The Influence of Ringing on Bud Development and Flowering in Satsuma Mandarin

Ringing of Satsuma mandarin (Citrus unshiu Marc.) trees showedincreased flowering in the following spring when performed duringSeptember and October, but not during November. Most of theeffect on flowering was due to an enhancement of both bud sproutingand the number of flowering shoots formed per node. In addition,a direct effect of ringing on flower initiation was demonstrated,since the number of vegetative shoots was reduced. The response of the buds to ringing was rapid as demonstratedby changes in bud weight, protein content, and electrophoreticpattern and behaviour when cultured in vitro. Buds from ringedtrees readily flowered in vitro when forced during the winterrest period and flower formation was enhanced by the additionof cytokinin. Buds from control trees formed a smaller numberof flowers in vitro, and flowering was much less enhanced bythe addition of cytokinin. It is concluded that ringing acceleratesflower initiation in the buds and this effect takes place beforethe winter rest period. Key words: Bud sprouting, Citrus unshiu Marc., flower initiation, flowering, in vitro flowering, Satsuma mandarin, ringing     

Photoperiodic Regulation of Flowering in Cowpeas (Vigna unguiculata (L.) Walp.)

To test the proposition that photoperiodic controls synchronizethe flowering of cowpeas, Vigna unguiculata (L.) Walp. [V. sinensis(L.) Savi], the day-length requirements for floral initiationand for flowering were investigated in several short-day accessions.No evidence was found of different critical photoperiods atdifferent stages of development, but exposure to only 2–4short days was required for floral initiation compared withabout 20 for development to open flowers. Pod setting was increasedafter exposure to even one short day more than the number requiredfor flower opening. Floral buds at higher nodes appeared to require fewer shortdays for development to flowering than buds at the lower nodes,and displayed faster rates of development. Inflorescence budsdid not resume development if they were exposed to 15 or morelong days following inflorescence initiation. Thus, any tendencytowards synchronous flowering in cowpeas is not due to the criticalday-length for flower development being shorter than that forflower initiation, but could be the result of cumulative photoperiodicinduction of plants and the more rapid development of later-formedflowers. Vigna unguiculata (L.) Walp., cowpeas, flower initiation, flower development, fruit set, photoperiodism     

FLOWER INITIATION IN TOTAL DARKNESS IN A QUANTITATIVE SHORT DAY PLANT, FAGOPYRUM ESCULENTUM MOENCH

The flowering behavior of two cultural varieties of Fagopyrumesculentum Moench aseptically cultured in total darkness wasstudied. The effect on the flower initiation of some chemicalsubstances added to sterilized dry seeds was also investigated.Low temperature was found to be more suitable for flower initiationin buckwheat plants. 2-Thiouracil promoted flower initiationat high temperature in total darkness and inhibited it at anytemperatures examined under light conditions. Sucrose promotedflower initiation at higher temperatures than 15. Lithium chlorideand peptone inhibited flower initiation only at high temperature.Indoleacetic acid, gibberellin and kinetin had no effect onflower initiation in total darkness. It is postulated that in the flowering response the primaryreaction may be connected with the metabolism of sucrose andribonucleic acid. (Received September 21, 1964; )     

Modelling the Masting Behaviour of Betula platyphylla var. japonica using the Resource Budget Model

A masting model of Betula platyphylla var. japonica, a majorwind-pollinated tree in Hokkaido, northern Japan, was constructedfrom the perspective of the resource budget model. An 11-yeardata series of pollen dispersal by birch showed marked annualfluctuations in flowering. Although flowering fluctuated widelyamong years, a reciprocal relationship was observed betweentwo consecutive years; very little flowering occurred aftera mast year. This suggests that there is a negative relationshipbetween current fruiting and flower bud induction. There wasa significant positive relationship in flowering between regions,which suggests that weather conditions regulate flowering inbirch. A model that included weather variables and resourceallocation systems among years explained 94·5% of theobserved annual fluctuations in flowering. In the model, warmspring conditions from bud burst to flower bud development andlittle flowering in the previous year (t-1) resulted in increasedflowering in the current year (t), whereas abundant floweringin year t-2 resulted in a decrease in flowering in the currentyear (t). The latter indicates that flowering in year t-2 affectsresource storage after overwintering; the balance is carriedforward to year t-1 and affects the initiation of flower primordiabefore bud burst. In the model, fluctuating weather conditionsin the previous spring strongly affected the masting behaviourof birch. Copyright 2001 Annals of Botany Company Betula platyphylla var. japonica, flowering, masting, modelling, pollen dispersal, resource allocation, resource budget model, weather conditions     

