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; )     

The Effect of Cotyledon Excision on Reproductive Development in Pea (Pisum sativum L.)

The excision of cotyledons from two cultivars of peas soon aftergermination resulted in a lowering of the node of first floweringas well as a delay in both flower initiation and flowering,especially in the late cultivar Greenfeast. This is contraryto the usual view that, when cotyledon excision reduces nodeof first flowering, flower initiation and flowering are hastened,and it seems irreconcilable with the colysanthin theory of Barber(1959). An alternative explanation is proposed.     

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     

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     

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     

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     

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     

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     

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.     

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.     

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     

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     

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.     

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; )     

Rates of Growth and Primordial Initiation During Flower Development in Silene at Different Temperatures

The growth of the flower and its constituent parts was measuredin Silene coeli-rosa plants, induced at 13, 20 and 27 °C,in order to try and identify those processes which consistentlyoccurred and would therefore be more likely to be essentialfor flower formation. The increased growth rate of the apical dome just before orabout the time of sepal initiation was not maintained in theflower, the growth rate of which was comparable to that of avegetative apex until all the carpels had been initiated, whenit decreased further. The primordia of the same whorl all hadsimilar growth rates so that the relative sizes of the primordiareflected their relative ages since their initiation. The relativegrowth rate of the stamens was the same (13 and 20 °C) orless (27 °C) than that of the sepals, but the relative growthrate of the petals was lower than either. The growth rate ofthe flower axis was least at the sepal node and increased bothdistally and proximally from this region. The plastochron during sepal initiation was shorter than forleaf initiation and tended to be shorter still during initiationof stamens and petals. Increasing temperature increased therate of primordial initiation but at 27 °C the growth ratesof the primordia were lowest although the rates of primordiainitiation were highest. The form of the flower, as exemplifiedby the relative sizes of the primordia at the moment when allcarpels had been initiated, was constant despite the differinggrowth rates and sizes of the primordia on initiation in differenttemperatures. It is concluded that neither the initiation ofthe primordia in the flower nor the form of the flower is determinedprimarily by the relative growth rates of its component parts. Silene coeli-rosa, flower development, primordia initiation, growth     

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     

Distribution of Cashew Flower Sex-types between Clones and Sides of Tree Canopies in Tanzania

Production of male, hermaphrodite and abnormal flowers was studiedon the north, east, south and west sides of the cashew treecanopy from Jul. to Dec. 1992 at the Agricultural Research InstituteNaliendele, Southern Tanzania. Flowers were recorded daily onselected clones throughout the main flowering season and subsequentlyyield of each clone was also recorded. Results showed differencesin the number of flower types both between clones and betweensides; however, there were consistently more male than othertypes of flower. Significant yield differences between cloneswere not detected and so could not be used to provide unambiguousevidence of the relationship between yield and flower characteristicsbut did indicate that clonal differences were present in termsof earliness of yield production. Anacardium occidentale L.; cashew; flowering; sex-types; clones; Tanzania; sides of canopy; yield     

Node of Flowering as an Index of Plant Development

The interrelation between node of flowering, rate of node productionand times of flower initiation, and flowering is examined andthe limitations of node of flowering as an index of developmentdefined. Node of flowering is shown to be useful as an indexof development only in so far as it can be used to estimatetime of flower initiation and for this to be possible, informationon rate of node production is also required.     

Nitrogen Deficiency Slows Leaf Development and Delays Flowering in Narrow-leafed Lupin

Effects of nitrogen (N) supply on leaf and flower developmentinLupinus angustifolius L. cv Merrit were examined in a temperature-controlledglasshouse. Low N supply (0.05 or 0.4 mM N) had little effecton leaf initiation but slowed leaf emergence on the main stemcompared with plants receiving high N supply (6.0 or 6.4 mMN), or with symbiotic N₂-fixation. Plants experiencing transientN deficiency had slower leaf emergence than plants with a continuoussupply of 6.4 mM N. Nitrogen supply did not affect the timeof floral initiation, which occurred within 4 weeks of sowing,by which time nine to ten leaves had emerged. However, the floweringof low-N plants was delayed by 68 to 220 °C d (i.e. 4–14d) even though they had fewer leaves. The effect of N deficiencyon flowering time was largely a result of slower leaf emergence. Lupinus angustifolius L.; nitrogen; leaf; flower initiation; thermal time; plastochron; phyllochron