Shallow Dormancy Research Articles

Germination specifics and introduction into in vitro culture of Saposhnikovia divaricata (Turcz. ex Ledeb.) Schischk.

The article examines the effect of storage conditions, mericarp processing, and germination conditions of the endemic Saposhnikovia divaricata (Turcz. ex Ledeb.) Schischk. on germination. The technological process of obtaining aseptic in vitro culture was perfected. Mericarps collected from introduced species in 2022 were examined. Explants were sterilized once or twice with 0.1% AgNO3 or 0.1% AgNO3, followed by the use of 10% Н2О2. The pericarp was removed from the sterilized mericarps, and seeds were germinated on a solid 1/2 Murashige and Skoog medium. Callus genesis was induced by culturing the true leaves of seedlings on a Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid (10 μM) and 6-benzylaminopurine (0–5 μM) in the dark. The seeds of S. divaricata exhibit shallow dormancy, and the most favorable conditions for their germination are stratification for 30 days at 4 °С or the scarification of mericarps and germination in an environmental chamber (photoperiod of 16.5 h and a daytime temperature of 27 °С with its slight decrease at night). Laboratory germination capacity reaches 94%. The absence of whole seeds at the end of the experiment suggests a small soil seed bank, which accounts for the vulnerability of natural populations along with monocarpy. The in vitro culture of S. divaricata was obtained. Pericarp removal from mericarps was shown to accelerate germination and improve germination capacity while significantly reducing contamination. A callus was formed on leaf petioles in 66% of explants on an auxin medium, while on a medium with auxin and cytokinin, it was formed across the entire surface of the leaf blade in 72% of explants. Further callus development occurred only on the auxin medium.

БИОЛОГИЯ ПРОРАСТАНИЯ СЕМЯН НЕКОТОРЫХ ВИДОВ ЛУКА (ALLIUM L.)

The possibility of seed reproduction is one of the factors of successful cultivation of resource plants in specific environmental conditions. The aim of the work was to study the germination behavior, quality and longevity of seeds in 15 onions (Allium L.) from the collection of the Central Siberian Botanical Garden SB RAS, Novosibirsk. The research was carried out in 1996–2019. Laboratory germination of seeds was determined according to generally accepted methods. Seeds were tested 3–7 months after harvesting at 17–23 °C in the light. The number of seeds in each Petri dish – 25–50; double replication. In the case of hindered germination, a two-month chilling at 4 °C was applied. In the future, laboratory germination was determined after 3, 5 and 7 years of room storage. We have established that onion seeds have three types of germinating. Seeds of type I – eight species, one variety from the subgenus Rhizirideum – usually lack dormancy. Germination is fast and simultaneous, and average germination percentages are 77.1–92.2 %. Seeds of type II – A. leucocephalum and A. microdictyon from the subgenus Rhizirideum, also A. caeruleum and A. flavum from the subgenus Allium – are characterized by stretched germination period due to the shallow dormancy, and their germination percentages vary from 32.6 % to 81.1 %. Seeds of type III – A. obliquum from the subgenus Rhizirideum and two species of the subgenus Melanocrommyum – do not germinate in room conditions, or germinate with low germination percentages, whereas chilling increases them up to 47.0–67.0 %. The hindered germination of these seeds is due to the deep organic dormancy. The economic longevity of onion seeds is 3–5 years, and the biological longevity varies at interspecific level within 5–8 years. Thus, the species that produce plump and good germinating seeds suitable for long-term storage – A. altaicum, A. bidentatum, A. flavum, A. microdictyon, A. nutans, A. ramosum, A. rubens, A. schoenoprasum, A. senescens, A. senescens var. glaucum, and A. strictum – have the highest reproductive potential in culture.

Seed traits are pleiotropically regulated by the flowering time gene PERPETUAL FLOWERING 1 (PEP1) in the perennial Arabis alpina.