Apical Growth and Modification of the Development of Primordia During Re-flowering of Reverted Plants of Impatiens balsamina L

Impatiens balsamina L. was induced to flower by exposure to5 short days and then made to revert to vegetative growth byreturn to long days. After 9 long days reverted plants wereinduced to re-flower by returning them to short days. Petalinitiation began immediately and seven primordia already presentdeveloped into petals instead of into predominantly leaf-likeorgans. However, the arrangement of primordia at the shoot apex,their rate of initiation and size at initiation remained unchangedfrom the reverted apex, as did apical growth rate and the lengthof stem frusta at initiation. The more rapid flowering of thereverted plants than of plants when first induced, and the lackof change in apical growth pattern, imply that the revertedapices remain partially evoked, and that the apical growth patternand phyllotaxis typical of the flower, and already present inthe reverted plants, facilitate the transition to flower formation. Impatiens balsamina, flower reversion, partial evocation, shoot meristem, determination, leaf development     

Vegetative Proliferation of Floral Spikelets in British Grasses

Proliferation of spikelets in grasses other than those raceswhich are habitually viviparous is reviewed, and the factorsinducing proliferation experimentally in Cynosurus cristatusand other species are discussed. It is concluded that the evidencefavours the hypothesis that in the viviparous races a considerablygreater minimal concentration of the putative flowering hormoneis required for flower induction than for culm initiation, whereasin the seminiferous races this difference is not so great. Inthe viviparous races, the threshold for flower initiation israrely exceeded so that perfect flowers appear only occasionally,whilst in the normally seminiferous races, the conditions ariseonly rarely where an amount of hormone is produced sufficientto initiate culms but insufficient to promote flowering.     

Flower Formation from Citrus unshiu Buds Cultured In Vitro

Flowers were formed in vitro when buds of Satsuma mandarin (Citrusunshiu Mare) from the summer flush of growth harvested duringthe winter rest period before the onset of flower initiation,were grown on a solid Murashige and Skoog medium supplementedwith sucrose and a cytokinin. Flower development was dependentupon illumination, and was enhanced when a piece of stem wasattached to the bud. The percentage of flowering explants wasalways lower than the percentage of naturally flowering budsin spring, but treatments such as ringing which increase floweringin vitro, increased the number of explants flowering int vitroas well. Citrus unshiu Marc, ‘Satsuma’ mandarin, in vitro flowering, ringing     

Influence of Temperature and Photoperiod on Flowering and Tuberous Root Formation of Pachyrrhizus tuberosus

P. tuberosus, a native species of the Amazon region, was cultivatedunder different thermal regimes and photoperiods in an attemptto relate these stimuli to flower initiation and tuberous rootformation. It is shown that P. tuberosus is an intermediate-dayplant (flowers only under photoperiods above 9 h and below 16h). With regard to tuberization P. tuberosus may be considereda short-day plant: tuberization occurs only in photoperiodsbelow 16 h. High thermal regimes 30/25 C (13 h day/11 h night)delay and reduce flowering and completely inhibit tuberous rootformation. Thermal regimes of 25/20 C and 20/15 C (13 h day/11h night) were the most suitable for flowering and tuberization. Pachyrrhizus tuberosus, yam-bean, flowering, tuberization     

Mutant dn Influences Dry Matter Distribution, Assimilate Partitioning and Flowering in Lathyrus odoratus L.

