Depth Of Dormancy Research Articles

The effects of light quality, nitrate concentration and presence of bracteoles on germination of different fruit types in the heterocarpous Atriplex sagittata

Summary We investigated the effect of light quality, nitrogen supply, fruit size and age on germination of the three types of fruit produced by Atriplex sagittata. Regardless of fruit type, seed germination was significantly reduced in the dark. Light quality had no significant effect on germination of seeds from fruit types A and B, both of which are dormant, but seeds from fruit type C, which are non‐dormant, germinated better in green light (low photon flux and red : far‐red ratio, simulating conditions in the canopy) than in white light. Optimum nitrate concentration differed between seed types but, for all, germination was reduced at the highest concentration used. The effects of cold stratification and its interaction with light and nitrogen effects were also studied. Strong interactions between stratification and light were found in all seed types but other interactions were less frequent. Three size classes of type C fruit showed similar final germination percentages but large seeds germinated more slowly. The effect of seed age was highly significant: over a 3 year period, the germinability of dormant seeds (types A + B) increased while that of non‐dormant seeds (type C) fell. The salt concentration in bracteoles of freshly ripened fruits was too low to mediate an inhibitory effect on germination. Moreover, the first autumn rain would be sufficient to remove all the salt from bracteoles. Differences between fruit types in depth of dormancy, and in response to the quality of light and to nitrate concentration in the soil, allows A. sagittata to respond to the spatial and temporal variation in environmental conditions encountered by this annual of disturbed habitats.

Depth of dormancy in tomato (Lycopersicon esculentum Mill.) seeds is related to the progression of the cell cycle prior to the induction of dormancy

Cell cycle activities are initiated following imbibition of non-dormant seeds. However, it is not known whether cell cycle related events other than DNA replication also remain suppressed in imbibed dormant seeds. The objective of this study was to demonstrate that the transitions between the non-dormant and dormant (both primary and secondary) states are reflected in cell cycle events, such as DNA replication and the changing patterns of the microtubular cytoskeleton involved in the processes of growth and development. The present studies were conducted on seeds from tomato (Lycopersicon esculentum cv. Moneymaker) that possessed primary dormancy or were manipulated to attain secondary dormancy. In addition, a non-dormant abscisic acid (ABA)-deficient mutant, sitw, was used. DNA replication, as measured by flow cytometry, and β-tubulin accumulation, analysed by immunoblotting, were compared with immunocytological studies of active DNA synthesis and microtubular cytoskeleton formation. It is shown that the depth of dormancy, which distinguishes primary and secondary dormancy, may depend on the progression of the cell cycle prior to the induction of dormancy.

Effect of Industrial Environmental Pollution on Winter Dormancy in Scotch Pine

Many complexes of adaptive responses to environmental factors that have been formed in the course of evolution change under the effect of technogenic pollution. Disturbance of the natural dynamics of transition to winter dormancy in woody plants is among the possible manifestations of this effect. We may presume that, as a result, some of the plants growing in regions with a high level of air pollution do not complete their transition to dormancy, remain unprepared for severe conditions in winter, and may be damaged. Apparently, this is actually the case, as the composition of sugars in plant leaves changes under the effect of air pollution, and the increase in their contents in autumn and winter is less pronounced and occurs later than under normal conditions (Huttunen et al. , 1981b). Seasonal dynamics of transpiration rate is also altered in plants growing in polluted areas (Huttunen et al. , 1981a). To resolve this issue, it is necessary to study in detail the seasonal dynamics of the state of plants, including their transition to winter dormancy, using adequate methods for monitoring their physiological condition. Measurement of chlorophyll fluorescence is one such approach. It allows the researcher to estimate structural and functional changes in the photoassimilatory system of plants (Matorin et al. , 1985; Veselovskii and Veselova, 1990; Gaevskii and Morgun, 1993; Grigor’ev and Buchel’nikov, 1999). The purpose of this study was to analyze the seasonal dynamics of chlorophyll fluorescence in the needles and the depth of winter dormancy in Scotch pine trees ( Pinus sylvestris L.) growing in areas with different levels of air pollution.

