Floral Bud Formation Research Articles

Seasonal Changes of Mineral Nutrient Concentrations of Leaves and Stems of ‘Kinnow’ Mandarin Trees in Relation to Alternate Bearing

The relationship between alternate bearing and the variation of mineral nutrient content in the leaves and stems of ‘Kinnow’ mandarin trees (Citrus reticulata Blanco) and the effects of these relationships on flower bud formation were investigated. Mineral content was determined in the leaves and stems of “on” and “off”-year trees at 1-month intervals from November until March, coinciding with the floral bud formation stages of citrus trees. The results showed that the presence of fruits consistently inhibited flower bud formation, decreased the number of sprouting buds, and reduced the vegetative growth of trees. Fruiting state had a significant effect on the content of P, K, and Mg in both leaves and stems, but did not affect the amount of N in these two organs. Leaf and stem P and K contents were greater in “off” than in “on” trees, but Mg content was higher in “on” than in “off” trees. Mandarin fruits were acting as very strong sinks for potassium and phosphorous. Thus, K and P levels in “on” trees decreased to deficient levels, and therefore, a sufficient supply of these two elements is a key to a successful commercial annual production. Seasonal variations in leaf and stem micronutrient contents were neither uniform nor affected by the fruiting state of trees.

Effects of soil water deficits on three genotypes of potted Campanula medium plants during bud formation stage

Abstract: Potted ornamental plants are often exposed to drought stress during shipping and retailing, which decreases the value and postharvest quality. Thus, selection of genotypes which can better withstand soil water deficits is essential for sustainable production. Here, the response of three genotypes of potted Campanula medium (denoted as G100, G102 and G104) to progressive soil drying was investigated and their post-production performance was evaluated for four weeks. The potted plants were grown in a climate controlled greenhouse and were either well-watered (W) or drought-stressed (D) at floral bud formation stage. Soil water status was expressed as the fraction of transpirable soil water (FTSW). In the D pots, FTSW declined fastest in G100, followed by G102, and slowest in G104 after withholding irrigation. In the W plants, stomatal conductance ( g s ) was similar among the three genotypes, whereas transpiration rate ( T ) differed significantly among genotypes and was highest for G100, intermediate for G102, and lowest for G104. Estimated by a linear-plateau model, g s and T of G100 started to decrease at significantly higher FTSW thresholds than did G102 and G104. An earlier closure of stomata and decrease of T in G100 would allow the plant to conserve water in the soil; however, owing to its putative larger leaf area and greater stomatal density on the adaxial leaf surface, G100 quickly depleted soil water and resulted in severe drought stress to the plants as exemplified by the significantly lowered g s , leaf area, and relative water content (RWC). In contrast, a smaller leaf area and a lower stomatal density on the adaxial leaf surface of G104 enabled the plants to slowly deplete soil water and maintain high g s , T , leaf area, and RWC 8 days after withholding irrigation. Coincided with these, the floral bud abortion rate in the D plants was significantly higher for G100 as compared with G102 and G104. It is concluded that in potted ornamentals, a low transpiration rate, hereby a slow rate of soil water depletion, is crucial for maintaining postharvest quality under drought stress.

The Photoperiod-regulated Bud Formation of Red Pitaya (Hylocereus sp.)

Red pitaya (Hylocereus sp.), which flowers between May and October and sprouts between November and May in Taiwan, has been confirmed to be a long-day plant. The areoles on the old shoots may be induced to flower after the March equinox naturally, and the floral bud formation occurs in two to three waves from May to October. We conducted experiments on photoperiodic regulation of floral bud formation from June to Dec. 2009 and tested the feasibility of off-season production in 2011. Shortening summer daylength to 8 h inhibited the areoles at the distal end of the shoots to develop into floral buds and promoted sprouting at the proximal ends of the shoots. Night-breaking treatment between the September equinox and the winter solstice led to floral bud formation. The critical daylength seemed to be ≈12 h, and night-breaking treatment would be applicable between the September and the next March equinoxes to produce off-season crops. The duration of night-breaking required for flower differentiation was longer in the cooler than in the warmer season. Four weeks of night-breaking treatment was sufficient to promote flowering in late fall (mid-October to mid-November), but 3 months were required to generate similar result in the winter and early spring (January to March) in southern Taiwan.