The flowering mutant dn in sweet pea was used as a tool to study¹⁴C-assimilate and dry matter partitioning with respect to nutrientdiversion theories on the control of flower initiation. Wildtype plants (Dn^h) are photoperiodic and exhibit late floweringand profuse basal branching in short days while mutant plants(dn) are day neutral, early flowering and devoid of basal laterals.In short days, dn plants exported a significantly greater proportionof assimilate acropetally than (Dn^h) plants and the upper portionof dn plants had a greater dry weight. These differences werereduced dramatically when basal laterals were excised regularlyfrom the (Dn^h) plants although the difference in flowering remained.However, the effect of dn on resource allocation within theapical region may be more important in regard to flowering thanthe effect on acropetal versus basipetal movement. In shortdays, the dn plants partitioned significantly more resourcesinto their internodes and petioles, and less into their leaflets,than Dn^h plants as shown by dry weight and ¹⁴C-assimilate measurements.These differences were apparent from as early as node 7 up tothe node of flower initiation in dn plants (node 30) and theywere not eliminated by removal of basal laterals from Dn^h plants.Differences between dn and Dn^h plants in partitioning and floweringwere largely eliminated under long days. The fact that in thisspecies a single gene influences both resource allocation andflower initiation lends further support to nutrient diversionhypotheses on the control of flowering. Key words: Assimilate partitioning, branching, flowering, mutant, sweet pea     

Flower Development in Silene: Morphology and Sequence of Initiation of Primordia

The initiation and development of the flower of Silene coeli-rosawas followed by examining apices by scanning electron microscopy.The sepals, stamens and carpets are initiated in a spiral sequence,the direction of the spiral king the opposite of the acropetalhelix of unequal axillary buds at the nodes below the flower.The petals are initiated almost simultaneously and at the sametime as the first few stamens. The change in phyllotaxis fromopposite and decussate in the vegetative shoot to spiral inthe flower occurs with the displacement of the first two sepalsaway from the mid-line of the apex and towards the axillarybud at the node below the flower. The sizes of the sepals andstamens are a function of their age since initiation but thepetals grow more slowly. The Silene flower can be interpretedas a shoot bearing primordia with associated axillary primordia,some of the latter being precocious in their development. Silent weli-rosa, flower initiation, flower development, phyllotaxis, primordia     

Photoperiodism in the Glasshouse Carnation: The Effectiveness of Different Light Sources in Promoting Flower Initiation

Carnations (Dianthus) cultivar White Sim, were grown under photoperiodiccycles comprising 8 h of natural daylight followed by 16-h ‘nights’during which different lighting treatments were given. Irradiationwith tungsten-filament lamps throughout the night was the mosteffective treatment for the promotion of flower initiation.Irrespective of the timing or duration of the lighting, tungstenfilamentlamps were more effective than ‘daylight’ fluorescentlamps. Promotion of flower initiation due to radiation from a far-redsource was greatest when irradiation followed immediately afterthe period of natural daylight and was least when it immediatelypreceded the period of daylight. Promotion of flowering dueto a red source was least when the effect of far-red was greatest.Red and far-red radiations were synergistic in their promotionof flower initiation when given simultaneously for a periodof 4 h in the middle of the night. It is suggested that in thepromotion of flower initiation in long-day plants, a requirementfor a relatively long duration of irradiation is related physiologicallyto a requirement for a relatively high proportion of far-redradiant energy.     

Factors Affecting the Flowering of Andropogon gayanus Kunth. Responses to Photoperiod, Temperature and Growth Regulators

Andropogon gayanus is a short-day plant with a critical daylengthfor flowering between 12 and 14 h. Flowering is more intenseas the daylength is shortened from 12 h to 8 h, initiation isalso accelerated by increasing durations of short-day treatment.Plants flower more readily with increasing age. The maximumflowering response can be induced by short-day exposure of onlyone expanding leaf. A fixed number of short days distributedamong different groups of leaves on the plant gave less floweringthan the same number given to only one group. Approximately25°C was optimal for flowering. Root removal treatmentsin short day reduced both growth and flowering responses. Application of the growth regulators indol 3yl-acetic acid,abscisic acid, gibberellic acid or dimethylaminosuccinamic acid(B9) was inhibitory to flowering in all cases but gibberellicacid and B9 applied simultaneously had no inhibitory effect.Growth hormone treatments failed to stimulate flower developmentin long day. These results are discussed in relation to the internal mechanismscontrolling growth and flowering.     

Environmental Control of Flowering in Vicia faba L.