Changes in endogenous ABA level in relation to the dormancy cycle in grapevines grown in a hot climate

SummaryIn warm-winter regions, the need for artificial means to compensate for the lack of natural chilling becomes a dominant factor for maintaining economic production of table grapes. However, in the absence of a reliable method of predicting the time of natural bud break, the application of the dormancy breaking agent hydrogen cyanamide (HC) entails the risk of serious bud damage if the application is mistimed. In several studies in temperate regions, concentrations of endogenous abscisic acid (ABA) were found to increase as the grape buds entered dormancy, and to decrease during winter months towards dormancy release. To assess the possibility of using bud ABA content as a marker for the stage of bud dormancy in grapevines grown in hot regions, we evaluated the dormancy depth of grape buds in the course of the dormancy cycle and monitored their endogenous ABA content in cv. Perlette vines grown in the Jordan Valley. The endogenous ABA content was highest at maximum dormancy. However, the decline in ABA content was not correlated with dormancy release. The involvement of ABA in dormancy induction and maintenance is discussed.

Yield parameters in young jojoba plants and their relation to actual yield in later years

A total of 30 jojoba clones, among them six already commercial clones and 24 newly selected ones were characterized in terms of yield parameters, chilling requirements and morphological traits. The aim was to supply farmers (from Israel and abroad) better yielding clones. Considerable variability was found among the clones in all the parameters. Some clones exhibited excellent vegetative traits related to yield potential, such as a high survival rate, rapid growth, extensive branching, high node density, while others exhibited outstanding reproductive traits, such as earliness, high flower density, high percentage of fruit set, high seed weight, and high wax content in the seed. The clones also differed in their wax composition. Plants began to yield 2 years after planting in the field, some having commercial yields as early as their third year. The best clones with respect to wax yield were Hazerim, Negev, BGU, Forti, and Gvati, all new clones not yet planted in commercial plantations. An attempt to relate yield parameters at the third year to wax yield at their sixth year was made. The height in the third year and the flower index, relative fruit set and seed weight were related to yield. The flowering pattern of all clones was followed up during the season 1993/94, which was characterized by a combination of cool night temperatures with warm days. This weather enabled the clones that broke dormancy to flower during the winter instead of spring. We were thus able to identify clones with different chilling requirement. In conclusion some very promising clones with high yields can be added to our commercial clones. Owing to the new information gathered on depth of dormancy and flowering pattern, clones can also be allocated to environments differing in climatic conditions.

Evidence for the role of abscisic acid in the genetic and environmental control of dormancy in wheat (Triticum aestivumL.)

AbstractGrain production of two wheat cultivars (Triticum aestivum L. cv Recital and Scipion), known for their different germination behaviour, was studied at two different temperatures. The study of dormancy onset during grain development showed that in both cultivars, dormancy developed on the mother plant. In Recital grain, after a period of high germinability, dormancy developed for a transient period. However, full germination was obtained on medium supplemented with fluridone, showing that dormancy was associated with abscisic acid (ABA) biosynthesis inside the grain. Dormancy progressively disappeared during natural drying, at a slower rate for grains developing at 15°C than for grains developing at 25°C. However, at both temperatures, the release from dormancy was complete at maturity. In Scipion grain, dormancy was almost total throughout grain development irrespective of the temperature. However, grains could germinate in the presence of fluridone: changes in sensitivity to fluridone were observed during grain development, showing an increase in dormancy during the first half of development, followed by a progressive decrease during the second half. This decrease occurred later for grains developing at 15°C than for those developing at 25°C. In Scipion grain, unlike the cultivar Recital, release from dormancy was not completed before the end of development on the mother plant. An additional dry storage period was necessary which was shorter for grains developed at 25°C than for grains produced at 15°C. A comparison of embryo ABA levels after a 24-h culture in the presence or absence of fluridone, allowed the ABA synthesis to be estimated. It appears that the depth of dormancy was related to the estimated ABA synthesis capacity of the embryos.

Seed morphology and physical dormancy of several North AmericanRhusspecies (Anacardiaceae)