The life cycles of plants are characterized by two major life history transitions—germination and the initiation of flowering—the timing of which are important determinants of fitness. Unlike annuals, which make the transition from the vegetative to reproductive phase only once, perennials iterate reproduction in successive years. The floral repressor PERPETUAL FLOWERING 1 (PEP1), an ortholog of FLOWERING LOCUS C, in the alpine perennial Arabis alpina ensures the continuation of vegetative growth after flowering and thereby restricts the duration of the flowering episode. We performed greenhouse and garden experiments to compare flowering phenology, fecundity and seed traits between A. alpina accessions that have a functional PEP1 allele and flower seasonally and pep1 mutants and accessions that carry lesions in PEP1 and flower perpetually. In the garden, perpetual genotypes flower asynchronously and show higher winter mortality than seasonal ones. PEP1 also pleiotropically regulates seed dormancy and longevity in a way that is functionally divergent from FLC. Seeds from perpetual genotypes have shallow dormancy and reduced longevity regardless of whether they after‐ripened in plants grown in the greenhouse or in the experimental garden. These results suggest that perpetual genotypes have higher mortality during winter but compensate by showing higher seedling establishment. Differences in seed traits between seasonal and perpetual genotypes are also coupled with differences in hormone sensitivity and expression of genes involved in hormonal pathways. Our study highlights the existence of pleiotropic regulation of seed traits by hub developmental regulators such as PEP1, suggesting that seed and flowering traits in perennial plants might be optimized in a coordinated fashion.

Promotive effect of soil solution on germination of Monochoria vaginalis under paddy conditions

ABSTRACTGrowth of the weed Monochoria vaginalis (Burm. f.) Kunth under the conditions of organic rice production is a serious problem. The reason for the growth of M. vaginalis being dominant, especially in organic rice production, is not fully understood. In this study, laboratory experiments were conducted to analyze soil and seed factors in relation to the promotion of germination. (1) After incubation of flooded soil with or without the addition of rice bran (0.3%, 0.6%, and 0.9% in an air-dried soil basis), soil solutions were recovered and seeds of M. vaginalis were incubated in the soil solutions. Germination in the soils solutions without and with 0.3% rice bran was greater than that in distilled water. However, germination was suppressed in the presence of 0.6% and 0.9% of rice bran. These findings indicate that the solution from the soils with rice bran has different effects that may either increase or decrease germination. (2) A mixture of air-dried soil and distilled water was filtered to obtain a soil solution. Seeds were incubated in the soil solution (same as above). Environmental and physiological factors affected germination: exposure of seeds to light was an environmental factor and high germination activity and shallow dormancy of seed were physiological. The recovered soil solution promoted germination when these factors were not optimized. (3) There was a negative and significant correlation between dissolved oxygen (DO) in the soil solution and germination, indicating that a low content of DO was a promotive factor for germination. (4) Based on an experiment using pH buffers, germination increased with decrease in pH of soil solution, as long as the pH ranged from 4.0 to 7.0. This finding indicates that pH is also a factor that promotes germination.

Ecology of seed germination and features of ontogeny of floating mat-forming hygrogelophyte Calla palustris (Araceae) under laboratory conditions

This article examines the ecology of germination and the features of ontogenesis of the floating mat-forming hygrogelophyte Calla palustris L. in the territory of some regions in the central part of European Russia and the Republic of Belarus under laboratory conditions. It has been found that in the surveyed territory in the dense ear-like collective fruit of C. palustris, 40.7 ± 6.4 fruits, juicy berries, are formed and the number of seeds produced (actual seed productivity), averages 164.0 ± 89.3. Widely varying data on the number of berries in the collective fruit, as well as a variable number of ovules in them, shows that the seed productivity of C. palustris depends on a whole range of endogenous and exogenous factors, including the effectiveness of pollination of flowers by insects. In laboratory experiments, various storage periods (2 and 12 months) and methods of presowing seed treatment (stratification, drying, ice-freezing) were applied to simulate the ecological conditions of the growth of white alder. It is shown that freshly harvested seeds do not germinate at once, and wet cold stratification makes it possible to achieve maximum values of laboratory germination (from 84.4 to 99.0) and germination energy (from 66.6 to 88.3). Given that the features of germination are indicators of dormancy, it is demonstrated that seeds of C. palustris are in a state of shallow physiological dormancy, conditioned by the physiological mechanism of inhibition. Along with dry storage, wet cold stratification is the main way for seeds to enter a non-dormant state. Such mechanisms are consistent with the climatic features of the regions in which the species grows. It is found that C. palustris seeds, in common with many other species of hygrogelophytes, can float on the water surface for a long time (more than 30 days), spreading with water flow (hydrochoria). Seeds of C. palustris are photosensitive, germination is observed in a wide range of temperatures – from 10–14 to 30 ºС (at constant humidity), type of germination – underground (hypogeal). It is found that ontogeny of individuals of generative origin of C. palustris in the laboratory is terminated (the plants died after passing the juvenile ontogenetic state). The formation of C. palustris seedlings under laboratory conditions lasts 23–25 days and is characterized by the appearance of the main organs of the plant and the anisotropic growth of the shoot axis. At the final stage of development, the seedling is represented by a uniaxial monopodial and anisotropic growing rosette shoot with shortened internodes. The juvenile ontogenetic state in laboratory conditions lasts up to 7 months, after which the plants die off. In the framework of ontomorphogenesis, the stages of ontogenetic development under study (the seedling and the juvenile plant) correspond to the phase of the primary uniaxial rosette shoot. The plant in this period is represented by a uniaxial monopodially growing anchorage shoot. The detection of virgin plants in natural conditions indicates the possibility of their further development from the rudiments of generative origin. The main way of the species reproduction is vegetative, characteristic of most aquatic and semi-aquatic plants. In the course of ontogenesis, progressive features of development such as cotyledon greening and early death of the radicle root have been revealed.

