Effects of Kinetin on Growth of the Apical Meristem and Floral Differentiation in Chenopodium rubrum L.

Kinetin (1•10^–4 M and 1•10^–3 M) was appliedto the plumules of 6-day-old Chenopodium rubrum plants. Effectson growth, anatomical structure and organogenesis in the apicalmeristem were followed. Floral differentiation as affected bykinetin was also investigated in plants induced to flower byshort-day treatment. Kinetin increased mitotic activity in the apical meristems inboth induced and non-induced plants. The effect was most pronouncedin the peripheral and subcentral zone. An increase in nucleolussize and a higher degree of pyroninophilia in the peripheralzone was also observed, indicating a localized promotion ofRNA synthesis. A higher rate of leaf initiation and a stimulationof leaf and stem growth was subse quentiy recorded. The growthof axillary meristems and of bud primordia was promoted onlyat the lower concentration of kinetin (1•^10–4 M),in both photoperiodically-induced and non-induced plants. However,the pattern of lateral bud growth differed from that found innormal floral differentiation. In kinetintreated plants, thebud primordia are isolated from the summit of the shoot apexby a succession of rapidly growing leaves. The enhancement ofleaf growth leads to correlative inhibition of axillary budpriniordia and results, finally, in a suppression of floraldifferentiation. The inhibitory effect of kinetin on floweringwas compared with that of auxin. Inhibition of flowering occurredin both cases but is achieved in two different ways.     

Bi-directional inflorescence development inArabidopsis thaliana: Acropetal initiation of flowers and basipetal initiation of paraclades

In this study we investigated Arabidopsis thaliana (L.) Heynh. inflorescence development by characterizing morphological changes at the shoot apex during the transition to flowering. Sixteen-hour photoperiods were used to synchronously induce flowering in vegetative plants grown for 30 d in non-inductive 8-h photoperiods. During the first inductive cycle, the shoot apical meristem ceased producing leaf primordia and began to produce flower primordia. The differentiation of paraclades (axillary flowering shoots), however, did not occur until after the initiation of multiple flower primordia from the shoot apical meristem. Paraclades were produced by the basipetal activation of buds from the axils of leaf primordia which had been initiated prior to photoperiodic induction. Concurrent with the activation of paraclades was the partial suppression of paraclade-associated leaf primordia, which became bract leaves. The suppression of bract-leaf primordia and the abrupt initiation of flower primordia during the first inductive photoperiod is indicative of a single phase change during the transition to flowering in photoperiodically induced Arabidopsis. Morphogenetic changes characteristic of the transition to flowering in plants grown continuously in 16-h photoperiods were qualitatively equivalent to the changes observed in plants which were photoperiodically induced after 30 d. These results suggest that Arabidopsis has only two phases of development, a vegetative phase and a reproductive phase; and that the production of flower primordia, the differentiation of paraclades from the axils of pre-existing leaf primordia and the elongation of internodes all occur during the reproductive phase.     

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     

Development and Growth Potential of Axillary Buds in Roses as Affected by Bud Age

The effect of axillary bud age on the development and potentialfor growth of the bud into a shoot was studied in roses. Ageof the buds occupying a similar position on the plant variedfrom 'subtending leaf just unfolded' up to 1 year later. Withincreasing age of the axillary bud its dry mass, dry-matterpercentage and number of leaves, including leaf primordia, increased.The apical meristem of the axillary bud remained vegetativeas long as subjected to apical dominance, even for 1 year. The potential for growth of buds was studied either by pruningthe parent shoot above the bud, by grafting the bud or by culturingthe bud in vitro. When the correlative inhibition (i.e. dominationof the apical region over the axillary buds) was released, additionalleaves and eventually a flower formed. The number of additionalleaves decreased with increasing bud age and became more orless constant for axillary buds of shoots beyond the harvestablestage, while the total number of leaves preceding the flowerincreased. An increase in bud age was reflected in a greaternumber of scales, including transitional leaves, and in a greaternumber of non-elongated internodes of the subsequent shoot.Time until bud break slightly decreased with increasing budage; it was long, relatively, for 1 year old buds, when theysprouted attached to the parent shoot. Shoot length, mass andleaf area were not clearly affected by the age of the bud thatdeveloped into the shoot. With increasing bud age the numberof pith cells in the subsequent shoot increased, indicatinga greater potential diameter of the shoot. However, final diameterwas dependent on the assimilate supply after bud break. Axillarybuds obviously need a certain developmental stage to be ableto break. When released from correlative inhibition at an earlierstage, increased leaf initiation occurs before bud break.Copyright1994, 1999 Academic Press Age, axillary bud, cell number, cell size, pith, shoot growth, Rosa hybrida, rose     

Effect of Light Quality (Red:Far-red Ratio) at the Apical Bud of the Main Stolon on Morphogenesis of Trifolium repens L.

