Induction of flowering ofImpatiens balsamina treated with gibberellic acid and resorcinol

Under strictly non-inductive photoperiods (24-h photoperiods) floral buds were initiated on plants receiving 25 treatments with Reso (resorcinol) or 8 treatments with GA₃ (gibberellic acid) or GA₃ + Reso, while water treated control plants did not flower at all. Although a single treatment of plants with GA₃ or GA₃ + Reso is not adequate to cause induction under LD conditions, its effect is added to the sub-threshold induction caused by one SD (short day: 8-h photoperiod) cycle. The initiation of floral buds was hastened with an increasing number of SD cycles accompanying respective number of treatments, the effect of GA₃ alone or together with Reso being more pronounced than that of Reso alone. GA₃ increased the number of floral buds more than Reso, the number being the highest in plants receiving the respective number of treatments with the combination GA₃ + Reso under both inductive as well as non-inductive photoperiods. Deceased.     

Effect of Gibberellic Acid, 2,3,5-Triiodobenzoic Acid and Indole Acetic Acid on Growth and Development of Impatiens balsamina during Different Photoperiods

This paper deals with the effect of 100 mg/1 each of GA₃ TIBA and IAA singly and in combination with each other on stem elongation, development of lateral branches and floral bud initiation in Impatiens balsamina plants exposed to 8-, 16- and 24-h photoperiods. GA₃ enhances stem elongation, the enhancing effect decreasing with IAA as well as with TIBA during 8-h but increasing during 16- and 24-h photoperiods. It decreases the number of lateral branches, the decrease being greatest during 16-, less during 8- and the least during 24-h photoperiods. The time taken for floral buds to initiate with and length of branches during 16-h photoperiods. During 8-h photoperiods, IAA delays the initiation of floral buds, while GA₃ hastens it when used together with TIBA or IAA or both. GA₃ increases the number of floral buds on the main axis but decreases it on lateral branches, while TIBA decreases the number on the main axis but increases it on lateral branches. IAA reduces the number of floral buds on the main axis only when used alone, but on both the main axis as well as on lateral branches when used together with GA₃ and TIBA. Floral buds were not produced on lateral branches when plants were treated with GA₃, TIBA and IAA all together. GA₃ and TIBA induced floral buds even under non-inductive photoperiods, the number of buds and reproductive nodes being less in TIBA- than in GA₃-treated plants during 24-h photoperiods. The time taken for floral buds to initiate with GA₃ and TIBA during noninductive photoperiods is much longer than that during 8-h inductive photoperiods with or without GA₃ or TIBA application. IAA completely inhibits the GA₃- and TIBA-caused induction during 24-h, but only delays it and reduces the number of reproductive nodes and floral buds during 16-h photoperiods.     

The Effect of Gibberellic Acid and Guanosine Monophosphates on Extension Growth, Leaf Production and Flowering of Impatiens balsamina

Gibberellic acid (GA₃) increases the height of Impatiens balsamina under both 8- and 24-h photoperiods. The height also increases with all guanosine monophosphates (GMPs) under 8-h photoperiods but only with 5′-GMP under 24-h photoperiods. GA₃ as well as GMPs increase the number of leaves under 8-h but not under 24-h photoperiods. GA₃ as well as GMPs induce floral buds under strictly non-inductive photoperiods and increase the number of floral buds under 8-h photoperiods. The floral bud initiation occurs earlier when cGMP is used in combination with 100 mg/l GA₃.     

Effect of GA3 and AMPs on the activities and electrophoretic patterns of acid and alkaline phosphatases in relation to flowering ofImpatiens balsamina L.

GA₃, cyclic AMP as well as 3′-AMP and 5′-AMP induced the formation of floral buds inImpatiens balsamina under strictly non-inductive photoperiods. While photoperiods and treatments with GA₃ or AMPs did not much affect acid phosphatase activity, AMPs increased the activity of alkaline phosphatase both in the stem and the leaves under both photoperiods. The phosphatase activity of the water- and GA₃-treated plants under inductive photoperiods was higher than that of the plants of the respective treatments under non-inductive photoperiods. GA₃ as well as all the three AMPs induced both in the stem and the leaves the formation of new isoenzymes of both these enzymes under both photoperiods.     