There is a heteroblastic change in leaflet number in many stocksof Vicia faba, the rate of change being affected by the temperatureand photoperiod under which the plants are grown. In all exceptthe earliest flowering stocks of broad beans, and particularlyat high temperatures, flower initiation shows a quantita-tivelong-day response. For full development of the initiated inflorescenceslong days are required. Flower initiation may be accelerated in all except the earliestflowering stocks of V.faba by brief exposures to low temperatures,particularly when the plants are grown in short days at hightemperatures. The response to low temperatures is more rapidat I0° C. than at 4° C. but eventually approaches saturationat both temperatures. More prolonged exposure to low temperaturesdelays flower initia-tion. The response to low temperaturesincreases with increasing plant age but can occur during embryodevelopment on the mother plant. At temperatures above 14° C, and particularly above 23°C, a reaction inhibitory to flower initiation occurs. This reactionis probably restricted to the diurnal dark periods but is operativeat all stages of the life cycle, including embryo development.Its inhibitory effects may be overcome by subsequent cold treatment,and when the low temperature processes have reached saturationsubsequent high temperatures are no longer inhibitory. Although nucleosides could accelerate flower initiation, purineand pyrimidene analogues did not, with one exception, reducethe response to low temperature treatment.     

The Mechanism of Action of Vernalization in Lathyrus odoratus L.

In the sweet pea (Lathyrus odoratus L.) genes Dn^l andDr^h controlthe production of a graft-transmissible substance which delaysflowering and promotes outgrowth of basal laterals. Seed vernalizationpromotes flowering and reduces lateral outgrowth in intact plantsand grafted scions of genotype DnⁱDn^l, suggesting that vernalizationreduces output of the Dnⁱ system, possibly by disrupting therelationship between chronological and plastochronic age. Whenlateral outgrowth and floral abortion are used as indicatorsof inhibitor levels, it can be shown that vernalized Dnⁱ plantspossess more inhibitor but initiate flower buds at a lower nodethan unvernalized dn plants. This supports the suggestion thatin regard to floral initiation vernalization also alters thesensitivity of the shoot apex to the flowering hormone(s). InLathyrus odoratus an hormonally based vernalization responseof considerable magnitude can be shown for day-neutral (dndn)lines, supporting the suggestion that vernalization also influencesthe level of a flower promotor. Lathyrus odoratus L., sweet pea, vernalization, flowering, branching, genotype, grafting     

Effects of Growth Retardants, Gibberellic Acid and Indol-3-ylacetic Acid on Stem Extension and Flower Development in the Pot Chrysanthemum (Chrysanthemum morifolium Ramat)

The growth retardants chlorphonium chloride, daminozide anda new, quaternary ammonium compound, piproctanyl bromide, allreduced shoot length and delayed the time of flowering of thepot chrysanthemum (Chrysanthemum morifolium Ramat) cv. BrightGolden Anne grown throughout in short days. The retardants delayedflowering by reducing the rate of flower bud development andnot by influencing bud initiation. In the case of chlorphoniumchloride and daminozide, a single dose of 20 or 40 µggibberellic acid (GA) completely overcame the effects on bothstem length and flowering, whereas when piproctanyl bromidehad been applied GA did not always bring about a total reversal.Responses to GA were recorded a few days after its application.Neither the retardants nor Ga altered leaf number. Only whenpiproctanyl bromide was the retardant did indol-3-ylacetic acidproduce a small but significant increase in stem length at flowering. The results are consistent with a theory of retardant actionin which gibberellins play the dominant role and strongly suggestthat these hormones are a major factor influencing both stemextension and the rate of flower-bud development in the chrysanthemum.They may promote flower development and thus hasten floweringby attracting assimilates to these organs. Chrysanthemum morifolium Ramat, stem extension, flower development, growth retardants, gibberellic acid, indol-3-ylacetic acid     

Effects of some metabolic inhibitors on flowering of Lemna gibba G3, a long-day duckweed