A controlled environment experiment investigated whether thered:far-red (R:FR) ratio of light at the apical bud of the mainstolon could alter plant morphogenesis in clonal cuttings ofwhite clover (Trifolium repens L.) The apical bud included theapical meristem, five to six developing leaf primordia withassociated axillary bud primordia and stipules and the firstemerged folded leaf until development was greater than 0·3on the Carlson scale. Three light regimes were imposed on theapical bud by collimating light from R or FR light-emittingdiodes so that the R:FR ratio of light incident at the apicalbud was set at 0·25, 1·6 or 2·1, withoutsignificantly altering photosynthetically active radiation.The effect of these light regimes on white clover seedling growthwas also tested. At a low R:FR ratio seedling hypocotyl and cotyledon lengthswere significantly longer. However, with the cuttings, the lighttreatments did not alter node appearance rate or internode lengthof the main stolon, petiole length, area of leaves or totalshoot dry matter. There was one significant photomorphogeneticresponse in the cuttings, a delay of 0·5 of a phyllochronin the appearance of branches from axillary buds in the lowR:FR ratio treatment relative to the other treatments. Wherebranch appearance was delayed plants had fewer branches. Thisdifference could be ascribed solely to a delay in branch appearanceas there were no significant treatment effects on either theinitiation of axillary bud primordia within the apical bud,the probability of branching or on the rate of growth of branchesafter appearance. Because treatment of the apical bud inducedonly one of the many previously observed responses of whiteclover to a decrease in the R:FR ratio of light, we concludethat other plant organs must also sense the quality of incidentlight.Copyright 1994, 1999 Academic Press White clover, Trifolium repens, apical bud, light quality, red:far-red ratio, light-emitting diode, branching, axillary buds, photomorphogenesis     

Cytophotometric Study of the 2C Nuclear DNA Content in the Apical Bud of Sinapis alba during Floral Transition

Feulgen cytophotometry was used to detect possible changes inthe 2C DNA content in the various parts of the apical bud ofSinapis alba during floral evocation and flower development.This study showed that there was no significant difference inthe 2C DNA content between the vegetative, evoked or reproductivemeristems. In vegetative plants, the 2C DNA content was lowerin the leaf primordia than in the meristem. This content inthe leaf exhibited a further decrease during the floral transition.In the flower primordia, the 2C value never exceeded the typicalvalue of the meristem. In the flower at anthesis, the DNA contentwas lower in the pistil and stamen than in the meristem. Apical bud, floral transition, 2C DNA content, cytophotometry, Sinapis alba L.     

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     

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     

Growth changes in the shoot apex of Sinapis alba during transition to flowering

The aim of the work was to report morphological changes whichoccur in the shoot apex during the morphogenetic switch to floweringin the model long day (LD) plant, Sinapis alba. During the floraltransition induced by 1 LD the growth rate of all componentsof the shoot apex is modified profoundly. The earliest changes,detected at 24 h after start of LD, include a decrease in plastochronduration and an increase of growth of leaf primordia. One daylater, the meristem dome starts to increase in volume, apicalinternodes have an increased height and there is a precociousoutgrowth of axillary meristems. All these changes precede initiationof flower primordia, which starts at about 60 h after the startof LD. Later changes include meristem doming, a decrease inthe plastochron ratio and a shift to a more complex phyllotaxis.All the changes, except the decreased plastochron ratio, arecharacteristics of an apex with an increased tempo of growth.The stimulation of longitudinal growth (height of apical intemodes)is more marked and occurs earlier than the reduction of radialgrowth (plastochron ratio). Key words: Axillary meristem, internode growth, leaf growth, plastochron ratio, plastochron duration     

The Initiation and Growth of Axillary Bud Primordia in Relation to Flowering in Trifolium repens L.