Effect of gibberellic acid and salicylic acid on the activity and electrophoretic pattern of IAA-oxidase during floral induction inImpatiens balsamina

IAA-oxidase activity increased in the stem as well as in the leaves of plants treated with GA₃, SA and GA₃ + SA during the early stages under inductive and non-inductive photoperiods, the activity being the highest in GA₃ + SA-treated plants. An isoenzyme of IAA-oxidase with Rm 0.15 developed in the stem as well as in the leaves subsequent to 1 or 2 inductive treatments. As this band persisted till the end of the experiment, it may be associated with the initiation as well as development of floral buds. Another band (Rm 0.30) appears to be associated with the phenol (SA) as it developed in the stem as well as in the leaves of SA- and GA₃ + SA-treated plants under both photoperiods. A band with Rm 0.60 developed in the leaves but not in the stem of GA₃-, SA- and GA₃ + SA-treated plants under both photoperiods.     

Effect of ínductive photoperiod and gibberellin treatment on peroxidase enzyme system in relation to floral induction inImpatiens balsamina L

Gibberellins A₃ and A₁₃ cause floral induction inImpatiens balsamina, a qualitative short day plant, under non-inductive 24-h photoperiods (continuous illumination). However, the influence of the two inductive factors,i.e. gibberellins and short days (8-h photoperiods) on the peroxidase enzyme system is different. The total peroxidase activity decreases under both inductive and non-inductive photoperiods, with or without gibberellin treatment. The electrophoretic pattern of isoperoxidases changes only in response to gibberellin treatment. Under 24-h photoperiods, treatment with gibberellins A₃ and A₁₃ causes the appearance in the stem of three additional isoenzymes of peroxidase (Rm 0.50, 0.71 and 0.76). These bands do not appear in the leaves, which are non-essential for gibberellin-caused floral induction in this plant. Under 8-h photoperiods also, gibberellins induce the appearance of new isoenzyme bandsi.e. two in the stem (Rm 0.50 and 0.76) and one in the leaves (Rm 0.05). These may be correlated with the synergistic increase in the number of floral buds in these plants in response to simultaneous exposure to two inductive factors.     

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.     

Gibberellic acid- and salicylic acid-caused formation of new proteins associated with extension growth and flowering ofImpatiens balsamina

GA₃ as well as SA increase the protein content of the stem and the leaves at 1 day under both 8- and 24-h photoperiods. A new protein band with Rm 0.47 seems to be associated with floral bud initiation as it develops within 1–3 days in the stem as well as in the leaves of plants exposed to inductive treatments regardless of whether the induction is caused by 8-h photoperiods or by treatment with GA₃ of SA under 24-h photoperiods. Another band with Rm 0.23 developed only in the stem of water-as well as GA₃- or SA-treated plants under 8-h photoperiods. It may possibly be associated with extension growth.     

Effect of Gibberellic Acid and Some Phenols on Flowering of Impatiens balsamina, a Qualitative Short-day Plant

GA₃ as well as SA (salicylic acid) and β-N (β-naphthol) induce floral buds in Impatiens balsamina under strictly non-inductive photoperiods. The floral bud initiation is accelerated when 1 mg/1 SA is used in combination with 100 mg/1 GA₃. 100 mg/1 GA₃+ 1 mg/1 SA and 100 mg/1 GA₃+ 100 mg/1 β-N increase the number of floral buds as compared with 100 mg/1 GA₃ alone.     

Genetic Regulation of Development in Sorghum bicolor: IV. GA(3) Hastens Floral Differentiation but Not Floral Development under Nonfavorable Photoperiods

Sorghum bicolor (L.) Moench lines with genetic differences in photoperiod requirement were planted in the field near Plainview, Texas (about 34° northern latitude) around June 1 and treated with gibberellic acid (GA₃) solutions applied in the apical leaf whorl. GA₃ hastened the date of floral differentiation (initiation). The greatest responses to GA₃ were by 90M and 100M, the latest of the genotypes, for which floral initiation dates were hastened an average of 19.5 and 21.7 days, respectively, for the 4 years beginning in 1980. There were very small differences in dates of anthesis between control and GA₃-treated plants. Microscopic examination of apical meristems collected between the date of floral initiation of GA₃-treated plants and the later date of initiation of control plants revealed: (a) several morphological characteristics of floral differentiation in the apical meristem of treated plants, (b) consistent occurrence of vegetative morphology in control plants, (c) a few meristems from GA₃-treated plants that appeared to be regressing in floral development and thus possibly exhibiting dedifferentiation. Dedifferentiation of prepanicle primordia into leaves would explain the observed equal or greater number of leaves in GA₃-treated plants rather than the expected smaller number. It is apparent that the presence of a morphological differentiated floral meristem in sorghum does not drive subsequent floral development in the absence of inductive photoperiods. This further suggests that initial floral differentiation and subsequent floral development may be controlled separately in sorghum.     

