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.     

Fluctuation of free IAA under inductive and non-inductive photoperiods in Chenopodium rubrum

Fluctuation in levels of endogenous free IAA has been followed in the SD plant Chenopodium rubrum under photoperiodic conditions inductive or not inductive of flowering. Endogenous IAA was measured fluorimetrically as -pyrone. The level of IAA shows little fluctuation under continuous illumination. An endogenous rhythm of IAA fluctuation was found in plants transferred from light to continuous darkness, with a natural period of 30 hrs. The troughs of minimum IAA level within the endogenous rhythm coincided with the peaks in the endogenous rhythm of flowering response, which possessed the same period length. The concentration of IAA in the shoot always decreased at the end of cycles of dark period that induce flowering. The results are discussed in relation to the role of IAA in flowering of SD plants.     

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; )     

Gel electrophoretic studies of proteins in photo-induced and vegetative plants of Impatiens balsamina

In Impatiens balsamina L. var. Rose, a qualitative SD plant,the protein content of the leaves shows an upsurge at the timeof physiological induction. The electrophoretic pattern of watersoluble proteins, however, does not change except for a newprotein that appears in the stem after the plants have received1 SD cycle. ¹Present address: Department of Biology, Guru Nanak Dev. University,AMRITSAR (Punjab) 143005, India. (Received March 1, 1976; )     

Induction of flowering in the duckweed Lemna paucicostata under non-inductive photoperiods by tannic acid

Flowering in Lemna paucicostata 6746 could be induced by tannic acid under strictly non-inductive photoperiods. This polyphenol completely abolished the photoperiodic sensitivity of strain 6746 as flowering could also be obtained under continuous light (nearly 80% flowering was recorded in the plants supplied with 10⁻⁵ tannic acid). Though its mode of action is unknown, tannic acid is unlikely to act as a gibberellin-antagonist in its effect on flowering in strain 6746.     

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.     

Effect of flowering on vegetative growth and further reproduction in

Flowering intensity and plant size were monitored in 155 Festuca novae-zelandiae individuals over four years to determine if trade-offs exist between inflorescence production and vegetative growth, and between inflorescence production in different years. Less than half of the population flowered in any one year, 36% of individuals did not flower at all, and only 17% flowered in all four years of the study. Mean number of inflorescences per individual per year varied from 1.54 to 5.53 (maximum = 85). No trade-offs were detected between flowering frequency and intensity; individuals that flowered more frequently also produced more inflorescences in each flowering episode. No trade-off was detected between current and future reproduction, rather flowering intensity was positively correlated between years. Growth, as measured by diameter increment, was positively related to flowering frequency and flowering intensity, both across all individuals studied and within 1m x 1m plots. The presence of a positive relationship between growth and reproduction within plots argues against meso-scale variability in environment factors being the cause of the results from analyses involving all individuals. Clearly reproduction in F. novae-zelandiae does not incur a marked cost in growth or future reproduction. The assumptions underlying theoretical expectations of such trade- offs may not be valid for long-lived clonal plants such as F. novae-zelandiae.     

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 morphactin on peroxidases and its relationship to rooting hypocotyl cuttings of Impatiens balsamina

Morphactin inhibited the production of roots on hypocotyl cuttingsof Impatiens balsamina with intact apex and cotyledons. Rootswere, however, initiated when cuttings were transferred to water.A new peroxidase isoenzyme in the cotyledons and two in thehypocotyls that were absent in controls, appeared in morphactin-treatedcuttings. However, one isoenzyme in the cotyledons and threein the hypocotyls that were absent in morphactin-treated cuttings,were detected in the controls. These isoenzymes may be involvedin the initiation and development of roots. (Received August 15, 1972; )     

Effect of cycloheximide on GA3 response and on photoperiodic reactions of Impatiens balsamina L.

GA₃ increased the extension growth of Impatiens balsamina L.till 56 days under 8- and 24-h photoperiods. Cycloheximide whichdecreased height slightly under inductive conditions at a laterstage did not affect the GA₃-promoted extension growth. BothGA₃ and cycloheximide caused enhancement of the rate of differentiation,although this effect was temporary in the case of GA₂. Cycloheximidedoes not affect photoperiodic induction, whereas it hastensand increases the magnitude of GA₂-induced flowering.     

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.     