Cucumber CsBPCs Regulate the Expression of CsABI3 during Seed Germination.

Cucumber seeds with shallow dormancy start to germinate in fruit that are harvested late. ABSCISIC ACID INSENSITIVE3 (ABI3), a transcription factor in the abscisic acid (ABA) signaling pathway, is one of the most important regulators in the transition from late embryogenesis to germination. Our analysis found a candidate cis-regulatory motif for cucumber BASIC PENTACYSTEINE (CsBPC) in the promoter of CsABI3. Yeast one-hybrid and chromatin immunoprecipitation (ChIP) assays showed that CsBPCs bound to the promoter of CsABI3. Examination of β-glucuronidase (GUS) activity driven by the CsABI3 promoter in transgenic Arabidopsis thaliana plants overexpressing CsBPCs and a Nicotiana benthamiana (tobacco) luciferase assay indicated that CsBPCs inhibited the expression of CsABI3. Transgenic plants overexpressing CsBPCs were constructed to confirm that CsBPCs participates in the control of seed germination. This study of the cucumber BPC-ABI3 pathway will help to explore and characterize the molecular mechanisms underlying seed germination and will provide necessary information for seed conservation in agriculture and forestry.

Can “Caricia” and “Princesa” apples be considered low-chilling cultivars?

The purpose of this work was to study the response of two apple cultivars bred for low chilling environments to artificial chilling accumulation. Two trials were carried out; in experiment one, excised shoots were randomly taken from “Caricia” and “Princesa”, and in experiment two, intact and excised shoots of “Caricia”, “Princesa” and “Gala” (control) were collected. After collection, both shoot types were exposed to artificial chilling accumulation (4.0 ± 0.5°C) from 0 to 1200 chill units (CU). Bud break of mixed buds of “Caricia” and “Princesa” was higher than 50% between 0 CU to 1200 CU, irrespective of shoot type. Bud break of “Gala” mixed buds exceeded 50% only in intact shoots after accumulating 900 CU. The mean time to bud break of “Caricia” and “Princesa” diminished with increasing chilling accumulation and stabilized after ~600 CU, depending on the type of shoot and the year of experimentation. The low-chill apple cultivars tested in this work showed shallow dormancy, but they required moderate cold accumulation (800 – 1150 CU) to fully satisfy their chilling requirements. Thus, although their shallow dormancy makes them suitable for cultivation in chill-deficient environments, they cannot be considered low-chill cultivars.

Features of seed germination in different ecological groups of the species of the section Violidum, subgenus Nomimium, genus Viola L. (Violaceae)

This article presents the results of seed germination in different ecological groups in the species (22 populations) of the section Violidum, subgenus Nomimium, genus Viola. Conditions for seed germination, as well as germinating ability, germination energy, intensity of germination energy, longevity of seeds and profitability of their ability, and the period when the seed germinating ability decreases by 50% (P50) have been determined. The seeds of most species of xeromesophytes and mesophytes massively germinate at +23…+25°C within a period of 10 days. For other species of these ecological groups, cold stratification is favorable. The hygromesophytes are characterized by prolonged seed germination (up to 2 months). The petrophyte seeds have shallow physiological dormancy (B1). The seeds of other species are, as a rule, nondormant.