The initiation and growth of axillary bud primordia in relationto the growth of their subtending leaves was observed at theapices of three clones (A. B. and C) of white clover grown invarious combinations of photoperiod and temperature. ClonesA, B, and C flower in response to low temperatures, and clonesA and C, but not B, in response to a transfer from short tolong photoperiods at higher temperatures. The rate of growth of buds and leaves from node to node waslittle influenced by the various treatments imposed, but theinitiation of axillary bud primordia relative to the apicaldome was stimulated in conditions conducive to flowering. The number of budless leaf primordia at the apex ranged froma maximum average of 2.25 at 20° C. to approximately o.8oat 10° C. in all three clones. At the higher temperatures,runners possessed 2.06 budless nodes in short days but only1.12 in long days in clones A and C. In clone B, daylength didnot influence bud initiation at the higher temperature. The results provide evidence of the homology between vegetativeand repro-ductive axillary bud primordia. It is suggested thatflowering is brought about by the removal of an inhibition withinthe apex which leads to the precocious initiation of axillarybud primordia. Following the initiation of axillary bud primordia, the resultsshow their growth to be uninhibited for 6-7 plastochrons. Rapidinflorescence development occurs during this phase. Apical dominancehas no apparent influence on vegetative axillary buds untilthe onset of rapid petiole elongation in their subtending leaves.     

Axillary bud flowering after apical decapitation in Pharbitis in relation to photoinduction

The flowering response of axillary buds of seedlings of Pharbitis nil Choisy, cv. Violet, was examined in relation to the timing of apical bud removal (plumule including the first leaf or second leaf) before or after a flower-inductive 16-h dark period. When the apical bud was removed well before the dark period, flower buds formed on the axillary shoots that subsequently developed, but when removed just before, or after, the dark period, different results were observed depending on the timing of the apical bud removal and plant age. In the case of 8-day-old seedlings, fewer flower buds formed on the axillary shoots developing from the cotyledonary node when plumules were removed 20 to 0 h before the dark period. When the apical bud was removed after the dark period, no flower buds formed. Using 14-day-old seedlings a similar reduction of flowering response was observed on the axillary shoots developing from the first leaf node when the apical bud was removed just after the dark period. To further elucidate the relationship between apical dominance and flowering, kinetin or IAA was applied to axillary buds or the cut site where the apical bud was located. Both chemicals influenced flowering, probably by modulating apical dominance which normally forces axillary buds to be dormant.     

The Effects of Photoperiod on Flower-bud Development in Phaseolus vulgaris

For a variety of Phaseolus vulgaris of Peruvian origin, extendingthe daylength from 11 to 15 or 16 h with low-intensity incandescentor natural light, while not affecting the rate of initiationof flower primordia, inhibited the development of the flowerbuds and caused many, and sometimes all of them, to senesceand abscise. The inhibition of the oldest flower bud was firstdetected at the stage of pollen formation. The long photoperiodsalso inhibited the elongation and over-all development of theterminal inflorescence but, in contrast, promoted the elongationof those internodes below the first trifoliate leaf and alsothe elongation of the petioles.     

Changes in Apical Growth and Phyllotaxis on Flowering and Reversion in Impatiens balsamina L.

When plants of Impatiens balsamina L were subjected to 5 shortdays and then re-placed in long days, they began to form a terminalflower and then reverted to vegetative growth at this terminalshoot apex The onset of flowering was accompanied by an increasein the rate of initiation of primordia, an increase in the growthrate of the apex, a change in primordium arrangement from spiralto whorled or pseudo-whorled, a lack of internodes, and a reductionm the size at initiation of the primordia and also of the stemfrusta which give rise to nodal and internodal tissues On reversion,parts intermediate between petals and leaves were formed, followedby leaves, although in reverted apices the size at initiationand the arrangement of primordia remained the same as in thefloweing apex The apical growth rate and the rate of primordiuminitiation were less in the reverted apices than in floral apicesbut remained higher than in the original vegetative apex Sincethe changes in apical growth which occur on the transition toflowering are not reversed on reversion, the development oforgans as leaves or petals is not directly related to the growthrate of the apex, or the arrangement, rate of initiation orsize at initiation of primordia Impatiens balsamina L, flower reversion, evocation, phyllotaxis, shoot meristem     