AbstractSeed (= seed plus endocarp) morphology and physical dormancy were studied in seven North AmericanRhusspecies:R.copallina,R.glabra,R.typhina,R.aromatica(var.aromatica),R.microphylla,R.trilobata, andR.virens(var.virens). Seeds ofRhus glabraandR.typhina, of subgenusRhus, were gray, approx. 3 mm long, 2 mm wide, and weighed approx. 7 mg, whereas those ofR.aromatica,R.trilobata, andR.virens, of subgenusLobadium, were brown, >4 mm long, approx. 4 mm wide, and weighed approx. 14.5 mg (R.trilobata) to approx. 23 mg (R.aromaticaandR.virens). Dormancy in all seeds was due to a water-impermeable endocarp, but depth of dormancy varied greatly among species and seedlots. After 4 weeks, 29–34% of the seeds from all five seedlots ofR.trilobata,R.microphylla, andR.virensincubated on moist substrate had imbibed, compared to 0–14% of the seeds of all 16 seedlots ofR.aromatica,R.copallina,R.glabra, andR.typhina. After 1 yr, imbibition among seedlots ofR.aromaticavaried from 28 ± 2% to 69 ± 5%, whereas 93 ±2% to 100 ± 0% of the seeds from all seedlots ofR.microphylla,R.trilobata, andR.virensdid so. Neither dry laboratory storage for up to 4 yr (even 29 yr inR.aromatica) nor dry heating at 100oC or at 120oC effectively broke dormancy in any of the species tested (R.aromatica,R.glabra,R.trilobata,R.virens). Immersion in boiling water was the best method to render seeds ofR.glabraandR.typhinapermeable, yet it was ineffective for those ofR.aromatica,R.trilobata, andR.virens. In contrast, a 1 h-soaking in concentrated H2SO4led to complete loss of endocarp impermeability in the latter three species, but mostly was ineffective inR.glabraandR.typhina. Thus, there seems to be a tendency for seeds of subgenusRhusto respond well to boiling in water, but not to soaking in H2SO4, whereas the opposite is true for those of subgenusLobadium.

Involvement of abscisic acid (ABA) in bulb dormancy of Allium wakegi Araki I. Endogenous levels of ABA in relation to bulb dormancy and effects of exogenous ABA and fluridone

Allium wakegi plants exposed to long days (LD, 14 h-photoperiod) developed bulbs, which were dormant from the 30th to the 125th day of LD, but those grown under natural short days (SD) did not develop bulbs. The contents of abscisic acid (ABA) in both whole bulbs and buds of the bulbs increased in LD, reaching a maximum at the 60th day of LD and decreasing thereafter, but those in basal leaf sheaths (this part corresponds to a bulb after bulb development) and buds did not increase in SD. The ABA content was related to the depth of bulb dormancy. Application of 500 μM ABA to bulbs for 24 h significantly delayed sprouting, but that of 5 or 50 μM ABA had little or no effect. Application of 25 or 125 μM fluridone to the soil just before exposure to LD bleached new expanding leaves and reduced bulb size, but had no effect on the development of bulb scales that characterize bulb formation. The bulbs formed under such conditions sprouted earlier than those of control plants. The levels of endogenous ABA in bulbs, buds of the bulbs, leaf blades, and roots were reduced by fluridone application. These results indicate that ABA plays an important role in bulb dormancy of Allium wakegi.

Water Status in Relation to Maintenance and Release from Dormancy in Blueberry Flower Buds

Three blueberry (Vaccinium section Cyanococcus) genotypes, that have different chilling requirements and levels of cold hardiness, were studied. Depth of dormancy was evaluated and water status was determined, using nuclear magnetic resonance (NMR), throughout the accumulation of chilling that leads to release from dormancy. Among the two highbush cultivars studied, `Bluecrop' (Vaccinium corymbosum L.) was the most dormant and `Gulfcoast' (Vaccinium corymbosum L. x Vaccinium darrowi Camp) was the least dormant. The rabbiteye cultivar `Tifblue' (Vaccinium ashei Reade) had an intermediate dormancy. It appeared that the cultivar with the deepest dormancy had also the highest chilling requirement (CR). The NMR results showed that `Bluecrop' buds had the lowest relaxation times (T2), indicating that water was relatively more bound in `Bluecrop' buds than in the buds of the two other cultivars. Whatever the cultivar, no significant variation of T2s and water content of the buds was noted throughout the accumulation of chilling, even after CRs were satisfied. Within 1 day of forcing (24 °C, long day), there was a shift towards freer water but no change in the water content. Forcing was ineffective in freeing water until the plants received enough chilling to satisfy their CRs.