Desarrollo reproductivo del “amancay” Ismene amancaes (Amaryllidaceae) en su ambiente natural

Ismene amancaes “amancay” is a bulbose species typical of the central coast vegetation of Peru called “lomas”. This species sprouts in June during the beginning of the winter-fog period. It has large yellow, aromatic flowers valued for their ornamental value. Our goal was to examine the reproductive development of Ismene amancaes in its natural environment, and we recorded monthly observations during a yearlong study. Observations of the interior of the bulbs allowed recording of the beginning of floral bud formation and development, relating them to leaf formation and edaphic humidity. We found that the first floral buds develop the year before their emergence in December, reaching a maximum number of floral buds in February, during the Summer. Floral bud differentiation starts after leaves that will emerge the following year have developed. This occurs during a period of maximum decrease in edaphic humidity and an increase in air temperature (November). The inflorescence is the only branching that develops while the apical bud continues developing leaves. In June, the small inflorescence reaches the neck of the bulb and surpasses it followed by those leaves developed before the inflorescence that surround both the inflorescence and the apical foliar bud. The foliar bud will continue its development, and in July two of the leaves expand, while the smaller ones remain inside the bulb until the following year’s Lomas season. It can be noted that the reproductive success of Ismene amancaes in its initial development depends on the photoreserves accumulated in the bulb the previous growth period.

EFFECTS OF LIGHT QUALITY UNDER RED AND BLUE LIGHT EMITTING DIODES ON GROWTH AND EXPRESSION OF FBP28 IN PETUNIA

Floral induction in Arabidopsis is influenced by blue and red light. In this study, we investigated the effects of light quality from different types of light emitting diodes (LED) on growth and floral induction in petunia (Petunia hybrida Vilm.) ‘Baccarat blue’, as well as the expression of the SOC1-like gene FBP28. Petunia plants with five true leaves were exposed to fluorescent lamps, red or blue LED after transplanting to a growth cabinet. The photoperiod was 14 h and the irradiance was adjusted to 100 µmol·m -2 ·s -1 (PPF) around the shoot apices. At the 53 rd day after, petunia plants under red LED showed lower plant height than the other treatments. The number of leaves and length of lateral shoots increased under red LED, and the shoot length became about 60% higher than under the blue LED treatment. However, flower bud initiation was inhibited under red LED treatment, and floral bud formation was then not observed at the end of experiment. The expression of the SOC1-like gene FBP28 in petunia was changed by light quality. Under white fluorescent light and blue LED light the transcript levels of FBP28 showed a diurnal rhythm. The transcript levels increased during the morning, and remained high during the lighting period. On the other hand, the expression of FBP28 was lower under red LED treatment during the lighting period. In Arabidopsis, the expression of SOC1, which is one of the key genes in floral induction, is stimulated by a signal from cryptochrome blue light receptors. In petunia, blue LED light as well as the blue part of the spectrum in white fluorescent light, can also induce FBP28 and floral induction, probably by a signal from cryptochrome-like photoreceptors.

Involvement of aba in flower induction of Pharbitis nil

<p>Flowering of plants is controlled by hormones among which both stimulators and inhibitors are present. The role of abscisic acid (ABA) in flower induction of the short day plant <em>Pharbitis nil</em> was shown in our experiments through exogenous applications and endogenous level determination of the hormone in cotyledons of seedlings grown under special light conditions.</p><p>The application of ABA to cotyledons or shoot apices during the first half of a 24-h long inductive night inhibits flowering. The same compound applied towards the end of or after a 14-h long subinductive night increases the number of flower buds produced by these plants.</p><p>Exposing <em>P. nil</em> seedlings at the beginning of a 24-h long inductive night to far red light (FR) decreases the level of endogenous abscisic acid in cotyledons and leads to flower inhibition. However, a pulse of red light (R) reversing the inhibitory effect of far red light on the flowering of <em>P. nil</em> increases the ABA content.</p><p>The results obtained confirm previous observations that ABA may play a dual and an important role in the regulation of floral bud formation in <em>P. nil</em>. The flowering occurs when the level of endogenous abscisic acid is low at the beginning and is high toward the end of the inductive night.</p>

