Studies on the Dormancy of Calluna vulgaris (L.) Hull, during Winter: The Effect of Photoperiod and Temperature on the Induction of Dormancy and the Annual Cycle of Development

The effects of daylength and temperature on the induction ofdormancy in shoots of Calluna vulgaris were investigated usingcontrolled environment growth rooms. Short days did not induce dormancy in Calluna but floweringwas inhibited and shoots having a characteristic end-of-seasonmorphology were formed. Short days combined with low temperaturesarrested growth but the depth of dormancy was not as great asthat of plants in the field in late autumn. Long days combinedwith low temperature did not induce dormancy or the end-of-seasonmorphology. Results from the growth room experiments may be interpretedin relation to the annual cycle of development of Calluna underfield conditions. Calluna vulgaris (L.), photoperiod, temperature, dormancy, flowering, annual cycle of development     

Influence of Nitrogen and Winter Climate Stresses on Calluna vulgaris(L.) Hull

Four nitrogen (N) levels, spanning those found naturally, wereestablished in Calluna vulgaris grown in containers in an oceanicclimate for 4 years on the southwest coast of Norway. EstablishedN contents of the plants were 0.7, 0.8, 1.3 and 2.5% of dryweight. Experiments comprising 5000 plants were performed inthe open and in growth chambers. In the open, dry matter accumulationand date of bud burst were recorded at the different N levels.Breaking of winter dormancy was studied under controlled conditions.In October/November, plants needed 1474 day-degrees for budburst at the lowest N level, whereas at the highest level only582 day-degrees were required. The natural start of growth inthe field was on 14 April at the highest N level and on 26 Aprilat the lowest. Freeze testing of the shoots (with the rootsprotected from frost) revealed that Calluna tolerates temperaturesas low as -15 °C as late as the beginning of April. However,plants at the two medium N levels were most tolerant of frost.During the last winter of the experiments, nearly 50% of plantsin the open died at the highest N level, whereas plants at thelower levels survived without damage. The effects of N are discussedin relation to the influence on physiological ageing of theplants, the change in nutrient balance of the plant tissue andthe subsequent increase in susceptibility to biotic and abioticstresses. Copyright 2001 Annals of Botany Company Calluna vulgaris, climate stress, growth initiation, nitrogen     

Bud Dormancy in the Kiwi Fruit, Actinidia chinensis Planch

A study of lateral bud dormancy in Actinidia chinensis has shownthat true dormancy can be induced, especially in short daysat warm and constant temperatures This dormancy can be brokenquantitatively by chilling but temperatures as high as 10 °Care effective The dormancy appears to be due to an inhibitor(possibly ABA), apparently stored in the special bud cover aspecial structure in Kiwi fruit which may represent fused stipulesRemoval of the cover also admits oxygen and light, both of whichhave promoting effects on bud break Application of ABA enhancesdormancy (as do crude extracts tentatively identified as ABA)while GA₃ application enhances dormancy before chilling andpromotes bud break only after chilling Actinidia chinensis, Kiwi fruit, dormancy, abscissic acid, gibberellic acid, chilling     

Determination of the Pattern of Winter Dormancy in Lateral Buds of Apples

Controlled environmental conditions and decapitation treatmentswere used to distinguish and determine the relative importanceof environmentally-imposed dormancy, correlative inhibitionand rest on the imposition of winter dormancy of lateral budson detached shoots and potted seedlings of apples. It is establishedthat the winter dormancy of lateral buds follows a pattern similarto that previously proposed for buds in general. The minimum procedure for the assessment of dormancy in lateralbuds is discussed. Malus sylvestris L, apple, bud dormancy, winter dormancy     