NODE COUNTING IN AXILLARY BUDS OF NICOTIANA TABACUM CV. WISCONSIN 38, A DAY-NEUTRAL PLANT

A mature, quiescent, primary axillary bud on the main axis of a flowering Nicotiana tabacum cv. Wisconsin 38 plant, when released from apical dominance and before forming its terminal flower, produced a number of nodes which was dependent upon its position on the main axis. Each bud produced about one more node than the next bud above it. The total number of nodes produced by an axillary bud was about 6 to 8 greater than the number of nodes present above this bud on the main axis. At anthesis of the terminal flower on the main axis, mature, quiescent, primary axillary buds had initiated 7 to 9 leaf primordia while secondary axillary buds, sometimes present in addition to the primary ones, had initiated 4 to 5 leaf primordia. When permitted to grow out independently, primary and secondary axillary buds located at the same node on the main axis produced the same number of nodes before forming their terminal flowers. In contrast, immature primary axillary buds which had produced only 5 leaf primordia and which were released from apical dominance prior to the formation of flowers on the main axis produced only as many nodes as would be produced above them on the main axis by the terminal meristem, i.e., “extra” nodes were not produced. Therefore, it is the physiological status of the plant and not the number of nodes on the bud at the time of release from apical dominance that influenced the node-counting process of a bud. When two axillary buds were permitted to develop on the same main axis, each produced the same number of nodes as single axillary buds developing at these nodes. Thus, the counting process in an axillary bud of tobacco is independent of other buds. Axillary buds on main axes of plants that had been placed horizontally produced the same number of nodes as identically-positioned axillary buds on vertical plants, indicating that gravity does not play a major role in the counting, by an axillary bud, of the nodes on the main axis.     

Shoot Axillary Bud Morphogenesis in Kiwifruit (Actinidia deliciosa)

The annual cycle of kiwifruit [Actinidia deliciosa(A. Chev.)C. F. Liang et A. R. Ferguson var.deliciosacv. Hayward] shootaxillary bud (first-order axillary bud, FOAB) morphogenesisis described. FOABs developed quickly with the majority of budscales and leaf primordia present approx. 125 d after budbreak(dab). Mature FOABs had, on average, 23.2 bud scales and leafprimordia. Most second-order axillary structures were also presentapprox. 125 dab. During the growing season, the second-orderstructures developed into second-order axillary buds (SOABs)or remained as simple, dome-shaped meristems (SDSMs). At maturity,nearly all FOABs had four SOABs and, on average, 12.4 SDSMs.Most SDSMs were fused to the subtending leaf primordia, butsome SDSMs developed so that they were ‘free’ fromthe subtending leaf primordia. Third-order axillary meristems(third-order SDSMs) were observed in the axils of most SOABs,and, on average, there were 20.6 per FOAB. Our observationson the development of second-order axillary structures are consistentwith evocation in kiwifruit occurring earlier than the generally-acceptedtime of late summer. Actinidia deliciosa; bud morphogenesis; development; flowering; evocation     

Effect of Severity of Defoliation on the Viability of Reproductive and Vegetative Axillary Buds of Trifolium repens L.

This glasshouse experiment was performed to assess the effectsof a range of constant defoliation regimes applied to cuttingsof a single large-leaved genotype ofTrifolium repens L. on theviability of its axillary buds. Plants were established to comprisea single main stolon (axillary branches were removed) and defoliationtreatments were applied by removing the older (basal) leavesuntil leaf complements of 1·0, 1·5, 2·0,2·5, 3·0 or all leaves (control) remained. Basalleaves were subsequently removed as necessary to maintain thetarget leaf complements. Only severe defoliation (leaf complements of 1·0 and1·5) induced a loss of viability in axillary buds. Lossof viability was greatest in reproductive buds present withinthe apical bud when the treatments were first imposed. Althoughthe most severe treatment (leaf complement 1·0) resultedin death of half the plants, in plants surviving that treatment,death of vegetative axillary buds was restricted to 21% of thevegetative buds at the three youngest node positions withinthe apical bud at the time of treatment application. No othertreatment induced any loss of viability of vegetative buds.There was no loss of viability of axillary buds at nodes formedafter the treatments were imposed. The frequency of initiationof inflorescences at nodes formed after treatments were imposeddecreased as defoliation severity increased. Severe defoliation resulted in marked changes in plant morphologyindicative of a sharp decrease in availability of intraplantresources. It was concluded that under severe defoliation: (1)the potential for vegetative growth (as represented by viablevegetative axillary buds) was maintained at the expense of reproductivegrowth; and (2) that the loss of viability of axillary budswas associated with the sudden changes in physiological processesinduced by defoliation as there was no loss of viability inbuds formed after plants had adjusted their phenotype to oneof smaller size. Trifolium repens L.; white clover; defoliation; axillary buds; viability; inflorescences     

Topophysis affects the Potential of Axillary Bud Growth, Fresh Biomass Accumulation and Specific Fresh Weight in Single-stem Roses (Rosa hybrida L.)