FLORAL BUD INITIATION AND DEVELOPMENT OF THREE PEAR TREE (PYRUS SP.) CULTIVARS IN TWO SUBTROPICAL REGIONS DURING THE SUMMER PERIOD

The flower formation in fruit trees is in the spring but actually begins in the previous summer. Flowers are induced in the apex of the buds, which were vegetative previously. After flower induction, which is still an unknown process, successive steps of physiological processes occur and morphological differentiation, when the apex becomes organized into a primordia of flower (or inflorescence). The first morphological change that occurs in the meristem is a 'broadening' of the apex, which also becomes convex, followed by its lengthening into a cylindrical shape and the formation of sepal primordia in the terminal flower (king flower). After this transformation, organ primordia become differentiated laterally. The time of floral bud formation in the fruit trees is of great importance, because it will determine the development level that these buds will reach before beginning the dormancy period, having a decisive effect on the quality of the produced inflorescence. The objective of this work was to investigate the time of floral bud initiation and development in three pear tree cultivars ('Packham's Triumph', 'Abate Fetel' and 'Housui') in two subtropical regions of Rio Grande do Sul state (Pelotas and Vacaria) during the growth period in 2007. To evaluate the floral bud initiation, terminal and axillary buds of long shoots and apical buds of spurs were collected from January 9 th , in a 15-day interval, until march 14 th , fixed in a solution of formalin, acetic acid and alcohol (FAA) and dissected under a stereoscopic microscopy in the Laboratory of Imunology and Electronic Microscopy at Embrapa Clima Temperado, Pelotas-RS. The time of floral bud initiation did not practically differ between the two regions to the three cultivars observed. However, the time of floral bud initiation differed between cultivars and, also, the three cultivars presented a differentiated behavior in the flower bud development. In the beginning of the observations, the spur buds of 'Housui' had already initiated and presented in more advanced stages of floral development than the other two cultivars. The floral initiation in the 'Packham's' spur buds and in the 'Housui' terminal buds occurred in late January. The spur buds of 'Abate Fetel', terminal buds of 'Packham's' and axillary buds of 'Housui' were initiated in early February. In the middle of March, the spurs of 'Housui' and 'Packham's' and the terminal buds of 'Housui' reached the carpel primordia stage.

Identification of a TFL1 ortholog in Japanese apricot ( Prunus mume Sieb. et Zucc.)

PmTFL1, Prunus mume ortholog of TFL1 ( TERMINAL FLOWER 1), was isolated and characterized to investigate the relationship to floral bud formation in Japanese apricot ( P. mume). PmTFL1 consists of a 1251-bp open reading frame (ORF), which encodes 172 amino acid residues, consisting of three introns and four exons. The PmTFL1 sequence shows high identity to Arabidopsis thaliana TFL1 and TFL1 orthologs of other plant species. The transgenic Arabidopsis expressing PmTFL1 under the control of cauliflower mosaic virus 35S promoter produced many rosette leaves and significantly delayed the flowering time. Some of the transgenic plants with higher expression of PmTFL1 took more than 70 days to flowering, showing that PmTFL1 has the same function as the Arabidopsis TFL1 to maintain the vegetative growth and suppress flowering. PmTFL1 transcripts were detected only in leaf buds and young expanding leaves in adult trees and in the leaves, stems, and roots in juvenile seedlings. PmTFL1 was suggested to be involved in the development of juvenile and young vegetative organs.