テッポウユリにおける低温処理後の不発芽発生と球根の休眠程度ならびに貯蔵法との関係

The present experiments were carried out to determine the relationship between depth of dormancy and sleeper occurrence after chilling, and also to know factors involved in sleeper occurrence, using 'Hinomoto'. Bulbs, 19 to 22 cm in circumference were planted at different times of the season and sprouted at 10, 15, 20, and 25 °C to determine the depth of dormancy. To determine sleeper occurrence, bulbs were vernalized at 9 °C for 6 weeks at different intervals after harvest and allowed to sprout at prevailing summer temperatures (20 to 30 °C) or at 25 °C.Bulbs which were planted later in the season sprouted at a higher percentage frequency and quicker at 15 °C and 20 °C. This sprouting pattern indicated that the depth of dormancy decreased with increasing storage period at room temperature after harvest.A high percentage of bulbs sprouted if chilled immediately after harvest. The sprouting percentage decreased markedly when bulbs were chilled after dry storage at room temperature for 1 to 3 weeks. When the chilling was delayed, the sprouting percentage improved.Most bulbs that were stored dry at 20 to 30 °C for 2 weeks and then chilled, did not sprout and became sleeper; bulbs vernalized without dry storage had a high sprouting percentage.Soaking bulbs in 47-48 °C water for 1 hour immediately after harvest accerelated sprouting at 20 °C; dry stored, chilled bulbs also had a high sprouting percentage following the hot water treatment.These results indicate that there is no relationship between depth of dormancy and sleeper occurrence and that dry storage of bulbs at 20 to 30 °C for 1 to 3 weeks after harvest in June induced occurrence of sleepers after subjecting to chilling

Responsiveness of Amaranthus retroflexus seeds to ethephon, 1-aminocyclopropane 1-carboxylic acid and gibberellic acid in relation to temperature and dormancy

Dormant Amaranthus retroflexus seeds do not germinate in the dark at temperatures below 35°C. Fully dormant seeds germinate only at 35–40°C whereas non-dormant ones germinate within a wider range of temperatures (15 to 40°C). Germination of non-dormant seeds requires at least 10% oxygen, but the sensitivity of seeds to oxygen deprivation increases with increasing depth of dormancy. 10−6 to 10−4M ethephon, 10−3M 1-aminocyclopropane 1-carboxylic acid (ACC) and 10−3M gibberellic acid (GA3) break this dormancy. In the presence of 10−3M GA3 dormant seeds are able to germinate in the same range of temperatures as non-dormant seeds. The stimulatory effect of GA3 is less dependent on temperature than that of ethephon, while ACC stimulates germination only at relatively high temperatures (25–30°C). The results obtained are discussed in relation to the possible involvement of endogenous ethylene in the regulation of germination of A. retroflexus seeds.

Changes in dormancy levels ofFraxinus excelsior L. embryos at different stages of morphological and physiological maturity

The dormancy status ofFraxinus excelsior embryos at different developmental stages under environmental conditions was examined over a period of 2 years. For each sampling date the length of the fruit, of the seed, and of the embryo were measured, and the embryological stage determined. The depth of dormancy was assayed by the germination behaviour of isolated embryos under aseptic conditions on an agar medium without nutrients. As an approach towards a quantitative estimate of the dormancy status, the degree of inhibiton of germinative growth in the embryonic organs was evaluated on the basis of four categories from none to full germinative growth. From these ratings a dormancy index was calculated, expressing the mean dormancy status of the embryos at a given date. Embryo dormancy already became apparent during embryogenesis and reached its highest level during the later phase of reserve deposition in the seed. A marked loss of embryo dormancy occurred during the phase of maturation drying in autumn, followed by a moderate increase in winter. In hydrated seeds in spring the embryo was gradually released from dormancy and enlarged further. In maintaining the embryo ofF. excelsior in a developmental but not germinative mode, dormancy mechanisms within the embryo and the endosperm, combined with environmental factors, may be involved.

Changes in Abscisic Acid Content and Water Status in Bulbs of Allium wakegi Araki throughout the Year.

Changes in abscisic acid (ABA) content and water status in bulbs of Allium wakegi were investigated throughout the year. The life cycle of A. wakegi was divided into a nonbulbing period (from October 1 to March 15), a bulb developing period (from April 1 to May 15) and an established bulb period (from June 1 to September 15) ; it was divided in a dormant period (from April 1 to August 15) and an active growth period (from September 1 to March 15)ABA content in bulbs increased during the bulb developing period and then tended to decrease during the established bulb period. In the non-bulbing period ABA content was relatively low. Water potential decreased in the bulb developing period, was remained low during the established bulb period and then rapidly increased just after planting. Pressure potential in bulbs tended to be higher in the non-bulbing period than in the established bulb period. The innermost scales had the highest ABA content. during the different stages of bulb development.During the non-bulbing and bulb developing period, there was a significant inverse correlation between ABA content and pressure potential in bulbs. This is interpreted that the changes in water status is associated with an increased ABA content during the bulb developing period; however, the correlation was poor during the established bulb period. During the dormant period, there was a positive correlation between ABA content and the depth of dormancy although the time of deepest dormancy (May 1) did not coincide with the maximum ABA content (June 1). From these results, it is suggested that bulb development is accompanied by a change of water status which induces accumulation of ABA and that ABA is involved in bulb dormancy.

