peak in the amount of the cytokinin IPA and a small peak in Z+ZR (24 h) in the embryo following the first visible signs of root protrusion and coincident with a large enhancement in amylase activity. The high concentration of ABA in the embryo tissue prior to germination was noteworthy. It is suggested that the interaction of ABA and the cytokinins IPA and Z+ZR may play a significant role in controlling sorghum germination.

In the range of water contents studied (0.1–0.4 g H2O g dw−1), Coffea arabica seeds were less sensitive to desiccation than C. costatifructa, C. racemosa and C. sessiliflora seeds. At 0.20 g H2O g dw−1, 53% of C. arabica seeds germinated after direct immersion in LN (rapid cooling, 200°C min−1), but none of them developed into normal seedlings. By contrast, in C. costatifructa, C. racemosa and C. sessiliflora, when seeds were dehydrated to the optimal water content (0.19, 0.28 and 0.31 g H2O g dw−1, respectively), the percentages of seeds which developed into normal seedlings after LN exposure were 26, 78 and 31% of the desiccation control, respectively. Normal seedlings could be recovered from cryopreserved C. arabica seeds only if they were desiccated to 0.20 g H2O g dw−1 and precooled slowly to −50°C prior to immersion in LN. Precooling seeds at 2°C min−1 allowed 25% of seeds to develop into normal seedlings. The thawing rate had no effect on the survival of cryopreserved C. arabica seeds. In all cryopreservation experiments, the total germination did not reflect the percentage of seeds which developed into normal seedlings. Examination of excised embryos indicated a partial explanation of this difference since only the shoot apex was destroyed in abnormal embryos, whereas the hypocotyl and radicle were normal.

Submerging Phaseolus vulgaris cv. Top Crop seed in air-saturated water for 16 h markedly depresses subsequent germination. This is termed soaking injury. The postulate by Norton (1986) that soak-injured seeds merely run out of available energy was investigated. Soaking in air-saturated water reduced the total respiration (VT; in terms of O2 uptake) of excised axes and cotyledons resulting in lower ATP levels. The contribution of both the mitochondrial cytochrome respiratory pathway (VCYT) and the alternative respiratory pathway (VALT) to the total respiration (VT) was significantly lower in these axes. However, the adenylate energy charge (AEC) values for both axes and cotyledons excised from soak-injured seeds did not drop below 0.6, the threshold value indicating death of plant material. Differences between the ultrastructure of mitochondria in the radicle tips of axes from unsoaked and water-soaked seeds were observed. However, the capacity to operate the Krebs cycle was similar in all axes and soak-injured seeds were still capable of germinating when the testas were removed or the seeds dried. This means that axes contained a sufficient amount of carbohydrates and potential energy to germinate after soaking. Moreover, soak-injured seeds produced ethanol at a rate which was five times higher than that of unsoaked control seeds, both during the soaking and post-soaking periods. Together with the low rate of oxygen consumption by soak-injured seeds during the same soaking and incubation time, it appears that soak-injured seeds lack the potential to switch from an anaerobic to an aerobic respiration pattern causing low ATP levels in these axes. It is speculated that the latter seems to be the result of limited pyruvate supply, probably due to accelerated and prolonged fermentation or futile combustion through other pathways or both.

Variation in dormancy level was tested in seeds of four species, each collected from three populations in 1994 and 1995 (experiment 1). Germination was tested in light and darkness on recently-harvested seeds and on those after-ripened in dry storage for one year. In addition, seeds from each of eight individual plants within each of eight populations were tested for germination when recently harvested and after warm stratification or cold stratification followed by a drying period (experiment 2). Seeds from the two years differed in dormancy level in Silene noctiflora, Sinapis arvensis and Spergula arvensis. Germination percentage differed significantly among populations in Sinapis arvensis and Spergula arvensis in both experiments and in Thlaspi arvense in experiment 2. Furthermore, dormancy level in seeds from different mother plants also varied in the three species tested in experiment 2. Variations at the three levels tested (year, population and mother plant) indicate that these species have a random pattern of variation in dormancy level. It is concluded that variation in seed dormancy among mother plants, populations and years must be taken into account when testing the germination characteristics of a species and also when attempting to model weed seed bank dynamics.

