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.     

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 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.     

Flowering in Pisum: the Effect of Genotype, Plant Age, Photoperiod, and Number of Inductive Cycles

The genotypes If e Sn hr, Lf e Sn hr, and If e Sn Hr requirefewer inductive cycles as they age. It is suggested that thisresults from a decrease in the activity of the Sn gene in theleaves as they age, resulting in a higher ratio of promoterto inhibitor. Gene Lf does not affect the rate of this agingbut it does increase the number of inductive cycles requiredfor flower induction over the first 5 weeks of growth. The geneHr has no effect until week 4 but thereafter causes a reductionin the effect of age on the Sn gene. The genotype If e Sn Hrcan be induced by a single inductive cycle (32 h of light) fora relatively long period. The length of dark period required for the expression of theSn gene is shown to be less than 4 h providing a relativelylong photoperiod precedes the dark period. It appears that noper manent induction of tissue by photoperiods favourable toflowering occurs in peas. The critical photoperiod for plantsof genotype if e Sn Hr is shown to be between 12 and 14 h atl7·5 °C and the usefulness of the term ‘criticalphotoperiod’ is discussed with respect to quantitativelong-day plants.     

The Effect of Gibberellic Acid on the Flowering of Spring and Winter Rye

The effects of leaf applications of gibberellic acid on theflowering of unvernalised and partially vernalised winter ryeand on spring rye have been investigated. A small stimulationof the progress to flowering was obtained but it was subsequentlylost over a period of seven or eight weeks. The stimulationwas not due to a reduction in the vernalisation requirementof the winter variety since similareffects were obtained inspring rye. Treatment with gibberellic acid stimulated meristems of boththe vegetative and reproductive parts of the rye plant. Thehastening of development of floral primordia was consideredto be part of this overall stimulatory effect, which is concernedwith growth rather than with development. The relation between these results and the influence of gibberellicacid on the flowering of some other long- and short-day plantsis briefly discussed.     

Effect of Number of Photoperiodic Cycles on Flowering and Fruiting in Early and Late Varieties of Okra (Abelmoschus esculentus (L.) Moench.)

Early and late varieties of the short day plant, Abelmoschusesculentus (L.) Moench. (= Hibiscus esculentus L.), were subjectedto various numbers of short days (SD; 10 h natural daylight)before transfer to 16 h long days. Short day treatments werestarted at the time of cotyledon release following seed germination,and their effects on the induction and development of flowersand fruits were recorded. While early okra required 6 SD cyclesfor the induction of flowering in all plants, late okra required14. However, both varieties needed more than 20 SD cycles forflower opening; flower buds produced by plants given fewer SDcycles abscinded with little or no development. In both varieties,the number of flower buds produced on each plant increased asthe number of short day cycles was increased from 5 to 20; flowerbuds were initiated at more axillary bud sites on the main stem.Three fruits were formed on each plant of both varieties subjectedto more than 30 SD cycles but, while the last formed fruit abscindedwithout development, the other two developed and became filledwith seeds. However, the greatest yield in fruit dry weightwas from plants kept under SD throughout and also in late okraplants given 55 SD. In general, the total number of seeds perplant increased as a larger number of SD cycles were imposed.     

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 Single and Repeated Gibberellic Acid Treatment on Internode Number and Length in Dwarf Peas

In long-term experiments comparing the results of single and repeated treatment of dwarf peas with gibberellic acid, both once-treated and weekly-treated plants formed more internodes than control plants. The initial high rate of internode formation in the once-treated peas dropped rapidly reaching that of control plants three weeks after treatment. Weekly-treated plants maintained a higher rate of internode formation. The ratio of internode lengths of once-treated plants to control plants was high (over 3) for the internodes which were elongating during or shortly after the single treatment but dropped rapidly and approached unity in later-developed internodes. The ratio of internode lengths of weekly-treated plants to control plants continued to be high throughout the experiment.     

Photoperiodic studies on growth and development of Impatiens balsamina L.