Breaking of Seed Dormancy by Nitrate as a Gap Detection Mechanism

Germination of Planlago lanceolata seeds buried in a chalk grasslandwas higher in bare soil than in vegetated soil, and measurementof soil nitrate concentrations showed that they were high enoughto account for this stimulation. When seeds of P. lanceolatawere sown in pots of soil with or without plants, and wateredwith nutrient solution containing either no nitrate, or 14 mMnitrate (sufficiently high that not all nitrate was absorbedby the plants), the presence of plants inhibited germinationonly when the nutrient solution contained no nitrate. It wasconcluded that breaking of seed dormancy by nitrate can functionas a gap detection mechanism if nitrate concentrations in baresoil are high enough to break seed dormancy, but are too lowto break dormancy when vegetation is present Plantago lanceolata, seed, dormancy, germination, nitrate, gap detection     

Changes in Dormancy and Sensitivity to Vernalization in Axillary Buds of Satsuma Mandarin Examined in vitro During the Annual Cycle

Effect of season and the presence of fruit on bud-endodormancyand the flowering response to low temperature treatments weredetermined using bud cultures of Owari satsuma mandarin (Citrusunshiu Marc). Bud dormancy was deeper in fruiting as comparedto defruited trees. In fruiting trees, the intensity of buddormancy was highest in spring, decreased to a low value byearly Jul. and then increased until early winter. This increasein dormancy during summer and early autumn did not occur innon-fruiting trees. No flowers formed in buds cultured betweenMay and Sep. Both in fruiting and defruited trees, buds becamecompetent to show a vernalization response to chilling by theend of Oct., at the time they also became capable of sproutingin vitro at low temperature (15/10 °C). There was a directeffect of fruit on the buds which persisted long after fruitremoval and resulted in a reduction of the flowering responseto chilling.Copyright 1995, 1999 Academic Press Citrus flowering, Citrus unshiu Marc., dormancy, flower induction, flowering, in vitro flowering, satsuma mandarin, vernalization     

The Development and Emergence of Buds in Phragmites communis Trin.

Phragmites communis rhizomes grow during the autumn, but budsdevelop nearly all the year round. For much of the year thebuds remain dormant near the soil surface, and then in springthere is a period of rapid emergence which lasts from betweena few weeks to nearly 4 months. Apart from replacements of frost-killedshoots, few buds emerge during the rest of the year. Emergencestarts at the end of the period of internal dormancy if theweather is warm enough. In Britain it is not, and there is abouta month of temperature-controlled dormancy. Emergence can bedelayed further by unusually unfavourable conditions of temperatureor water-supply. Exposure to frost kills some shoots, but stimulates bud developmentand lengthens the emergence period. Burning and severence ofrhizomes break internal dormancy. Cutting does not, and so isvery damaging if carried out directly after the emergence period,since no replacement crop is then produced, and so that plantis unable to photosynthesize during half of the growing season.     

Intensity of Bud Dormancy in Douglas-fir and Its Relation to Scale Removal and Rooting Ability

Uniform 1- or 2-year-old rooted cuttings of 3 Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, clones were grown under natural conditions in containers from July 1, 1971 to February 15, 1972. At 2-week intervals, plants from this natural temperature and daylength environment were moved into controlled, long day (LD-18 h) and short day (SD-9 h) environments to measure the intensity of bud dormancy from its inception to termination based on number of days to bud break and percentage of expanding buds on a given date. Growth responses to bud scale removal were also helpful in describing the degree and nature of bud dormancy. The cessation of initiatory activity at the bud apex, reflected in the needle number of the subsequent growth flush, corresponded to a September peak of bud dormancy based on the number of days to bud break in the LD environment. Similarly, the cold requirement for breaking bud dormancy was measurable in the SD environment. The use of such rest intensity indices is illustrated in the close relationship established between bud dormancy development and stem cutting rooting ability.     

An Examination of some Symbiotic Systems for Fixation of Nitrogen

By the use of ¹⁵N the occurrence of fixation of elemental nitrogenhas been demonstrated in the lichens Collema granosum and Leptogiumlichenoides (both of which contain Nostoc as a symbiont), andalso in the liverwort Blasia pusilla (which has Nostoc-containingcavities in the thallus). The circumstances indicate that thefixation in these instances should be attributed to the Nostoc. No evidence of fixation was obtained in similar isotopic testson the mycorrhizal roots of intact plants of Calluna vulgarisand of Pinus sylvestris, although these, more especially inthe case of Calluna, have been held by some previous authorsto be nitrogen-fixing.     