Flowering of Lemna gibba G₃, a long-day duckweed, was inhibitedby adding CuSO₄, AgNO₃, HgCl₂, Na₂WO₄ or iodoacetamide to themedium at the concentrations inducing long-day flowering inLemna paucicostata 6746, a short-day duckweed. This suggeststhat these metabolic inhibitors affected the photoperiodic sensitivityrather than directly affecting flower initiation. Ferricyanidepromoted flowering in both of these short-day and long-day duckweeds. (Received July 7, 1977; )     

A Modification of Flowering and Phyllotaxis in Silene

Modified proliferous flowers arose spontaneously in a smallproportion of plants of Silene coeli-rosa growing in gardenplots. The modified flowers consisted of leaves, arranged spirallywith a mean divergence angle of 138.4° instead of the pentamerousarrangement of the normal flower, and sometimes also carpelswhich ranged from open structures with exposed ovules to follicle-likestructures, free or fused, to fully fused carpels with free-centralplacentation. In the modified flowers petals and stamens werenot formed. The primordia at initiation were intermediate insize (relative to the apical dome) between normal leaf and normalsepal primordia but were the same absolute size as the latter.The structure of these anomalous flowers is discussed in relationto the normal flowering process. Silene coeli-rosa, flowering, phyllotaxis     

Observations on the Growth of Carnation (Dianthus caryophyllus L.) in Natural and Long Days

Observations were made on the growth and development of carnationsgrown in containers under natural or 24 h days. The number ofleaf pairs produced before flower initiation and the final lengthof each flowering stem were affected by the date at which theshoot appeared and its position on the plant. Dusk-to-dawn lighting reduced the number of axillary shootsin each generation but increased their rate of development.This resulted in similar numbers of flowers being produced inboth treatments. Dianthus caryophyllus L., Carnation, growth, flowering, day length     

Synchronization of Cell Division During Flower Initiation in Third-Order Buds of Silene

Plants of Silene coeli-rosa were induced to flower with sevenlong days and then returned to non-inductive short days. Third-orderbuds were formed more than three weeks after the beginning ofinduction and third-order flowers were initiated about one weeklater. Comparison of the mitotic index with the ratio of cellsin the G2 and G1 phases of the cell cycle for each third-orderapex provided evidence for synchronization of cell divisionjust before flower initiation. It is suggested that this resultsfrom changes of competence of the apical cells to react to theirinternal environment rather than because of the arrival of afloral stimulus at the shoot apex. Silene, cell division synchrony, flowering, evocation, mitotic index, cell cycle, competence     

Photoperiod Sensitivity during Flower Development of Opium Poppy (Papaver somniferum L.)

Photoperiod is a major factor in flower development of the opiumpoppy (Papaver somniferum L. ‘album DC’) which isa long-day plant. Predicting time to flower in field-grown opiumpoppy requires knowledge of which stages of growth are sensitiveto photoperiod and how the rate of flower development is influencedby photoperiod. The objective of this work was to determinewhen poppy plants first become sensitive to photoperiod andhow long photoperiod continues to influence the time to firstflower under consistent temperature conditions. Plants weregrown in artificially-lit growth chambers with either a 16-hphotoperiod (highly flower inductive) or a 9-h photoperiod (non-inductive).Plants were transferred at 1 to 3-d intervals from a 16- toa 9-h photoperiod andvice versa . All chambers were maintainedat a 12-h thermoperiod of 25/20 °C. Poppy plants becamesensitive to photoperiod 4 d after emergence and required aminimum of four inductive cycles (short dark periods) beforethe plant flowered. Additional inductive cycles, up to a maximumof nine, hastened flowering. After 13 inductive cycles, floweringtime was no longer influenced by photoperiod. These resultsindicate that the interval between emergence and first flowercan be divided into four phases: (1) a photoperiod-insensitivejuvenile phase (JP); (2) a photoperiod-sensitive inductive phase(PSP); (3) a photoperiod-sensitive post-inductive phase (PSPP);and (4) a photoperiod-insensitive post-inductive phase (PIPP).The minimum durations of these phases forPapaver somniferum‘album DC’ under the conditions of our experimentwere determined as 4 d, 4 d, 9 d, and 14 d, respectively. Anthesis; days to flowering; flower bud; opium poppy; Papaver somniferum L.; photoperiod; photoperiod sensitivity; predicting time to flowering; transfer