Summary Seedlings of Impatiens balsamina raised under ND and LD conditions were divided into two sub-groups each when they had reached 5-leaf stage. While one sub-group was left under the same condition (NDND or LDLD), the other was transferred to the other photoperiod (NDLD or LDND). NDND plants were subdivided into 2 lots. One of these was transferred to SD in May. The dates of emergence of individual branches and floral buds were recorded and the vegetative period was calculated in each case.It was found that in NDND plants floral buds were produced from all the nodes except the lowermost which produced a single vegetative branch. In LDND plants the vegetative branches were produced from the lower 9 nodes but floral buds from those above these. Small leafy structures which ultimately dried up were produced from a few top nodes in both these cases. In contrast to this in LDLD plants only vegetative branches were produced from all the nodes. In NDLD plants floral buds were produced from the lower 3–5 nodes prior to transfer to LD condition, but vegetative branches were produced from the upper nodes after this transfer. Even some of the lower floral buds reverted to vegetative state under this condition.The production of floral buds or the vegetative branches as the case may be, occurred in acropetal succession under all the photoperiodic conditions and never in basipetal manner.LDLD and NDLD plants, which did not flower at all, continued to produce lateral branches without showing any sign of senescence, while LDND and NDND ones showed yellowing of the apical growing point which spread downwards and lead ultimately to the death of the plant. The senescence was hastened when these plants were transferred to SD condition towards the end of May. The senescence therefore, appears to be related with reproductive development. The results are discussed in the light of current literature.     

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.     

Embryo Development in Ripe Seeds of Eranthis hiemalis and its Relation to Gibberellic Acid

The ripe seeds of Eranthis hiemalis (L.) Salisb., the winter aconite, contain undeveloped embryos. At 20–25°C the embryos grow only little, and the seeds do not germinate. Rapid embryo development starts if the seeds, after 3 weeks of “after-ripening” at 20–25°C, are placed at low temperature, 3–4°C; germination then takes place after 2–3 months, Embryo development without germination occurs when the seeds are placed in gibberellic acid solutions at 20–25°C. Embryo development is inhibited at low temperature by the specific inhibitor of gibberellin biosynthesis, 2-chlorethyl cholin chloride, but is restored by the simultaneous addition of gibberellic acid. It is suggested that one early effect of the cold is to bring about a synthesis of gibberellin.     

Studies on the Post Flowering Photoperiodic Responses in Soybean

Typical varieties from the main ecological regions and of different maturity stages in China were chosen for studying the post-flowering photoperiodic responses to day length in soybean (Glycine max (L.) Merr. ). The results indicated that the response to post-flowering photoperiod existed among all varieties with different maturity stages. The response was not due to of temperature effects, duration of photosynthesis or pre-flowering 15hotoperiodic after-effect Instead, it was typical photoperiodism. The response was found not only at the stages of flowering and podding but also at the stage of seed filling. Experimental results proposed that the photoperiodic demand for flowering and fruiting in soybean was a continuous process. The regulation of photoperiod on growth lasted from emergence of seedlings to maturation. There were some common basis in photoperiodic effects on both flowering induction and maturation promotion. However, the effects of photoperiodic induction had after-effect and were reversible.     

Effects of Exogenous Amino Acids on Iron Uptake in Relation to their Effects on Photoperiodic Flowering in Lemna paucicostata 6746

The flowering of Lemna paucicostata 6746 grown on 14-h photoperiodwas enhanced by the addition of high concentrations of ironto the medium, which also increased the endogenous iron concentration.The addition of asparagine, aspartate, glutamate, -alanine,glycine or serine to the medium also increased the endogenousiron level, resulting in the promotion of flowering. In contrast,the addition of cysteine, cystine, glutamine, arginine, threonineor phenylalanine lowered the endogenous iron level, resultingin the inhibition of flowering. Glycine and asparagine added to the medium during an inductive96-h dark period did not promote iron uptake and had no effecton flowering, but when added during the subsequent 120-h lightperiod, they promoted both iron uptake and flowering response.The increase in the endogenous iron level seems to favor floraldevelopment rather than induction of photoperiodic floweringof Lemna paucicostata 6746. (Received September 8, 1986; Accepted March 31, 1987)     

The Effect of Gibberellic Acid on Fibre-cell Length

Measurements were made of fibre-cells from plants of Corchorusolitorius L., Hibiscus cannabinus L., and Cannabis sativa L.Which had been sprayed with gibberellic-acid solution. Fibre-cellsfrom treated plants showed a highly significant increase inlength, 20–130 per cent, for the whole stem and as muchas 400 per cent. for a single intermode. Gibberellic acid increased the variation in cell-length andthe positive skewness of the distribution of the variate. Differences in cell-length can be related to the developmentalsequence of the shoot and the variation in internode-length.