Early inflorescence and floral development in Cocos nucifera L. (Arecaceae: Arecoideae)

Palms are generally characterized by a large structure with a massive crown that creates difficulties in anatomical studies. The flowering behaviour of palm species may be a useful indicator of phylogenetic relationships and therefore evolutionary events. This paper presents a detailed histological study of reproductive development in coconut ( Cocos nucifera L.), from initiation up to maturation of staminate and pistillate flowers. Reproductive development in coconut consists of a sequence of individual events that span more than two years. Floral morphogenesis is the longest event, taking about one year, while sex determination is a rapid process that occurs within one month. The inflorescence consists of different ultimate floral structural components. Pistillate flowers are borne in floral triads that are flanked by two functional staminate flowers. The staminate flowers are born in floral diads towards the base of the rachilla followed by solitary flowers in the middle to top of the rachilla. Three primary phases were identified in reproductive development, namely, transition of axillary bud into inflorescence bud, formation of floral buds, and sexualisation of individual flower buds. All developmental events with respect to stage or time of occurrence were determined.

RELATIONSHIP BETWEEN FLORAL BUD INDUCTION BY APPLICATION OF KCLO3 AND NITRATE REDUCTASE ACTIVITY OF LEAVES ON LONGAN

Longan (Dimocarpus longan Lour.) trees were treated with potassium chlorate (KClO 3 ) in soil in June. The changes of nitrate reductase activity, C/N and the main nutrient elements in the leaves were determined in a period of floral bud formation. Results showed that the trees were induced to form floral bud and bloom 30 days after the trees were treated with KClO 3 . Floral bud differentiation began after the trees were treated for 75 days with both KClO 3 and Padobutrazol (PP 333 ). The content of nitrate reductase in the leaves was reduced on a period of time after treatment began after. It began to increase at the floral physiological phase and reached the peaks at the morphological differentiation, then fell down. The content of nitrate reductase of control (CK) was kept on a lower level. Otherwise, relationship between flower bud formation induced and changes of the content of chlorate in the leaves were undefined.

Identification of an FT ortholog in Japanese apricot (Prunus mume Sieb. et Zucc.)

SummaryPmFT, a Prunus mume ortholog of FT (FLOWERING LOCUS T) in Arabidopsis thaliana (L.) Heynh., was isolated and characterised to elucidate the mechanism of floral bud formation in Japanese apricot (P. mume). The Japanese apricot genome contained a single locus of PmFT. PmFT consisted of a 1,473-bp open reading frame with three introns and four exons, which encoded 174 amino acid residues. The PmFT sequence showed high identity to A. thaliana FT and to FT orthologs in other plant species. Wild-type and ft-1 strains of Arabidopsis that were transformed with 35S:PmFT showed precocious flowering, indicating that PmFT has the same function as A. thaliana FT and FT orthologs in other plant species. PmFT transcripts were found in all tissues examined, with more abundant expression observed in tissues from adult trees than from seedlings.

Plant Regeneration and Floral Bud Formation from Intact Floral Parts of African Violet (Saintpaulia ionantha H. Wendl.) Cultured in vitro

Intact immature flower buds of African violet (Saintpaulia ionantha H. Wendl.) were used as explant sources for in vitro studies. The effect of exogenous hormones, NAA and BAP on the indirect organogenesis of this species was observed. Callus was formed on the cut end (base) of pedicels of floral buds where they were in contact with the medium. When maintained on the same medium, callus was differentiated into adventitious shoots after 10 weeks in culture. MS media supplemented with 2.0 mg L(-1) NAA and 1.0 mg L(-1) BAP gave the highest number of sterile or vegetative floral buds from the surface of callus of the explants, but these buds failed to develop further. The floral buds were expanded as abnormal flowers. The floral structures were smaller in size compared to intact flowers. Petals (corolla) were white to purple in colour but did not form any reproductive organs, i.e., stamens or pistils. All sterile or vegetative floral buds and abnormal flowers survived for 3 months in culture but failed to reach anthesis.