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; )     

Effect of varying lengths of inductive and supplementary non-inductive photoperiods on vegetative growth and flowering of Impatiens balsamina

The photoperiodic requirement for flowering in Impatiens balsaminachanges with the length of the photoperiod. Floral buds wereinitiated with two 8 hr but with four 15 hr photoperiods andflowers opened with four 8 hr but twenty-eight 15 hr photoperiods.A part of the photoperiodic requirement for floral inductionin this plant can be substituted by LDs containing 4 or morehours of darkness (10). It indicates the identical nature ofthe floral stimulus produced during the dark period, whetherit forms a part of the inductive or non-inductive cycles. Theeffect of these supplementary non-inductive photoperiodic cyclesin causing floral bud initiation also depends on the lengthof the first inductive obligatory cycle. More floral buds andflowers were produced on plants exposed to 15 hr than 8 hr photoperiods,probably due to the higher number of leaves that were producedunder the former condition of weaker induction. The shorterthe dark period in the photoperiodic cycle, the weaker the induction,the slower the rate of extension growth but the more differentiationof leaves. ¹ Present address: Department of Biology, Guru Nanak Dev University,Amritsar-143005, India. (Received November 9, 1977; )     

Effect of Gibberellic Acid and Phosfon on the Critical Dark Period Reqnirement for Flowering of Impatiens balsamina cv. Rose

The critical dark period requirement for flowering of Impatiens balsamina L. cv. Rose, an obligate short day plant, is about 8.5 hours. While GA₃ completely substituted for the dark period requirement, Phosfon prolonged it to 9.5 hours. GA₃ hastened and Phosfon delayed the initiation of floral buds under all photoperiods. Floral buds opened into flowers only during 8 and 14 hour photoperiods in control and Phosfon-treated plants but during all photoperiods in GA₃-treated ones. The delay in floral bud initiation and flowering was correlated with shifting up of the node bearing the first floral bud and flower respectively. While GA₃ increased the numher of floral buds and flowers in all photoperiods except 8-hour, Phosfon increased their number in the 14-hour photoperiod only. The number of flowering plants decreased with increasing photoperiod regardless of GA₃ and Phosfon application. The effect of Phosfon was completely or partially overcome, depending upon the photoperiod, by simultaneous application of GA₃.     

Effect of Gibberellic Acid and Monophenols on Flowering of lmpatiens balsamina in Relation to the Number of Inductive and Non-inductive Photoperiodic Cycles

A single treatment of plants with GA₃ (gibberellic acid) is not adequate to cause induction under LD (long day: 24-h photo-period) condition, but its effect is added to the sub-threshold induction caused by one SD (short day: 8-h photoperiod) cycle. Floral bud initiation is hastened, and the number of floral buds and flowers per flowering plant increases in plants receiving a single treatment with the combination GA₃+ SA (salicylic acid) accompanying a single SD cycle. However, the increase on 10 replicate basis is more marked in plants receiving three treatments with the combination GA₃+β-N (β-naphthol) and five treatments with the combination GA₃+ SA accompanying six and 10 SD cycles, respectively. The number of floral buds and flowers decreases with an increase hi the number of SD cycles, but it is higher in plants treated with GA₃, SA or GA₃+β-N than in the water-treated controls. — Under long days, treatment of plants with the combinations GA₃+ SA or GA₃+β-N accelerates the initiation as well as increases the number of floral buds. While a minimum of five treatments with GA₃ or of 25 with SA or β-N alone is needed for floral bud initiation under a 24-h photoperiod, three treatments are adequate to induce floral buds with the combination GA₃+ SA or GA₃+β-N under continuous illumination. Ten or more treatments with these combinations under a 24-h photoperiod produce more flowers than the same treatments under an 8-h photoperiod.     

