Significance of timing and number of short-day cycles for initiation and subsequent development of floral buds in Lemna perpusilla 6746

Time courses of the flowering process in Lemna perpusilla 6746,a short-day plant, were studied using selected fronds in relationto the order of emergence. Various numbers of short-day cycleswere interposed during continuous light. The floral buds evokedby short-day cycles developed to a floral stage determined bythe number of short-day cycles 3 days after the transfer toconsecutive long-day cycles, but aborted on the next day, regardlessof the floral stages. At least 2 long-day cycles were requiredfor the abortion of the floral buds at any stage of development.These results suggest the importance of the number of short-daycycles not only for initiation but also for development of floralbuds. (Received February 4, 1977; )     

Flowering response of Lemna perpusilla 6746 to a single dark period

Lemna perpusilla 6746 is induced to flower by a single longdark period, but the floral buds once formed disappear afterseveral days under 5000 lux/25?C. Such regression of floralbuds is prevented by lowering the light intensity or temperature,but if the light intensity and/or temperature are lowered beyondcritical levels, new floral buds form. If the cultures are subjectedto 100 lux/20?C, neither regression nor new formation of floralbuds occurs. Under such conditions, the number of floral frondsreaches maximum about 6 days after the inductive dark periodand reamins unchanged for at least 10 days, while the percentageof floral fronds rapidly decreases thereafter, owing to thedilution by newly developed vegetative fronds. When the cultures are subjected to various lengths of a singledark period (25?C) followed by 100 lux/20?C, flowering responsesrepresented by the number of floral fronds per flask show rhythmicfluctuation with a cycle length of about 24 hr. Similar rhythmicresponse is observed when a brief light interruption is givenat different times during a single long dark period. (Received December 2, 1974; )     

Chemical Factors Controlling Floral Bud Formation of Torenia Stem Segments Cultured in Vitro I. Effects of Mineral Nutrients and Sugars

Internodal segments of Torenia fournieri Lind. were culturedon various media to investigate chemical factors influencingin vitro flowering. The elimination or dilution of ammoniumnitrate from Murashige and Skoog's medium increased the formationof adventitious buds which subsequently differentiated floralbuds. The dilution of mineral salts in Murashige and Skoog'smedium enhanced adventitious bud formation, but did not influencethe ratio of cultures with floral buds to those with adventitiousbuds. Among various media tested, in vitro floral bud formationand development of Torenia was best on a medium having 1/5 ofthe mineral salts and no NH₄NO₃. Eighty-seven percent of thecultures produced floral buds on this medium. Using this medium,the effects of various sugars were also examined. Increasingthe concentration of sucrose in the medium (up to 60 g/liter)increased the rate of cultures with floral buds, and stimulatedthe development of floral buds led to anthesis. (Received January 17, 1981; Accepted February 21, 1981)     

Photoperiodic studies on growth and development of Impatiens balsamina L.

Summary In the short-day plant Impatiens balsamina it was found that, while floral buds are initiated with 3 short-day (SD) cycles, at least 8 such cycles are required for flowering. The numbers of floral buds and open flowers bear a linear relationship with the number of SD cycles. The induced floral buds revert to vegetative growth unless the plants receive the minimum number of SD cycles needed for flowering, this reversion occurring in a basipetal direction. The rate of extension growth of the stem increases with increasing numbers of SD cycles. The high rate is maintained longer in plants receiving 32 or more SD cycles, but the subsequent fall is also steeper in these plants than in plants receiving less inductive cycles. Senescence also occurs in these plants and appears to be related to the magnitude of reproductive development and the high rate of extension growth.     

Effects of gibberellic acid and some diphenols on the flowering of Impatiens balsamina L., a qualitative short day plant

Res, DOPA and CA resemble GA₃ in inducing floral buds in Impatiensbalsamina under strictly non-inductive photoperiods, while Catdoes not do so. 1 mg/liter Res and 100 mg/liter CA in combinationwith 100 mg/liter GA₃ even hastened the initiation of floralbuds. All the tested phenols, in combination with 100 mg/literGA₃, caused a synergistic increase in the number of floral buds. (Received November 24, 1977; )     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

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     

Floral initiation under continuous light in Pharbitis nil, a typical short-day plant

Seedling-cuttings of Pharbitis nil, a typical short-day plant,initiated floral buds under continuous light of 2200–2400lux at 24–26?C. When cultured under poor-nutritional conditions,the node bearing the first floral bud was as low as the 4thone. A close relation between floral initiation under continuouslight and retarded vegetative growth was observed. (Received September 28, 1973; )     

Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica

Aims Viola philippica is a species with a typical chasmogamous-cleistogamous (CH-CL) mixed breeding system. It provides a flower model system to investigate floral organs development under different photoperiods. Morphological changes of intermediate cleistogamous (inCL) flowers have been observed, the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed, the localized effects of poorly developed stamens and petals in CL and inCL flowers have been identified. This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development.Methods We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods.Important findings Photoperiod played an important role in the development of CH and CL flowers in V. philippica. Under short-day light and intermediate-day light, both CH and inCL flowers developed simultaneously. Most of the floral buds were CH flowers under a photoperiod of short-day light, but most of the floral buds were inCL flowers under mid-day light. Complete CL flowers formed under long-day lights. However, there were a series of transitional types in the number and morphology of stamens and petals among inCL flowers, including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers. The former type was dominant under short-day light conditions, and the latter type was dominant under mid-day light. Further more, there were localized effects in stamen and petal development for CL and inCL flowers. The development of ventral lower petal (corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in inCL flowers were best, and the back petal was similar to that of CL flowers, an organ primordium structure. The adjacent stamens with the back petals tended to be poorly developed. In extreme cases, these stamens in inCL flowers had no pollen sac, only a membranous appendage or even a primordium structure. When the plants with CL or CH flowers were placed under short-day light or long-day light, the newly induced flowers all showed a series of inCL flower types, finally the CL flowers transformed into CH flowers, and the CH flowers transformed into CL flowers. This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V. philippica. A long photoperiod could inhibit the development of partial stamens and petals, and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.     

Flower formation in vitro in a quantitative short-day tobacco: interrelation between photoperiod and infructescence development

The flowering response of thin layers excised from branch internodes of Nicotiana tabacum cv. Maryland Catterton (quantitative short-day plant for induction) was studied under three photoperiodic treatments. The explants were excised from inflorescences bearing flowers only, flowers and green fruits, or from infructescences with green fruits only. The aim of the study was to investigate the post-inductive photoperiodic effects on in vitro flower bud formation in a quantitative short-day tobacco and the relation with infructescence development. Short days quantitatively enhanced the flower bud regeneration capacities of explants in all stages of development, both as number of explants induced to produce flowers and as mean number of flowers per explant. There was no significant difference in flower bud formation on explants of the first two stages, which produced much more flowers than those of the third stage. Observations in planta showed that, during the 20 days separating the second stage from the first stage, there was no significant difference in the number of floral buds and flowers present on the inflorescence; however, the branch internodes lengthened, as did the floral buds and flowers. During the 10 days leading to the third stage, the number of capsules did not change significantly, but a high rate of floral abscission occurred. The present results show that in Nicotiana tabacum cv. Maryland Catterton short day quantitatively controls not only the inductive step of the flowering process, but also affects the capacity to regenerate flower buds during the late post-inductive phases. The responsiveness to the photoperiodic signal decreases only when the plant exhibits only fruits.     

Effects of IAA, Zeatin, Ammonium Nitrate and Sucrose on the Initiation and Development of Floral Buds in Torenia Stem Segments Cultured In Vitro

In Torenia stem segments cultured on a defined medium from whichammonium nitrate and growth regulators were omitted, adventitiousbuds were readily formed from epidermal tissue, with subsequentdifferentiation of floral buds. Using this plant material, thecorrelation between the time of application of various chemicalsand the time-course of floral bud differentiation was investigated.Histological examination showed that adventitious buds werevegetative during the first two weeks of the culture, and floralprimordia appeared after about three to four weeks of culture.We divided the flowering process in Torenia stem segments intothe following 3 phases: the first phase (first 2 weeks) duringwhich adventitious buds are formed, the second phase (3rd and4th weeks) during which floral buds are initiated and the thirdphase (5th to 12th weeks) during which floral buds develop.Then we added IAA, zeatin, ammonium nitrate or a high concentrationof sucrose to the medium during one, two or three of these phases.Ammonium nitrate added during the third phase suppressed floralbud development, but the high concentration of sucrose givenduring this phase stimulated it. These two chemicals influencedonly the development of floral buds previously initiated. Theapplication of IAA during the first phase promoted both theinitiation and development of floral buds. However, its applicationafter 2 weeks of culture failed to promote floral bud formation.Zeatin inhibited floral bud formation in a manner similar toammonium nitrate, but if it was added to the medium only duringthe first phase, it slightly promoted the initiation and developmentof floral buds. (Received July 7, 1981; Accepted October 12, 1981)     

Intergeneric Translocation of Floral Stimulus across a Graft in Monoecious Cucurbitaceae with Special Reference to the Sex Expression of Flowers