The spatial variation of the soil seed bank in the steppe of Larrea divaricata and Stipa spp. was evaluated in relation to the spatial pattern of the established vegetation, over two years. Plant distribution was expected to affect the spatial pattern of the soil seed bank. It was hypothesized that patches of bare soil are seed-limited, while soil beneath the external crown of vegetation patches contains greater numbers of seeds. The soil seed bank of the steppe of Larrea divaricata and Stipa spp. displayed a patchy distribution associated with the spatial pattern of above-ground vegetation. Seed banks in areas of bare soil showed lower numbers of seeds than those beneath vegetation. The soil seed bank was dominated by annuals, both in open areas of soil and under vegetation canopies. The relative composition of the soil seed bank varied spatially. Annuals (dicots and grasses) were more abundant in grass-shrub patches (GSP) and grass patches (GP) than in incipient grass-shrub patches (IGSP) and bare soil (BS). Seeds of perennial grasses were more abundant under GP, less abundant under grass-shrub mixed canopies (IGSP and GSP) and practically absent in BS. In addition, seeds of perennial dicots were more frequent in grass-shrub mixed canopies, scarcely represented in GP and absent in BS. The concentration of seeds of perennial grasses in GP and GSP indicates that these are essential for the maintenance of the size of grass populations. Sustainable management should be focused to maintain the structure and function of these types of vegetation patches.

This is the first report on the SEed Ecological Database (SEED) being developed under the co-ordination of the author. In its first version the database will cover physical characteristics of seeds, such as: slenderness (length/width), flatness (thickness/width) and thousand-seed weight. The list of species encompasses all seed plants (gymnosperms and angiosperms) native or naturalized in Hungary (about 2450 species). Two examples to demonstrate the power of SEED are included. The significantly lower slenderness values of Hungarian C4 grasses (compared with C3 types), shown in the first example, is a new contribution to understanding the ecology of C4 grasses. In the second example heavier seed weights of shade plants are statistically demonstrated, compared to their heliophilous congeners with the same life forms. The 113 congeneric species pairs considered are derived from a wide range of plant families.

Seed-bank dynamics of C. controversa, a common tree in Japanese temperate forests, were investigated at Ogawa Forest Reserve by direct measurement of seed input, soil seed density, and seedling output (germination of soil seeds), together with two field experiments on postdispersal seed mortality. Soil seed density varied from 4 to 233 m−2 in the site near conspecific adults (<5 m horizontally from crown edge), and 0 to 18 m−2 in far sites (≥5 m) during the 1988–92 period. Seed input occurred only in 1988 and 1990: 190–740 m−2 at the sites near conspecific adults, and 4–20 m−2 at the far sites. Seedling output was observed every year and accounted for 0–15% of the loss from the seed bank, occasionally 30–60%. Seeds buried at 5-cm depth suffered moderate mortality (c. 0.2 year−1) by fungal pathogens. In contrast, seeds experimentally placed on the ground suffered higher mortality (0.5–1 year−1) through predation by ground mammals, probably wood mice. In the experiment, seeds whose mesocarp was removed survived much better. On the other hand, distance itself did not appear to affect post-dispersal mortality of seeds. Seeds in canopy gaps also tended to suffer higher mortality. Current spatial pattern and mode of seed dispersal should decrease the potential ability of the seed bank of this species to colonize safe sites. Rare and unpredictable events might increase the contribution of the seed-bank strategy to regeneration in this forest.

Seeds of the geographically-widespread Solidago altissima and S. nemoralis and the narrow-endemic S. shortii were buried in pots of soil and placed in a glasshouse without temperature control. After 0.3–4.3 years of burial, some seeds (21–60%) of all three species were viable and they germinated to 75–100% during 2 weeks of incubation in light at 30/15°C. Soil samples collected from several population sites of S. altissima, S. nemoralis and S. shortii were placed in the glasshouse and monitored for seedling emergence. During the first, second, third, fourth, fifth and sixth springs, the number of S. altissima seedlings m−2 emerging was 108–1080, 8–494, 0–520, 0–69, 0–6 and 3, respectively, of S. nemoralis was 108–1122, 17–667, 0–42, 0–6, 0, 0 and 0, respectively, and of S. shortii was 61–1753, 0–25, 0–6, 0, 0 and 0, respectively. More seedlings emerged from disturbed than from non-disturbed soil, but the differences were not significant. Thus, although some seeds of all three species buried in pots remained viable in soil throughout the 4.3-year burial period, longevity was greater and size of seed bank larger in field-collected soil samples containing seeds of the geographically-widespread species than in those containing seeds of the narrow endemic. Although 34 studies have reported seeds of 17 species of Solidago present in soil seed banks, the present study is the first to show, conclusively that Solidago can form a persistent seed bank.