(263) Temperature Effects on Meristem Identity Genes Controlling the Reproductive Development of Cauliflower (Brassica oleracea var. botrytis) and Broccoli (Brassica oleracea var. italica)

Brassica oleracea species differ in the developmental stage of their reproductive meristems at harvest. The stage that characterizes each variety depends on its genetic makeup, environment and the interaction between them. We tested a model of arrest in B. oleracea to determine functional redundancy among the paralogous genes CAL, AP1a, AP1c, FULa, FULb, FULc, and FULd; and to resolve the immediate effect of temperature on gene expression in meristems whose developmental fate is temperature regulated. By varying temperature during reproductive development, three stages of arrest were obtained: inflorescence meristem (cauliflower), floral meristem (intermediate) and floral bud (broccoli), the latter initiated by low temperature. Gene expression was measured by quantitative real time PCR (qRT-PCR). The LFY/TFL1 ratio increased as the reproductive development advanced, mainly due to decreased TFL1 expression; influenced by a dramatic increase in AP1c toward floral bud formation. The expression patterns of the FUL paralogs indicate different roles in reproductive development. FULa was more abundant in the floral primordia, while FULb, FULc, and FULd were associated with earlier arrest at the inflorescence meristem stage. The high expression of FULc and FULd at all stages of arrest differs from their homolog in Arabidopsis. High temperature reduced AP1 and LFY expression but the meristem did not revert from reproductive to vegetative. Floral bud formation in plants recessive for AP1a and CAL reaffirm that functional redundancy among some of these genes can complement the mutations. Varying temperature alone, at a fixed developmental stage, caused little variation in the expression of genes studied, causing small significant differences in TFL1 and AP1c.

The Effect of Interrupting Short Day Cycles with Day-length Extension on Floral Bud Initiation in Strawberry (Fragaria × ananasa)

Experiments were conducted to investigate the potential effect on floral bud initiation in strawberry (Fragaria × ananasa, cv. Chandler) by interrupting inductive short day cycles with a day-length extension treatment. Vegetative plants were exposed to 10-, 15-, or 20-day cycles of inductive short days in growth chambers. After receiving an inductive short day treatment plants were transferred to a greenhouse where they were exposed to non-inductive long days, which stimulated panicle elongation. Dissections of apical meristems immediately following each cycle of short days revealed that cycles of 20 days resulted in detectable floral bud formation. After 15 days in the greenhouse, all short day treatments had initiated floral buds. In the greenhouse, under long days, subsequent flowering in cohorts of plants which had previously received inductive short days showed a positive correlation between interruption of short days with day length extension and reduction in the number of floral buds initiated on earliest emerging panicles. These results suggest potential for manipulation of floral bud induction and potentially fruit size in Chandler, and perhaps other cultivars by interruption of a cycle of inductive short days with a day length extension treatment.

Inhibitory Effect of Methyl Jasmonate on Flowering and Elongation Growth in Pharbitis nil

The effect of methyl jasmonate (JA-Me) on the floral bud formation and elongation growth in the short-day plant Pharbitis nil was investigated. The placing of 4-day-old seedlings of P. nil in a solution of JA-Me for a period of 24 h before an inductive (16 h or 14 h of darkness) night led to a dramatic reduction in the number of flower buds formed by the plant. Plants treated with JA-Me also totally lost their capacity to form a generative terminal bud. JA-Me applied after photoinduction does not inhibit flowering. Gibberellic acid (GA3) partly reverses the inhibitory effect of JA-Me. Plants treated simultaneously with JA-Me and GA3 formed about 3 flower buds more than plants treated with JA-Me only. JA-Me at a concentration of 10-7 M stimulates slightly, but at higher concentrations it inhibits root growth and shoot growth. A distinct lack of correlation between the effect of JA-Me on inhibition of flowering and shoot and root growth was noted. This indicates the independent action of JA-Me in controlling both processes.

Induction of early bolting in Arabidopsis thaliana by triacontanol, cerium and lanthanum is correlated with increased endogenous concentration of isopentenyl adenosine (iPAdos).