Topophysis, the effect on growth and differentiation of positionof axillary buds along the shoot, was studied by propagatingfive-leaflet-leaf single-node cuttings which were excised fromseven stem positions and grown as single stemmed plants. InRosahybrida ‘Korokis’ Kiss®, ‘Tanettahn’Manhattan Blue®, and ‘Sweet Promise’ Sonia®,following release of the buds from apical dominance by excision,morphogenetic development was studied until anthesis. The timefrom excision/planting until onset of bud growth, visible flowerbud appearance, and anthesis was generally shorter in plantsoriginating from apical bud positions than from basipetal positions.Topophysis mainly affected the onset of axillary bud growth;the earliest growth and development was found in cuttings fromthe second uppermost node position. This node tended to havethe lowest plastochron value, which indicated the existenceof a transition between sylleptic and proleptic buds. Stem lengthat visible flower bud and at anthesis generally increased asthe cutting position changed basipetally until the second lowestposition, and the number of five-leaflet-leaves at anthesisand the total number of nodes generally increased basipetally.For internode length, growth rate, and fresh biomass efficiencythe cuttings taken from the uppermost and lowermost positionsgenerally had significantly lower values than cuttings fromall medial positions. At anthesis, plants originating from cuttingsexcised from lower medial positions generally had a higher freshweight, greater flower stem diameter, and a significantly higherspecific fresh weight than those plants originating from apicalor basal positions. Among the cultivars, Sonia was the mostefficient in increasing fresh biomass and had the highest growthrate, whereas Manhattan Blue possessed the highest specificfresh weight, indicating a higher plant quality. It is suggestedthat topophysis inRosa is an independent phenomenon intrinsicto the axillary bud. apical dominance; axillary bud growth; fresh biomass accumulation; cut rose; flowering; Rosaceae; Rosa hybrida L.; rose; shoot growth; single-stem roses; specific fresh weight; topophysis; quality     

Cell Cycle Patterns in the Shoot Apex of Lolium temulentum L. cv. Ceres During the Transition to Flowering Following a Single Long Day

Six-week-old Lolium temulentum cv. Ceres plants were inducedto flower by a single long day (day 1). The ‘double ridge’stage was reached on days 4/5. A detailed analysis of apicesevery 4 h on days 3 to 5 demonstrated synchronized cell divisionin the apex. However, this synchronized cell division occurredonly in the apical summit and axillary bud sites, i.e. onlyin those regions of the apex which give rise to the spikelets.This indicates a specific activation of the cells in these regions,rather than a general activation of the whole apex. Key words: Cell cycle, flowering, Lolium, shoot apex, spikelet     

Effects of Indol-3yl acetic Acid on Floral Induction and Apical Differentiation in Chenopodium rubrum L.

Indol-3yl acetic acid (10^–4M) was applied to the plumulesof Chenopodium rubrum. Effects on the anatomical structure andthe growth pattern in the apical meristem, as well as DNA synthesisand nucleolus size were investigated. When auxin is applied before or during photoperiodic inductionit inhibits DNA synthesis and meristematic activity. The axillarymeristem (i.e. a group of cells in the axils of the leaf primordia)is most affected. A similar inhibition of the axillary meristemwas also observed in non-induced control plants grown in continuouslight. Auxin applied simultaneously with photoperiodic inductioncounteracts the reduction of apical dominance in the apex andthus inhibits the onset of floral differentiation. Auxin appliedfollowing induction inhibits the previously-formed buds andmakes possible a more complete development of the apical flower. The dual effect of IAA on flowering, inhibitory and stimulatory,manifests itself as a growth response at different stages ofthe changing shoot apex.     

Phyllotaxis and the Initiation of Primordia During Flower Development in Silene

The measured divergence angles between successive primordiain the developing flower were compared with angles expectedon several hypotheses concerning primordial initiation. Theresults lead to the conclusion that the position and sequenceof initiation of the younger sepals is determined by the olderones but that the influence of an older primordium lasts foronly two plastochrons. The petals and carpels are apparentlypositioned by the sepals. The positions of the stamens are consistentwith their king determined by the sepals (antesepalous stamens)or petals (antepctalous stamens), but their sequence of initiationis consistent with its being determined, like the sepals, bythe two youngest primordia. The data indicate that there aretwo sets of factors governing the initiation of the primordiasubsequent to the sepals: one governing the positioning of theprimordia and resembling the factors governing the positionsof axillary buds, and the other governing the sequence of primordiaand resembling the factors which determine the initiation ofleaves. Measurements of the plastochron ratios were used tocalculate the sizes of the sepal, petal and stamen primordiaat initiation. At the moment of initiation the sepal primordiawere about one third, and the petal and stamen primordia aboutone sixth, of the size of the leaf primordia. In its early developmentthe Silene flower therefore resembles a condensed leafy shootwith precocious axillary buds but with primordia which are smallcompared to leaf primordia. Silene coeli-rosa, flower development, primordia, phyllotaxis