Determination and Differentiation of Leaf and Petal Primordia in Impatiens balsamina

The development of primordia as leaves, petals, or as organsintermediate between leaves and petals can be regulated by photoperiodin Impatiens. In intermediate organs only some parts of theorgan differentiated as petal, and then only in some cell layers.Allometric measurements of primordium shape suggested that intermediateorgans may begin development as petals, and that their intermediatecharacter at maturity resulted from a switch of some parts ofthe organs from petal to leaf development when the primordiawere between 0.5 and 1 mm long. In reverted apices made to re-flower,primordia were not completely determined as leaves until theywere about 750 µm long. Determination typically occurredfirst at the tips and last at the bases of these primordia.The determination of primordia as leaves or petals in Impatiensis discussed in relation to primordium determination in otherspecies. It is suggested that the lack of commitment to flowermay result in relatively late primordium determination in Impatiens. Impatiens balsamina, determination, differentiation, leaf and petal development, flowering, reversion     

LEAFY, TERMINAL FLOWER1 and AGAMOUS are functionally conserved but do not regulate terminal flowering and floral determinacy in Impatiens balsamina

In Impatiens balsamina a lack of commitment of the meristem during floral development leads to the continuous requirement for a leaf-derived floral signal. In the absence of this signal the meristem reverts to leaf production. Current models for Arabidopsis state that LEAFY (LFY) is central to the integration of floral signals and regulates flowering partly via interactions with TERMINAL FLOWER1 (TFL1) and AGAMOUS (AG). Here we describe Impatiens homologues of LFY, TFL1 and AG (IbLFY, IbTFL1 and IbAG) that are highly conserved at a sequence level and demonstrate homologous functions when expressed ectopically in transgenic Arabidopsis. We relate the expression patterns of IbTFL1 and IbAG to the control of terminal flowering and floral determinacy in Impatiens. IbTFL1 is involved in controlling the phase of the axillary meristems and is expressed in axillary shoots and axillary meristems which produce inflorescences, but not in axillary flowers. It is not involved in maintaining the terminal meristem in either an inflorescence or indeterminate state. Terminal flowering in Impatiens appears therefore to be controlled by a pathway that uses a different integration system than that regulating the development of axillary flowers and branches. The pattern of ovule production in Impatiens requires the meristem to be maintained after the production of carpels. Consistent with this morphological feature IbAG appears to specify stamen and carpel identity, but is not sufficient to specify meristem determinacy in Impatiens.     

Influence of different Inocula of Meloidogyne arenaria on plant growth parameters and nematode multiplication in balsam (Impatiens balsamina)

Pathogenic effect of root-knot nematode Meloidogyne arenaria was studied on balsam (Impatiens balsamina) by inoculating the different inoculum levels of root-knot nematode. It was observed that the inoculum levels up to 2000 J₂ of root-knot nematode did not show significant reduction in plant growth characters as compared to control. Although the significant reduction in plant growth characters was recorded at and above 3000 J₂ of root-knot nematode, progressive increase in the host infestation as indicated by the number of galls as well as the population of root-knot nematode was recorded with an increase in the level of inoculum. However, the rate of nematode multiplication was reduced with the increase in the inoculum density of M. arenaria. It can be concluded from these results that the damaging threshold level of M. arenaria on balsam was found to be as 3000 J₂/plant.     

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.     

The action of skeleton photoperiods on flowering in Lemna perpusilla

The effects of 24 hr cycle skeleton photoperiodic schedulesinvolving two short light pulses on flowering in Lemna perpusillahave been studied. Simulation of complete photoperiods by correspondingskeletal ones is nearly perfect for all photoperiods up to 8hr and is unstable for periods of 9 to 13 hr. A jump in theresponse phase appears when skeleton photoperiods ranging from12 to 13hr are given. For all skeleton photoperiods longer than14 hr the phase is entrained so that it agrees with that givenby skeleton photoperiods of complemental lengths. That is, askeleton photoperiod of 18 hr is equivalent to that of 6 (=24–18) hr. Simulation is largely related to whether thesecond pulse is locked on to "dawn" or to "sunset" dependingon when it falls during the dark period following the firstpulse. The inductive action of skeleton photoperiods that gives unstableentrainment depends on the length of a preliminary dark periodgiven before the plant receives the first pulse, since in theseskeleton schedules the sensitive zone to the second pulse shiftswith the length of the preliminary darkness. Thus, we tentatively conclude that the circadian oscillationin L. perpusilla involves an entrainment mechanism and thatphotoperiodic induction is contingent on the coincidence oflight and a specific inductive phase in oscillation. (Received September 18, 1968; )     

Effect of adenosine monophosphates on the flowering of Impatients balsamina L., a qualitative short-day plant

Summary Adenosine monophosphates (AMPs) cause the induction of floral buds in Impatients balsamina L. under strictly non-inductive photoperiods and hasten it under inductive photoperiods, cyclic AMP being more effective than 3- or 5-AMPs in this regard.Abbreviations cyclic AMP cyclic 3,5-adenosine monophosphate     

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.