Actions of acid immersion, red light and gibberellin A 3 treatments on germination of thermodormant lettuce seeds

Lactuca sativa cv. Grand Rapids seeds not exposed to dark storage at 30°C (DS) germinated completely at 20°C with red light (R) or 0.5 mM gibberellin A 3 (GA 3) regardless of pretreatment of R, far-red light (FR) or 1-hr acid immersion (pH 0.1) plus water rinse (H +). H + treatment alone increased germination of FR-treated seeds from 16 to 50%. GA 3 had little effect on FR-treated seeds held in DS for between 18 hr and 10 days. Promotion of germination by R decreased slowly with increased DS time and finally disappeared, indicating the induction of thermodormancy. Seeds rendered thermodormant by 10–30-day DS did not germinate with water alone, but germinated 8% or less following R, GA 3 or H + treatment. These thermodormant seeds germinated 85% or more if H + was given before R or GA 3. Thermodormant seeds, which revealed R on days 0, 10 or 20 of DS, germinated 83–90% if given only H + treatment. GA 3 caused higher germination at 20°C in R-pretreated thermodormant seeds than R, indicating synergism between GA 3 and R. The R pretreatment reduced the degree of thermodormancy and also dark reversion of P fr (FR-absorbing form of phytochrome). It is suggested that P fr cannot induce germination in thermodormant seeds although some P fr presists for up to 30 days DS. P fr can function in these thermodormant seeds only when they are given an H + treatment. It is concluded that thermodormant seeds incubated in darkness at 30°C are similar to skotodormant seeds incubated in darkness at 20°C, but the depth of secondary dormancy in the former is deeper. Presumably P fr loss is accelerated at higher temperature.

Effects of Storage Temperatures and Duration on the Performance of Bareroot Deciduous Hardwood Trees

Two-year-old Norway maple (Acerplatanoides), red oak (Quercus rubra), European mountain ash (Sorbus aucuparia), paper birch (Betula papyrifera), and Washington hawthorn (Crataegus phaenopyrum) seedlings were stored bare-root at temperatures of +4, 0 -2, and -4C for 0, 3, or 6 months. Survival and regrowth of plants stored at 0, -2, or -4C was better than at +4C. Survival, root regrowth, and % budbreak were maintained at pre-storage levels when Norway maple, red oak, European mountain ash, and paper birch were stored at -4C, and when Washington hawthorn was stored at -2C. Among the species tested, Norway maple and European mountain ash appeared most tolerant, red oak slightly less tolerant, and paper birch and Washington hawthorn the least tolerant of postharvest cold storage. Among Norway maple, red oak, and Washington hawthorn, tolerance to postharvest handling conditions appeared to be related to the depth of dormancy and a lower natural xylem water potential during the winter season. Increasing the length of time in storage reduced root regrowth and % budbreak, and increased plant mortality, stem dieback and the number of days to budbreak for most species stored at all test temperatures.

Changes in photosynthetic activity of buds and stem tissues of Fagus sylvatica during winter

The photosynthetic activity of leafless twigs and buds of Fagus sylvatica was determined by in vivo chlorophyll fluorescence from November to May. Measurements were made on the day of sampling, and during exposure to warm temperatures until reactivation was attained. Under the same conditions, bud development and growth were forced by exposure of cut twigs to 25/18° C at long-day conditions, and bud swelling and bud burst were monitored. Winter inactivation of photosynthesis results in a reduction of the photochemical efficiency of PS II, as indicated by lowering of FV/FM, from January through March. The greatest reduction is in cortical chlorenchyma, the least in folded leaflets and primordia of buds. Restoration of photosynthetic activity, brought about by warming, needed 3–4 weeks in cortex and 1–2 weeks in buds during the coldest period of winter. Frequency distributions based on three types of chlorophyll fluorescence transients, defined by quantitative fluorescence parameters, have proved to be a valuable method for a differentiated expression of the unequal functional activation states of parallel samples. The seasonal course of winter inactivation of photosynthesis did not correspond entirely with the depth of bud dormancy as revealed by the forcing treatments; inactivation of photosynthesis may be more closely synchronized with changes in frost hardiness; possible causes are discussed. We suggest, therefore, that a distinction should be made between inactivation of metabolic processes and depth of dormancy, even though these processes are inherently interrelated.

