The five versions of the M.G. Nikolaeva seed dormancy terminology and formulae system are correlated to each other and to the dormancy terminology proposed by Baskin and Baskin [Seed Science Research14, 1–16 (2004)]. The proposal is made that the dormancy formula scheme of Nikolaeva [Botanicheskii Zhurnal86, 1–14 (2001)] be adopted as part of an international seed dormancy classification system, and her logic for derivation of the new formulae for physiological and morphophysiological dormancy is discussed via examples. We conclude that there are several advantages of adopting formulae into a seed dormancy classification system. However, Nikolaeva's scheme, especially the part for morphophysiological dormancy, probably needs a small amount of further refinement.

The rice (Oryza sativa L.) cv. Taichung 65, a japonica subspecies, was used to characterize the isoform, protein and gene expression patterns of endo-β-mannanase during and after seed germination. Activity assays and isoform analyses of whole grains or seed parts (scutellum, aleurone layer and starchy endosperm) revealed that seeds began to express endo-β-mannanase activity at 48 h from the start of imbibition at 25°C, after the completion of germination of most seeds. Three isoforms of endo-β-mannanase (pI 8.86, pI 8.92 and pI 8.98) were detected in the aleurone layer and starchy endosperm, but only two (pI 8.86 and pI 8.92) were present in the scutellum. The endo-β-mannanase in the starchy endosperm was mainly from the aleurone layer. Western blot analysis, using a tomato anti-endo-β-mannanase antibody, indicated that an endo-β-mannanase protein was present in an inactive form in dry grains. The amount of this protein decreased in the scutellum, but increased in the aleurone layer during and after germination. Thus, the increase in endo-β-mannanase activity in rice grains may be due to the activation of extant proteins and/or the de novo synthesis of the enzyme. Northern blot analysis showed that four putative rice endo-β-mannanase genes (OsMAN1, OsMAN2, OsMAN6 and OsMANP) were expressed in germinating and germinated rice grains. However, OsMANP was not expressed in the scutellum. The amount of OsMAN6 mRNA decreased after the completion of germination and paralleled the decline in endo-β-mannanase protein. In the aleurone layer, the increase of OsMAN2, OsMAN6 and OsMANP mRNA was prior to the increase of endo-β-mannanase protein.

While red rice (Oryza sativa L.) can remain dormant and viable for many years when fully imbibed, the environmental factors that stimulate germination or induce secondary dormancy in the field have not been characterized. In this study, the interactions between the extent of dry-afterripening and germination temperature have been evaluated as possible factors. Red rice dispersal units (florets) were afterripened for 0–10 weeks at 30°C and incubated in water at 1, 5, 15, 20, 25, 30 and 35°C for 2 weeks; then, all the ungerminated florets were transferred to 30°C for two additional weeks. Germination at the end of each of the two sequential treatments was compared to define both the effect of differing temperatures on germination (first treatment), and the effect of these temperatures on subsequent germination at the optimum temperature (30°C, second treatment). In afterripening red rice, the opening of the temperature window for germination begins at 25–35°C. Fully dormant florets acquired the ability to germinate ≥ 90% at 30°C after 4 weeks of dry-afterripening. However, imbibing florets for 2 weeks at 15°C followed by 2 weeks at 30°C, yielded suboptimal germination and induced a degree of secondary dormancy, dependent upon the extent of previous dry-afterripening. Cold stratification (1°C) had a consistent promotive effect on the subsequent germination, particularly when preceded by 1–2 weeks of dry-afterripening at 30°C. To monitor the effects of germination temperature, median afterripening time was utilized as a relative dormancy index, and changes in this index have been interpreted as an overlapping of germination and the temperature-induced changes in the dormancy status. Field weather data suggested that low-temperature stratification may be a germination trigger in the field, even in southern Louisiana, and this merits further investigation in studies of soil-buried seeds.

Torilis japonica (Apiaceae) has a widespread distribution, extending from western Europe to eastern Asia. In Europe, it usually behaves as a spring-germinating biennial species. Ripe seeds of T. japonica have an underdeveloped embryo and can persist in the soil for several years. The aim of this research was to reveal the mechanisms regulating the seasonal emergence pattern of seedlings. Experiments in a natural environment were performed to study phenology of seedling emergence and embryo growth. Seasonal changes in the dormancy status of T. japonica seeds were examined by regularly exhuming buried seeds and incubating them in controlled conditions. The action of temperature and light in regulating dormancy, embryo growth and germination was studied in the laboratory. Results showed that seeds of T. japonica have non-deep, simple morphophysiological dormancy (MPD), whereby physiological dormancy is broken by moist chilling (5°C). Once MPD was broken, embryo growth and subsequent germination started in spring, when appropriate temperature and light conditions were present. Seeds buried at a depth where light could not reach them showed cyclic changes in their dormancy status; embryo growth in these seeds could not be initiated because of the lack of a light stimulus. As far as we know, this is the first extensive study of seasonal dormancy cycles in a spring-germinating species of the Apiaceae. T. japonica occurs in a temperate climate with cool winters and warm, moist summers. In this climate, spring is often the most favourable season for seedling establishment.

Seed salinity tolerance and dormancy play important roles in germination behaviour. The effects of NaCl concentration and different dormancy-breaking treatments on germination were determined for six species growing on the coasts of the Baltic Sea or the Gulf of Riga: Juncus balticus, Triglochin maritima, Triglochin palustre, Anthyllis maritima, Linaria vulgaris and Linaria loeselii. Germination percentages were significantly reduced at NaCl concentrations >100 mM. Germination of J. balticus, T. maritima and T. palustre, but not that of A. maritima and L. vulgaris, recovered after seeds were rinsed with distilled water. Seeds of J. balticus were non-dormant; those of A. maritima had physical dormancy; and those of T. palustre, T. maritima, L. loeselii and L. vulgaris had non-deep to intermediate physiological dormancy, which was broken by cold stratification or gibberellic acid. The seeds of plants growing in habitats periodically exposed to sea water (coastal meadows) were characterized by greater salinity tolerance than seeds of plants growing in habitats less exposed to sea water (dunes).

Previous studies indicated that seeds of Viburnum odoratissimum had only physiological dormancy (PD), but no measurements of embryos were made during the dormancy-break treatments. Thus, we investigated embryo growth and radicle and cotyledon emergence over a range of temperatures. Seeds have underdeveloped embryos, and their length increased about 300% before radicle emergence. Embryos also had PD, as evidenced by delays in beginning of embryo growth (2–3 weeks) and of germination after embryos were elongated (4 weeks). After radicle emergence, epicotyl emergence was delayed 1–8 weeks, depending on incubation temperature, but cold stratification was not required to break PD of the epicotyl. Unlike seeds of many previously studied Viburnum spp., epicotyls of V. odoratissimum have non-deep, rather than deep, PD. Hence, a new level of MPD called non-deep, simple, epicotyl MPD has been identified.