Environment sensing in spring‐dispersed seeds of a winter annual Arabidopsis influences the regulation of dormancy to align germination potential with seasonal changes

Seed dormancy cycling plays a crucial role in the lifecycle timing of many plants. Little is known of how the seeds respond to the soil seed bank environment following dispersal in spring into the short-term seed bank before seedling emergence in autumn.Seeds of the winter annual Arabidopsis ecotype Cvi were buried in field soils in spring and recovered monthly until autumn and their molecular eco-physiological responses were recorded.DOG1 expression is initially low and then increases as dormancy increases. MFT expression is negatively correlated with germination potential. Abscisic acid (ABA) and gibberellin (GA) signalling responds rapidly following burial and adjusts to the seasonal change in soil temperature. Collectively these changes align germination potential with the optimum climate space for seedling emergence.Seeds naturally dispersed to the soil in spring enter a shallow dormancy cycle dominated by spatial sensing that adjusts germination potential to the maximum when soil environment is most favourable for germination and seedling emergence upon soil disturbance. This behaviour differs subtly from that of seeds overwintered in the soil seed bank to spread the period of potential germination in the seed population (existing seed bank and newly dispersed). As soil temperature declines in autumn, deep dormancy is re-imposed as seeds become part of the persistent seed bank.

Inheritance mode of seed dormancy in the hybrid progeny of sesame, Sesamum indicum, and its wild relative, Sesamum mulayanum Nair

Sesamum mulayanum is a wild relative of cultivated sesame, Sesamum indicum, and sometimes grows in sesame crop fields as an associated weed. This species shows deep seed dormancy and is characterized by conspicuous purple pigmentation on the lower lip of the corolla. The present study examined the inheritance mode of seed dormancy by using reciprocal progeny from crosses between the two species. The seeds of S. indicum and F1 (S. indicum×S. mulayanum) showed good germination, but those of S. mulayanum and F1 (S. mulayanum×S. indicum) showed deep dormancy. The F2 seeds from both reciprocal crosses showed deep dormancy. These results, combined with the maternal inheritance of seed-coat characteristics, indicated that the seed dormancy of S. mulayanum can be attributed to its seed-coat structure (coat-enhanced dormancy). The F3 (S. indicum×S. mulayanum) seeds varied in their depth of seed dormancy and those seeds with deep dormancy (<50% germination) and those with no or shallow dormancy (≥50% germination) occurred in the expected ratio of 3:1, indicating that this trait is polygenic but is controlled by a single dominant major gene. The purple pigmentation of the corolla was expressed in both reciprocal F1 plants and the presence and absence of pigmentation was segregated among the F2 plants at the expected ratio of 3:1, indicating that this trait is also controlled by a single dominant gene. The segregation of the major gene controlling seed dormancy and that controlling purple pigmentation was not independent (9:3:3:1), indicating that these genes are linked, providing insights on sesame domestication.

Morphological and biochemical changes of Aesculus chinensis seeds in the process of maturation

Morphological and biochemical changes of Chinese horse chestnut (Aesculus chinensis Bge.) seeds were studied during the process of maturation. Fruit and seed diameter increased linearly from DPA (Days Post Anthesis) 60 to DPA 150 and were stable thereafter. The weight of fruit and seed increased sigmoidally between DPA 100 and DPA 160. The water contents of whole seeds, axes and cotyledons had a sharp reduction from DPA 110 to DPA 130 but changed little after DPA 130. The water contents of whole seeds, axes and cotyledons were 1.42, 1.93 and 1.30 g g−1DW, respectively at the end of maturation. The starch content of cotyledons from mature seeds was high on a dry weight basis (31.4%) while the total soluble sugar content varied between 12 and 20%. In both axes and cotyledons, the total soluble sugar content decreased during the process of maturation, as did all five soluble sugar components measured (glucose, sucrose, trehalose, raffinose and stachyose). Sucrose and stachyose contents remained relatively high at the time of seed maturation, followed by glucose and a trace level of trehalose. The oligosaccharide/disaccharide (O/D) ratio in the axes was 3.1 at DPA 140. The high level of sucrose and stachyose might contribute to the greater desiccation tolerance of Aesculus chinensis seeds relative to typical recalcitrant tropical seeds. High levels of ABA content in seed coats and a low GA3/ABA ratio in both seed coats and axes might also influence the desiccation tolerance and shallow dormancy of mature Aesculus chinensis seeds.