The effect of floral stimulus on flower sex expression in monoeciouscucurbits was examined using a qualitative short-day plant,Sicyos angulatus L. Sicyos was induced to flower not only bygrafting it onto a flower-induced plant of the same speciesbut also by intergeneric grafting Onto the day-neutral plantCucumis sativus L. or the quantitative short-day plant Luffacylindrica Roem under noninductive long-day conditions. Sicyosplant grafted onto various cucumber varieties having differentgenetic backgrounds for their sex expression developed bothstaminate and pistillate inflorescences with similar sex expression.When the availability of floral stimulus was restricted as inthe case of grafting of Sicyos onto young cucumber seedlingsat the cotyledonary stage, most inflorescences appearing onthe Sicyos were staminate ones. Pistillate flowers formed onthe cucumber receptors substantially increased when they weregrafted onto Sicyos donors which had a sufficient number ofleaves induced by short-days as compared with those graftedonto noninduced ones. These results suggest that the availabilityof floral stimulus participates in the sex expression of flowersin Cucurbitaceae. Undeveloped pistillate inflorescences, whichoccasionally appear on Sicyos scion, flowered normally whenN⁶-benzylaminopurine was directly applied to the inflorescence. (Received February 27, 1981; Accepted October 16, 1981)     

Floral initiation of Pharbitis nil, a short-day plant, under continuous high-intensity light

Pharbitis nil, a short-day plant, initiated floral buds undercontinuous illumination at 23°C, provided that the lightintensity was kept at 16,000 lux or above. Stem elongation ofthe plants was strongly inhibited but leaves developed normallyunder this condition. (Received November 26, 1971; )     

Floral induction by gibberellic acid in Impatiens balsamina,a qualitative short-day plant

Summary In the qualitative short-day plant Impatiens balsamina, gibberellic acid (GA₃) not only promoted the formation of floral buds in response to suboptimal photoinductive conditions and reduced the number of SD cycles that are required for their development into flowers, but also caused initiation of floral buds under non-inductive photoperiods. In plants treated with repeated applications of GA₃, the floral buds developed into flowers irrespective of whether the apex was left intact or was removed. In those that received a single application of GA₃ the floral buds developed into flowers only in decapitated plants.     

Floral bud reversion in Impatiens balsamina under non-inductive photoperiods

Summary All floral buds of Impatiens balsamina plants exposed to 4 short-day (SD) cycles and then returned to long days reverted to vegetative growth. The same happened with the upper buds of plants receiving a larger number of SDs, even as many as 90 cycles. The reversal proceeded in a basipetal order. The number of floral buds and flowers increased, and their reversion to vegetative growth was delayed with increasing numbers of SD cycles. Depending upon the stage attained by the floral bud before the transfer of the plant to noninductive photoperiods one or more inner whorls of the flower were replaced by a vegetative apex. The tip of the placenta was able to resume vegetative growth even after the formation of fertile anthers and an ovary with abortive ovules, showing that the potentiality for reversion is maintained till quite late stages in floral bud development. Continuous exposure to SD cycles is required not only for the continued production of floral buds, but also for their development to mature flowers, indicating that the floral stimulus in this plant is not self-perpetuating.     

Effect of decapitation, phosfon D and cycocel on the flowering of Impatiens balsamina exposed to varying numbers of short days

Impatiens balsamina L., a qualitative short day plant, requiresmore short days for the development of floral buds into flowersthan for their initiation. Phosfon D and cycocel reduce thenumber of short days required for flowering, increase the numberof floral buds and flowers and delay their reversion to vegetativegrowth when transferred to noninductive conditions. The effectof decapitation of the main shoot subsequent to the emergenceof floral buds resembles that of retardants indicating thatthe effect of the latter in flower promotion in this plant maybe by virtue of their effect on cessation of apical dominanceas a consequence of which reserve food materials may be channeledto axillary floral buds enabling them to develop into flowers. (Received January 9, 1969; )     

Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica北大核心CSCD

Aims: Viola philippica is a species with a typical chasmogamous-cleistogamous (CH-CL) mixed breeding system. It provides a flower model system to investigate floral organs development under different photoperiods. Morphological changes of intermediate cleistogamous (inCL) flowers have been observed, the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed, the localized effects of poorly developed stamens and petals in CL and inCL flowers have been identified. This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development. Methods: We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods. Important findings: Photoperiod played an important role in the development of CH and CL flowers in V. philippica. Under short-day light and intermediate-day light, both CH and inCL flowers developed simultaneously. Most of the floral buds were CH flowers under a photoperiod of short-day light, but most of the floral buds were inCL flowers under mid-day light. Complete CL flowers formed under long-day lights. However, there were a series of transitional types in the number and morphology of stamens and petals among inCL flowers, including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers. The former type was dominant under short-day light conditions, and the latter type was dominant under mid-day light. Further more, there were localized effects in stamen and petal development for CL and inCL flowers. The development of ventral lower petal (corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in inCL flowers were best, and the back petal was similar to that of CL flowers, an organ primordium structure. The adjacent stamens with the back petals tended to be poorly developed. In extreme cases, these stamens in inCL flowers had no pollen sac, only a membranous appendage or even a primordium structure. When the plants with CL or CH flowers were placed under short-day light or long-day light, the newly induced flowers all showed a series of inCL flower types, finally the CL flowers transformed into CH flowers, and the CH flowers transformed into CL flowers. This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V. philippica. A long photoperiod could inhibit the development of partial stamens and petals, and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.     

Effects of Number of Photoperiodic Cycles on Induction and Development of Flowers and Fruits in Corchorus olitorius L. (var. oniyaya Epen.)

Plants of Corchorus olitorius, a short-day plant, were subjectedto varying numbers of short-day cycles before transfer to longdays. Treatments started after germination of the seeds at thetime of cotyledon release. Four short-day cycles (10 h naturaldaylight followed by 14 h darkness) were sufficient to induceflowering in all plants. The number of flowers and fruits producedon a plant increased as the number of short-day cycles was increasedfrom three to 30. Plants given three to seven short-day cyclesproduced flowers on the main stem only but when plants weremaintained in short days for longer periods, flowers were alsoproduced on the branches. The growth in d. wt of fruits wasgreatest when plants were maintained in short days throughout. Corchorus olitorius L., flowering, fruit development, photoperiodism     

COMPARATIVE FLOWER DEVELOPMENT IN THE CLEISTOGAMOUS SPECIES VIOLA ODORATA. I. A GROWTH RATE STUDY

In Viola odorata, chasmogamous (CH) or open flowers and small, short-petioled leaves are produced under 11 hr or less of daylight, cleistogamous (CL) or closed flowers and large, long-petioled leaves under 14 hr or more of daylight, and intermediate floral and leaf forms under transitional photoperiods. CL flowers are approximately four times smaller than CH flowers and differ morphologically in repressed growth of the anterior petal spur and staminal nectaries, and recurving of the style which remains enclosed within the cone formed by anther appendages. Both CH and CL shoot systems conform to a (2 + 3) phyllotaxis with minor differences in leaf divergence angles and phyllotactic indices. The larger CL leaf grows significantly faster than the CH leaf, and an increased rate of leaf initiation occurs in the CL apex represented by a plastochron of 3.4 days compared to 4.3 days in the CH apex. The plastochron index was used to indirectly age young floral primordia nondestructively until prophase of meiosis I within the anthers. This event occurs 8 days earlier in the CL than the CH flower. Time from meiosis until flower maturity, determined by direct observation, is about 14 days for the CL flower, versus 21 days for the CH flower.     

Naturally occurring variation in high temperature induced floral bud abortion across Arabidopsis thaliana accessions

A system to study the basis of high temperature-induced floral bud abortion using naturally occurring variation for heat-tolerance of floral development among Arabidopsis thaliana (L.) Heynh. wild-collected accessions is described. High temperature-induced floral bud abortion was dependent on both temperature and duration of exposure. Normalizing high temperature exposures to degree-hours (°C-h) above 33 °C indicated that abortion of flower buds increased as exposure increased between 200 and 300 °C-h above 33 °C and exposures > 300 °C-h above 33 °C resulted in abortion of the entire primary inflorescence. Thirteen wild-collected Arabidopsis accessions representing a latitudinal gradient were screened for variation in high temperature-induced floral bud abortion, and Col-0 and No-0 were selected as models for heat-tolerance and -sensitivity for flower development, respectively. No-0 flower buds were heat-sensitive across a wider range of developmental stages (stages 9–12, compared to stage 12 for Col-0 flower buds). Exposing the inflorescence alone to high temperature was sufficient to induce floral bud abortion, and Col-0 and No-0 photosynthetic rates were similar during high temperature exposure and recovery, indicating that high temperature induced floral abortion is not simply due to reductions in carbon assimilation under high temperatures. Determining that exposing floral buds alone to high temperature is sufficient to induce abortion and identifying the stages of floral development sensitive to high temperature-induced abortion will aid in identifying the developmental events subject to disruption under high temperatures.