The effects of triacontanol (TRIA), applied singly or in combination with cerium nitrate and lanthanum nitrate, on bolting of Arabidopsis thaliana were studied. Triacontanol (0.1 to 0.6 microM) added to the culture medium induced early bolting. TRIA (0.3 microM) applied with low concentrations of cerium and lanthanum caused a synergistic stimulation of bolting. In medium containing 0.3 microM TRIA, 0.1 microM cerium nitrate and 0.1 mM lanthanum nitrate, 82% of the plants bolted 20 d after seed sowing compared to only 8.6% in basal medium and 47.8% in medium with TRIA only. The changes in the endogenous concentrations of total cytokinins of the isopentenyl adenine (IP) subfamily in the leaf and root tissues were correlated with TRIA-induced early bolting. The combined treatment of TRIA (0.3 microM), cerium nitrate (0.1 microM) and lanthanum nitrate (0.1 mM) resulted in a significant increase in the endogenous concentrations of total cytokinins of the IP subfamily in the root and leaf tissues compared to plants growing in the basal medium and medium with TRIA. The exogenous application of six natural cytokinins to the plants revealed that only isopentenyl adenosine (iPAdos) was as effective as TRIA on floral bud formation. iPAdos was also found to have similar effects as TRIA on root growth and reproductive growth. These results suggest a correlation between the early bolting induced by TRIA, cerium and lanthanum and the production of higher concentrations of endogenous iPAdos.

Expression Pattern of Homologues of Floral Meristem Identity Genes LFY and AP1 during Flower Development in Apple

Two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] homologous fragments of FLO/LFY and SQUA/AP1 (AFL and MdAP1, respectively) were analyzed to determine the relationship between floral bud formation and floral gene expression in `Jonathan' apple. The AFL gene was expressed in reproductive and vegetative organs. By contrast, the MdAP1 gene, identified as MdMADS5, which is classified into the AP1 group, was expressed specifically in sepals concurrent with sepal formation. Based on these results, AFL may be involved in floral induction to a greater degree than MdAP1 since AFL transcription increased ≈2 months earlier than MdAP1. Characterization of AFL and MdAP1 should advance the understanding of the processes of floral initiation and flower development in woody plants, especially in fruit trees like apple.

Polyaxial development in homeotic flowers of three begonia cultivars

Development of staminate flowers in double-flowering Begonia semperflorens-cultorum cultivars 'Cinderella', 'Goldie Locks', and 'Lucy Lockett' was examined using epi-illumination microscopy, focussing on later stages when secondary partial floral buds formed on the floral apex. This process, switching from floral to inflorescence-like development, is an example of homeosis, the expression of inflorescence features on a floral apex. Floral development began as in a normal begonia flower with the formation of a perianth consisting of two sepals and two petals, but sepaloid and (or) petaloid appendages then developed in what corresponded to stamen positions in normal Begonia species. This was usually followed by lateral elongation, distortion of the primary floral apex, and formation of secondary partial floral buds. The pattern of primordial inception on the secondary apices tended to be irregular, but in some cases, appendage primordia formed in groups of twos, threes, and fours, and in a somewhat alternating formation on the apices. Often, primordial initiation seemed to continue on secondary apices even after anthesis of the staminate flower. Appendage primordia that formed on the secondary buds usually were laterally elongate and bifacial, giving them a phyllomic appearance. Others were, on occasion, more hemispherical at inception, but as they developed they became phyllomic. Key words: homeosis, polyaxial, floral development, intermediate inflorescence.

Difluoromethylornithine counteracts effects of auxins and inhibitors of polar auxin transport on plant development

Difluoromethylornithine (DFMO) counteracted several processes that are promoted or inhibited by auxins or inhibitors of polar auxin transport: inhibition of asymmetric gene expression in carrot, stimulation of gametic embryogenesis inBrassica, inhibition of root elongation in tobacco, inhibition of the development of lateral roots in pea and adventitious roots in apple, and inhibition of floral bud formation inArabidopsis

Floral induction and development in Phalaenopsis in vitro

Adventitious shoots formed from nodal sections of floral-stalks of Phalaenopsis Pink Leopard ‘Petra’ that had been propagated on Hyponex medium with 6-benzyladenine (BA). After subculturing adventitious shoots on Vacin-Went medium with BA, more than 70% of the shoots formed floral buds, and 10% of the floral buds flowered in 9-month-old shoots. Floral buds were not formed on the adventitious shoots cultured on Vacin-Went medium lacking BA. A high concentration of total nitrogen inhibited the development of floral buds, and low-temperature treatments failed to induce the formation of floral buds in vitro.