JUDGMENT INDEX AND INHERITANCE OF CHILLING REQUIREMENT TO BREAK DORMANCY IN STRAWBERRY

Strawberry cropping systems adapted to each district from the southern to northern parts of Japan were developed together with advancing of studies on ecotype characteristics of various cultivars and techniques of controlling flower induction and dormancy, resulting in many cropping systems. The cultivars adapted to forcing culture have shallow dormancy and those adapted to semi-forcing culture and open culture have deep dormancy. This experiment was carried out to determine a judgment index for the chilling requirement to break dormancy and to investigate the inheritance of dormancy in strawberry plants. Runner plants of 8 varieties with various chilling requirements to break dormancy were exposed to varying degrees of chilling under 5°C. Runnering was a more effective index than the sudden extension of petiole length. Moreover, the cessation of continuous flowering under the minimum temperature of 15°C with a 16h photoperiod was used to judge the chilling requirements to break dormancy because the coefficient of variation of runnering was smaller than that of the sudden extension of petiole length and the cessation of continuous flowering. Chilling requirements and the cumulative hours of chilling to break dormancy of the runner plants were longest, while that of the over-wintered seedlings was longer than that of the annual seedlings. Runner plants of the selfed seedlings and the crosses between seedlings of a shallow dormancy variety 'Nyoho' and deep dormancy varieties 'Aiko' and 'Pajaro' were used to investigated the inheritance of dormancy. The degrees of dormancy of the crossed seedlings were tend aside of parents with shallow dormancy. It seems that the selection of strawberry plants with deep dormancy needed the use of many seedlings.

Phenolic acids in caryopses of two cultivars of wheat, rye and triticale that display different resistance to pre-harvest sprouting

This study confirmed the significant role of phenolics in the dormancy of cereal caryopses. Investigations were conducted on two cultivars of wheat (Elena and Alba), rye (Amilo and Dankowskie Zlote), and triticale (Ugo and Bogo), with characteristic deeper or shallow dormancy, respectively. In germination studies, cultivars susceptible to sprouting (Alba, Dankowskie Zlote and Bogo) displayed higher germination percentages than those resistant to sprouting (Elena, Amilo and Ugo). The phenolic acid contents (i.e. free, liberated from soluble esters, and liberated from soluble glycosides) in caryopses were determined by an HPLC method. Caffeic, p-coumaric, ferulic and sinapic acids were the dominant phenolic acids detected. The majority of phenolic acids were found in the form of soluble esters. For all species examined, the levels of phenolic acids liberated from soluble esters and the total phenolic acid contents in caryopses showing shallow dormancy were higher than in those showing deeper dormancy. Slight differences in the UV spectra of extracts of phenolic compounds from caryopses showing shallow or deeper dormancy were noted.

Age, Growing Temperatures, and Growth Retardants Influence Induction and Length of Dormancy in Malus

Apple seedlings have a shallow dormancy, as has been observed in many other species. The length of bud dormancy in high-chilling-requirement seedlings does not reflect their genetic constitution well if dormancy is induced before they are 200 days old. Seedling populations sprayed with paclobutrazol and/or ethephon displayed bud dormancy periods resembling those of older populations of similar genetic constitution. Terminal bud formation and dormancy could not be induced by continuously exposing apple seedlings to low temperature (8 ± 1C) and short photoperiod, even after extended periods. Stomate operation may not be completely functional under these conditions. Terminal bud formation was induced by holding apple seedlings above 20C. Additional exposure to low temperature (8 ± 1C) induced leaf fall. These findings suggest the existence of an active regulatory factor that induces terminal bud formation and dormancy and is either turned on or synthesized above 15 to 17C. Chemical names used: β- [(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol(paclobutrazol);(2-chloroethyl)phosphoric acid (ethephon).

Collection and care of sweetgum seed

Sweetgum (Liquidambar styraciflua L.), a widely distributed hardwood in the United States and Central America, shows potential for tropical forestry application. Fruit heads change from bright green to yellow in color as they mature, and they can be picked from standing trees or logging slash when the color change occurs. Fruits release their seeds after only moderate drying, and cleaning is easy with air-screen cleaners. Sweetgum seeds are orthodox in storage behavior, and they should be stored at moisture contents of 5 to 10% at 0° to 5° (5 years or less) or −18° (more than 5 years). The seeds exhibit a shallow dormancy that can be overcome with 2 to 4 weeks of stratification at 3°C.