Specific proteins in stem meristems during transition to flowering

Immunodiffusion tests were used for studying protein composition of apical buds ofRudbeckia bicolor andPerilla nankinensis during their transition from vegetative to reproductive state under inductive photoperiodic conditions or GA₃ treatment. In both species the induced buds differ from the vegetative ones in the presence of specific proteins (P): P1, P2, P3 appear inRudbeckia apical buds 2, 8, 16 d after the start of inductive treatment; P4 appears inPerilla apical buds 6 d after inductive treatment. P1, P2, P4 are revealed in induced buds in the early period of apex development when morphogenetic changes are not yet present. The similarity between antigenic spectra of induced buds and of those treated by GA₃ appears only inRudbeckia. These observations support the hypothesis of a change in gene expression at floral evocation. Presented at the International Symposium “Plant Growth Regulators” held on June 18–22, 1984 at Liblice, Czechoslovakia.     

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.     

IAA-oxidase in Impatiens balsamina Affected by GA3 and Tannic Acid

The activity of IAA-oxidase increased in the leaves of Impatiensbalsamina plants receiving inductive photoperiodic cycles andin plants receiving treatments with gibberellic acid (GA₃) and/ortannic acid (TA), even under non-inductive photoperiods; theactivity also increased in the stem receiving inductive photoperiodiccycles (8 h). Treatment with GA₃ and TA mimics the effect ofSD cycles in the development of some isoenzymes of IAA-oxidase.Thus a new isoenzyme at R_f 0.48 developed in the leaves andone at R_f 0.82 developed in both the stem and the leaves ofall plants receiving inductive treatments – photoperiodicor chemical – but not in water-treated controls undernon-inductive photoperiods. Another isoenzyme at R_f 0.68 developedonly in the stems. Flowering, gibberellic acid, IAA oxidase, Impatiens, phenols, photoperiod     

Promotory effect of GA13 on flowering ofAmaranthus — a short day plant

Abstact The three plant types ofAmaranthus namely,A. caudatus f.albiflorus, A. caudatus f.caudatus andA. tricolor var.tristis are qualitative short day plants with critical photoperiods 16.0, 15.5 and 15.0 h, respectively. Gibberellins A₃, A₄₊₇ and A₁₃ affect extension growth, leaf differentiation and floral induction differently. Thus, in all the three plant types ofAmaranthus, whereas, GA₃ and G₄₊₇ enhanced extension growth, GA₁₃ was completely ineffective under both, 24- and 8-h photoperiods. None of the three gibberellins could affect the leaf differentiation. In all the three plant types, flowering was promoted by GA₁₃ and not by other gibberellins tried. GA₁₃ caused promotion was manifested in two manners, firstly by lowering the critical dark period requirement in each inductive cycle, and secondly by shortening the total period taken for the initiation of inflorescence primordia under inductive photoperiods. The floral induction by gibberellins inAmaranthus is contrary to the gibberellin-anthesin concept of Chailakhyan. It is suggested that gibberellins other than GA₃ may be playing an important role in floral morphogenesis of short day plants.     

Effect of Morphactin, Gibberellic Acid and Auxin and on Growth and Development of Bryophyllum tubiflorum

six month old LD- and SD- grown plants of Bryophyllum tubiflorum were treated with morphactin (n-buty1-9-hydroxy-fluorene-(9)-carboxylate), singly and in combination with GA₃ and IAA. Morphactin and IAA decreased stem elongation and number of leaves, the effect increasing with concentration concentation. Morphactin also caused lateral buds to develop into branches and the fusion of upper leaves to form structures of different shapes. GA₃ enhanced stem elongation, increased leaf number and induced floral buds under SD conditions. It reversed the inhibitory effect of morphactin on stem elongation, leaf number and leaf fusion and also restored apical dominance when applied simultaneously with morphactin. The stimulaneous application of IAA also reversed the morphactin effects on leaf fusion and on apical dominance. The results have been discussed in the light of literature available on the subject.     

The Effect of Flower Induction on the Rate of Leaf Initiation

Vegetative plants of four short-day and five long-day specieswere exposed to inductive or non-inductive daylengths continuously,or to inductive conditions for just long enough to induce flowering.One day-neutral species was given long days throughout the experiment.The rate of leaf initiation was significantly greater in floweringthan in vegetative shoots in all photoperiodically sensitivespecies following induction until the formation of a terminalflower. A significant increase in the rate of leaf initiationwas also noted when floral initials began to appear in the day-neutralspecies. It is concluded that floral induction and stimulationof leaf initiation are likely to be universally associated whetherspecies are photoperiodically sensitive or not. It is also suggestedthat, together with apical elongation and early developmentof axillary buds, this stimulation is an essential step in themorphological sequence by which flower initials are produced.