Changes in Protein Profiles of Poplar Tissues during the Induction of Bud Dormancy by Short-Day Photoperiods

Vegetative bud dormancy in woody perennial plants of the temperateregions is an important adaptive strategy for withstanding lowwinter temperatures. We used shortday (SD) photoperiods to inducebud dormancy in poplar (Populus deltoides Bartr. ex Marsh.),and characterized changes in protein profiles during dormancydevelopment. Short days alone, under warm temperatures (25°C)induced a high level of dormancy comparable to that developednaturally. Under SD conditions the amounts of acetone/trichloroaceticacid (TCA)-insoluble dry powder (DP) increased in terminal andlateral buds, leaves and bark tissues. The total protein contentin DP from buds and leaves steadily decreased while total proteinfrom bark increased. The 2-dimensional (2-D) PAGE analyses showedthat terminal and lateral buds responded similarly to SD. Fourpolypeptides that newly appeared or increased in abundance andfive that disappeared or diminished in terminal buds during10 weeks of treatment were also detected in lateral buds. Twoof these newly apparent polypeptides were also found in bark.Similar polypeptides were not found in leaves. Changes in proteinmetabolism and possibly altered gene expression might be importantpart in the overall response of poplar to SD during dormancydevelopment. This is Oregon Agricultural Experimental Station Technical PaperNumber 1122.     

Dormancy of alpine and subalpine perennial forbs

Depth of dormancy of alpine and subalpine perennial forbs in autumn was investigated, which was judged by the number of days required for growth initiation at 24 °C. The depth of dormancy differed depending on Raunkiaer’s life-form and shoot habits. Chamaephytes with perennial shoot-axes showed shallower dormancy than hemicryptophytes with annual shoot-axes, and geophytes with annual shoot-axes showed the deepest dormancy. The results strongly suggest that the dormancy is more endogenously controlled in forbs less hardy to freezing stress. Potential growth ability of alpine herbaceous chamaephytes in autumn is an adaptive advantage, since they utilize the short vegetative period as long as possible. All of the species with annual shoot-axes had winter buds covered with scales. In plants with perennial shoot-axes, percentage of winter buds covered with scales increased with increasing depth of dormancy. The results indicate that the shoot apices are well protected by bud scales in forbs with a long endogeneous-dormant period.     

Ecotype-dependent control of growth,dormancy and freezing tolerance under seasonal changes in <Emphasis Type="Italic">Betula pendula</Emphasis> Roth

Woody plants in the temperate and boreal zone undergo annual cycle of growth and dormancy under seasonal changes. Growth cessation and dormancy induction in autumn are prerequisites for the development of substantial cold hardiness in winter. During evolution, woody plants have developed different ecotypes that are closely adapted to the local climatic conditions. In this study, we employed distinct photoperiodic ecotypes of silver birch (Betula pendula Roth) to elucidate differences in these adaptive responses under seasonal changes. In all ecotypes, short day photoperiod (SD) initiated growth cessation and dormancy development, and induced cold acclimation. Subsequent low temperature (LT) exposure significantly enhanced freezing tolerance but removed bud dormancy. Our results suggested that dormancy and freezing tolerance might partially overlap under SD, but these two processes were regulated by different mechanisms and pathways under LT. Endogenous abscisic acid (ABA) levels were also altered under seasonal changes; the ABA level was low during the growing season, then increased in autumn, and decreased in winter. Compared with the southern ecotype, the northern ecotype was more responsive to seasonal changes, resulting in earlier growth cessation, cold acclimation and dormancy development in autumn, higher freezing tolerance and faster dormancy release in winter, and earlier bud flush and growth initiation in spring. In addition, although there was no significant ecotypic difference in ABA level during growing season, the rates and degrees of ABA alterations were different between the ecotypes in autumn and winter, and could be related to ecotypic differences in dormancy and freezing tolerance.     