Seasonal Variation in Intensity of Bud Dormancy in Apple Cultivars and Related Malus Species

Dormancy patterns throughout the season were studied in more than 90 apple (Malus ×domestica Borkh.) cultivars and related Malus spp. The seasonal apple bud dormancy pattern resembles a normal curve: it starts to intensify soon after bud formation and reaches maximum intensity by the time of leaf fall/senescence. Genotypes were grouped into three general classes based on maximum dormancy intensity. Maximum intensity of bud dormancy measured in cold winters is inversely related to adaptation to the subtropics. Low-chilling requirement (CR) cultivars have a shallow depth of dormancy with very little alteration throughout the year. High-CR cultivars have intense bud dormancy, the first stage of which can be induced by growing these cultivars at temperatures above 20C. Genotypes differed in their rates of dormancy dissipation. The efficiency of chilling unit (CU) accumulation to break dormancy was negatively correlated with CR, which indicates the importance of factors other than CU accumulation in terminating bud dormancy in low-CR cultivars. The inherent length of bud dormancy plays a major role in determining the time of budbreak in the spring. Deviations may be related to the genotypic efficiency in which chilling modifies dormancy and possibly the basal temperatures to which buds respond. Chill unit requirement and heat unit requirement are dependent factors. Heat requirement comparisons may be meaningless if the dormancy intensities of the genotypes are not taken into consideration.

Effect of Defoliation Time on Depth of Dormancy and Bloom Time for Low-chill Peaches

In a relatively low-chill environment, two cultivars of peach [Prunus persica (L.) Batsch] differing in chilling requirement (`Flordaprince', 150 units and `Flordagold', 325 units) were defoliated at 10-day intervals during midautumn. Effects of defoliation on depth of bud dormancy and dose-dependent responses of cuttings to hydrogen cyanamide throughout the dormant period were analyzed to develop a dormancy index (DI). DI values indicate that early defoliation reduces depth of bud dormancy throughout winter for both cultivars. For `Flordaprince', this was translated into early leafing and bloom, but fruit size was reduced by early relative to late defoliation. In contrast to `Flordaprince', vegetative and floral budbreak of `Flordagold' were delayed by early defoliation. These results indicate that early defoliation affects depth of dormancy and growth ability of buds, but that the extent to which these factors affect bud development depends on cultivar.

カキ茎頂の <i>in vitro</i> のサイトカイニン反応性とその季節的変化

To determine the best season for shoot tip culture of Japanese persimmon, shoot tips were cultured monthly from February 1987 to January 1988 in 1/2N-MS basal medium, Murashige and Skoog′s medium containing half strength nitrogen, with zeatin. No shoot growth was observed in the medium without zeatin. In any month of the year, the shoot growth was enhanced by 10-5M zeatin. The activity of shoot tips in shoot elongation increased from late April to late June, and shoot length after six weeks of culture was maximum on 22 June. Thereafter, activity decreased until late October and then remained constant until early April. These changes in shoot growth in vitro coincided with the changes of depth of internal dormancy. Leaf number was high in 10-5M zeatin only on 30 May and 22 June. From principal component analysis using four growth characteristics for the medium with 10-5M zeatin, the first principal component score in June was the largest of the year. Shoot tip growth in June had, therefore, better shoot elongation, leaf differentiation, callus formation and mortality rate, so the appropriate season for shoot tip culture of Japanese persimmon was considered to be June.

Energy charge during aerobic and anaerobic imbibition of Kalanchoë blossfeldiana seeds

Abstract Adenosine phosphate levels were measured in Kalanchoë blossfeldiana cv. feuerblüte seeds during dark imbibition in aerobic and anaerobic conditions. A correlation between the depth of primary dormancy (light requirement) and the increase of ATP‐content during the first hours of aerobic imbibition was found, but the rise of energy charge from about 0.2 in dry seeds to 0.8 after 18 h is not related to the breaking of dormancy and consequently to germination. In an anaerobic environment, the increase in ATP‐content is dramatically lowered and the energy charge value stabilizes at about 0.4, most probably as the result of fermentation activity.