Studies on the Breaking of Dormancy in Barnyardgrass Seed : II. Change of the dormancy-breaking effect of several inhibitors against oxidation-reduction system by dormancy stage

This paper forms the second part of a series of investigations on the control of the breaking of dormancy in barnyardgrass (Echinochloa Crusgalli Beauv. var. oryzicola Ohwi) seed. This investigation evaluated the change of the dormancy-breaking effect of several inhibitors against oxidation-reduction system through the process of the breaking of dormancy. 1) In deep dormancy stage, 8-oxyquinoline, KCN, DIECA, HgCl2, Na2S and salicylaldoxime-all showed a stimulative effect on the breaking of dormancy in considerable degree. But thiourea, NaN3 and BAL had no effect. 2) In deep dormancy stage, the inhibition of oxygen uptake by salicyladoxime, DIECA or HgCl2 was no more than 30 percent under the treatment inducing the dormancy-breaking effect. In addition, thiourea did not inhibit the oxygen uptake under the same treatment. 3) In shallow dormancy stage, the dormancy-breaking effect of KCN and HgCl2 increased remarkably. However, 8-oxyquinoline, DIECA and salicylaldoxime showed less effect than KCN and HgCl2. 4) The effect of 8-oxyquinoline in shallow stage was inferior to the level in deep stage by all means of treated period or concentration. 5) On the contrary, NaN3 had a noted effect only in shallow stage. These results indicate that the endogenous mechanism of dormancy in barnyardgrass is changing gradually, corresponding with the environmental conditions.

Dormancy of peanut seeds

1. Small seeded varieties of Spanish and Valencia types showed only shallow dormancy just after harvest, but large seeded varieties of Virginia type showed deep dormancy continuing during rather long period.2. Differences of nature of dormancy due to difference of growing areas between Japan and Israel could hardly been observed.3. Preheating for two to three days at 60°C or seven to 14 days at 45°C was most effective for breaking dormancy of peanut seeds. This treatment is usable for routine works.4. Entire or partial decoating is much effective for breaking dormancy. Presoaking also induces rather high germination. Accordingly, the cause of dormancy of peanut seeds seems to be due to germination inhibitors contained in the seeds. These inhibitors are thought to be contained in both seed coat and embryo during some period after harvest, but to become soon contained only in seed coat.

The morphological and ecological studies on the cultivated and wild Mitsuba Cryptotaenia japonica HASSK

Cryptotaenia japonica HASSK., hence forward referred to by its generic name alone, is a member of Umbelliferae. It is a herbaceous perennial plant indigenous to the Far East Asian temperate zone and is commonly cultivated throughout Japan as a vegetable crop. It grows widely in the mountainous regions of the country in wild state and is called as“Mitsuba”in Japanese.Thirty-six wild-grown stocks and five cultivars of Cryptotaenia, collected from various parts of Japan, were cultivated in Sakai, Osaka prefecture. The morphological and ecological studies were made during 1955-1958 on varietal differences among the cultivars and characteristic differences between the wild strains and the cultivars of Cryptotaenia, . The geographical differentiations among the wild strains were also investigated.1. In comparison with the wild strains, all of the cultivars had generally more valuable morphological characters as a vegetable crop and uniformity among the cultivars. Green color of the leaf and stem, erect plant type and large size of the plant are very distinctive features. On the contrary, the wild strains showed a wide range of variations in characters and the plants generally tended to be more prostrate in plant type, but there was no apparent relation between the characters and geographical conditions of the native habitat.2. In regard to the bolting and flowering time, all of the cultivars and the wild strains collected from warm climate zones showed the tendency of earlier bolting and flowering than those from cooler climate zones. It was found that the time of bolting and flowering of the wild strains is related to the latitude and temperature of the areas where they were collected.3. Varietal differences of premature bolting of the cultivars distributed in both Kanto and Kansai districts were investigated by means of four different sowing trials at different time. It was found that the cultivars of Cryptotaenia can be divided into two main ecological types, namely the Kansai Ao-mitsuba of early-bolting and the Kanto Shirokuki-mitsuba of the late-bolting. Both types seem to have been selected for the special methods of cultivation in these two districts.4. A similar geographical trend as seen in the bolting and flowering time was found in the seed dormancy of wild Cryptotaenia collected from cool climate zones when they were sowed immediately after harvest, while strains having none or shallow dormancy were found in both of the cultivars and the wild strains collected from warm climate zones.Effective treatments for breaking the seed dormancy are also investigated, and a chilling pretreatmemt at 5°C for 10-60 days was effective, but the optimum period of chilling varies with strains.