Abscisic Acid Analysis in Vitis vinifera in the Period of Endogenous Bud Dormancy by High Pressure Liquid Chromatography

In buds and nodes of Vitis vinifera L. cv. Riesling, the content of abscisic acid (ABA) was measured by high pressure liquid chromatography and related to bud dormancy. In the period of endogenous bud dormancy (rate of bud break is low or zero under favourable climatic conditions) the ABA content increased twelvefold. This indicates a causal relationship between endogenous bud dormancy and ABA.     

High temperatures applied at fall forcing disturb ovule development in Syringa vulgaris L. “Mme Florent Stepman”

Under natural conditions, Syringa vulgaris blooms in May but it may be forced to produce blooming panicles in autumn, winter and early spring. To break winter dormancy, plants require high temperatures, the range of which depends on the forcing date. Forcing in November requires exposure to temperatures of ∼37°C. Such an exposure may affect the development of both male and female flower organs. In this work we have followed the anatomical changes in the ovule development in buds collected from plants forced in autumn, and compared them to those in plants blooming under natural conditions in May. From the earliest identifiable stages, in flowers forced in November the ovule development was delayed relative to the normal development pattern. Ultimately, most of the ovules (83%) degenerated before the differentiation of the embryo sacs was completed. We believe that it is the high temperatures required during autumn forcing that affect the development of female gametophytes, leading to the formation of defective structures which often degenerate. This in turn may reduce the esthetic appeal of the inflorescences and reduce their commercial value.     

Long-day Induced Dormancy in Anemone coronaria L

In Anemone coronaria L. summer dormancy in Israel can be inducedby long photoperiods even in the middle of the winter. Cultivationin Europe has reduced but not eliminated this response to daylength.Daylength did not affect the time of flowering but dormancycaused early cessation of flowering under long days. Anothereffect of long-day treatment was to produce longer scapes. Anemone coronaria, summer dormancy, long-day induction, daylength response     

Long-Day Induced Bud Break in Salix pentandra Is Associated with Transiently Elevated Levels of GA1 and Gradual Increase in Indole-3-Acetic Acid

Initiation of dormancy in woody species is induced by a shortphotoperiod. In the early stages of dormancy development, growthcan be initiated by long days. To study the possible involvementof gibberellins and indole-3-acetic acid in bud break in Salixpentandra, effects on levels of these plant hormones of transferof seedlings in an early stage of dormancy to a growth-inductivelong photoperiod was investigated. The bud break and initiationof growth correlated with a rapid transient increase in GA₁in defined zones of shoot tips to levels twice of that in continuouslyelongating long day-grown control seedlings, followed by a rapiddecrease to levels similar to in these control plants. Also,the contents of GA₅₃, GA₁₉, GA₂₀, GA₈ increased upon transferfrom short to long days. Levels of indole-3-acetic acid showeda gradual decline under short days, and increased graduallyupon transfer to long days up to a level of continuously elongatingplants. The present data suggest an interaction between gibberellinand indole-3-acetic acid in the photoperiodic control of dormancydevelopment and bud break in S. pentandra. (Received October 14, 1996; Accepted February 18, 1997)     

Environmental Factors Influencing the Expression of Dormancy Patterns in Weed Seeds

Buried seeds often show seasonal periodicity of dormancy. Dormancypatterns of Chenopodium album, Polygonum persicaria, Sisymbriumofficinale and Spergula arvensis were studied by burying seedsunder field conditions in sandy loam in December, 1986. Seedswere exhumed at regular intervals and germination was subsequentlytested in the laboratory. It was shown that the conditions ofthe germination test influenced the expression of the dormancypattern. Germination of C. album and 5. arvensis always dependedon the presence of light, whereas seeds of S. officinale completelylost their light dependency during the first winter. Applicationof nitrate during the germination test in light improved germinationof all species. Dark germination was not stimulated by nitratealone. Desiccation of the exhumed seeds at a r.h. of approx.15% enhanced germination under all conditions. A combinationof several stimulating factors revealed breaking of dormancymuch earlier in the season. During induction of secondary dormancythe effect of the test conditions was even more pronounced.Dormancy induction could be overlooked for several months whenseeds were desiccated and/or given nitrate during the germinationtest in light. It is hypothesized that in the field both desiccation- due to cultivation and dry spells - and nitrate enrichmentof the soil will influence the expression of the seasonal patternof dormancy and therefore enlarge the period of possible seedlingemergence Desiccation, dormancy pattern, germination, light, nitrate, seeds, weeds, Chenopodium album, Polygonum persicaria, Sisymbrium officinale, Spergula arvensis     

Growth and Dormancy in Lunularia cruciata (L.) Dum: V. THE CONTROL OF GROWTH BY A NATCRAL, ENDOGENOUS INHIBITOR

The production of an endogenous growth inhibitor by Lunulariahas been demonstrated in tests with diffusates from gemmae andthalli. Increased growth made by bisected gemmae compared withintact controls suggests that self-inhibition also occurs andpoints to the growing tip as the locus of inhibitor production.More inhibitor is produced in short-day (optimum growth) thanin long-day (dormancy inducing) conditions, but even in shortdays the growth of thalli depends on conditions allowing theinhibitor to diffuse away. Thalli prevented from doing thisby resting the apical 2 mm on non-wettable cover slips stoppedgrowth and showed morphological changes of incipient dormancy.Some of the ecological implications of these tests are discussed.     

Dormancy of the barley grain is correlated with gibberellic Acid responsiveness of the isolated aleurone layer

The relationship between barley grain dormancy and gibberellic acid (GA₃) responsiveness of aleurone layers has been investigated. Barley (Hordeum distichum L. cvs Triumph and Kristina) grains were matured under defined conditions in a phytotron. Grains of Triumph plants grown under long-day/warm conditions had lower dormancy levels than grains of plants grown under short-day/cool conditions. Aleurone layers isolated from grains of long-day Triumph plants secreted more α-amylase and had a higher responsiveness to GA₃ as measured by α-amylase secretion. Storage of the grains increased both the percentage of germination and the responsiveness of the aleurone to GA₃. Use of different sterilization methods to break dormancy confirmed the correlation between germination percentage and aleurone layer GA₃ responsiveness. The response of embryoless Triumph grains to GA₃ was lower than that of the isolated aleurone layers, suggesting a role of the starchy endosperm in regulating the GA₃ response of the aleurone layer. Grains of the cultivar Kristina harvested from short day- and long day-grown plants lacked dormancy, and their isolated aleurone layers had a similar responsiveness to GA₃ as measured by α-amylase secretion. The data indicate that the physiological state of the aleurone layers contributes to the percentage germination of the grains.     

Variation within species and inter-species comparison of seed dormancy and germination of four annual Lamium species

In an ecological context, knowledge of intra-species variation in dormancy and germination is necessary both for practical and theoretical reasons. We used four or five seed batches (replicates) of four closely related annuals co-occurring in arable fields in Sweden: Lamium amplexicaule, L. confertum, L. hybridum and L. purpureum. Seeds used for experiments stemmed from plants cultivated on two sites, each site harbouring one population of each species, thereby ensuring similar environmental history of seeds. Seeds were tested for germination when fresh and after three different pre-treatments (cold or warm stratification, or dry storage) for up to 24 weeks. Seeds were also sown outdoors. Despite substantial intra-species variation, there were clear differences between species. The general seed dormancy pattern, i.e. which environmental circumstances that affect dormancy, was similar for all species; dormancy reduction occurred during warm stratification or dry storage. Even though the response to warm stratification indicates a winter annual pattern, successful plants in Sweden were mostly spring emerged. Germination in autumn occurred, but plants survived winters poorly. Consequently, as cold stratification did not reduce dormancy, strong dormancy in combination with dormancy reduction during dry periods might explain spring germination. It is hypothesised that local adaptations occur through changes mainly in dormancy strength, i.e. how much effort is needed to reduce dormancy. Strong dormancy restricts the part of each seed batch that germinate during autumn, and thus reduces the risk of winter mortality, in Sweden.