Floral Bud Formation Research Articles

In vitro floral development in × Doriella Tiny ( Doritis pulcherrima × Kingiella philippinensis)

Flowering was induced in 7-month-old × Doriella Tiny ( Doritis pulcherrima × Kingiella philippinensis) explants in an vitro system. The system consists of vegetative bud propagation by 6-benzyladenine (BA) in a Hyponex medium, initiation of floral buds by BA in a Vacin Went medium and floral development in a BA-free Hyponex medium. BA was required for the formation of floral buds on explants under certain nutritional conditions, including the appropriate content of sucrose and nitrogen in the culture media. Use of kinetin, 2iP or coconut water in Vacin Went medium was ineffective in the induction of floral buds. Floral buds developed in the presence of both BA and sucrose in the Vacin Went and MS ( 1 10 ) media, while almost no floral buds formed in the Hyponex medium, even with BA and sucrose. A relatively larger number of vegetative buds were produced in the Hyponex medium with added BA than in the Vacin Went and MS media with added BA.

Floral gradient in flowering tobacco in relation to free amino acids

By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those from the tobacco plants in full blooming or fruiting stages. Analysis of free amino acid levels revealed the acropetal gradient of Pro in flowering tobacco stem. L-Pro, L-Trp, D,L-Met and L-Arg were respectively added into the culture medium for testing their influence on floral bud formation from tobacco pedicel segments. Only L-Trp evidently enhanced the floral bud neoformation.

Roles of Nitrogen and Carbohydrate in Floral-bud Formation in Pharbitis Apex Cultures

Summary Apex explants from non-induced Pharbitis plants were cultured under non-inductive conditions on various media to investigate the effects of nitrogen and carbohydrate on floral-bud formation. Lowering total-nitrogen concentration or eliminating NH 4 Cl in the culture medium stimulated flower induction. Increasing sucrose concentration was also effective in inducing flowering.

Requirement of the Auxin Polar Transport System in Early Stages of Arabidopsis Floral Bud Formation.

The pin-formed mutant pin 1-1, one of the Arabidopsis flower mutants, has several structural abnormalities in inflorescence axes, flowers, and leaves. In some cases, pin1-1 forms a flower with abnormal structure (wide petals, no stamens, pistil-like structure with no ovules in the ovary) at the top of inflorescence axes. In other cases, no floral buds are formed on the axes. An independently isolated allelic mutant (pin1-2) shows similar phenotypes. These mutant phenotypes are exactly the same in wild-type plants cultured in the presence of chemical compounds known as auxin polar transport inhibitors: 9-hydroxyfluorene-9-carboxylic acid or N-(1-naphthyl)phthalamic acid. We tested the polar transport activity of indole-3-acetic acid and the endogenous amount of free indole-3-acetic acid in the tissue of inflorescence axes of the pin1 mutants and wild type. The polar transport activity in the pin 1-1 mutant and in the pin1-2 mutant was decreased to 14% and 7% of wild type, respectively. These observations strongly suggest that the normal level of polar transport activity in the inflorescence axes is required in early developmental stages of floral bud formation in Arabidopsis and that the primary function of the pin1 gene is auxin polar transport in the inflorescence axis.

Requirement of the Auxin Polar Transport System in Early Stages of Arabidopsis Floral Bud Formation

Requirement of the Auxin Polar Transport System in Early Stages of Arabidopsis Floral Bud Formation

The effects of auxin and antiauxin in an in vitro bioassay of flower regulatory activity in leaf exudate from tobacco plants

An in vitro bioassay system for floral bud formation has been established using Nicotiana tabacum L. cv. MC, explants excised from floral stalks cultured on modified Murashige‐Skoog medium containing excess auxin and antiauxin. Three auxins. indolyl‐3‐acetic acid (IAA), 4‐chloroindolyl‐3‐acetic acid and 5,6‐dichloroindolyl‐3‐acetic acid, were tested for floral bud‐forming activity; IAA was most efficient. Three antiauxins. 5,7‐dichlorindolyl‐3‐isobutyric acid (5,7‐Cl2‐HBA), p‐chlorophenoxyiso butyric acid and 2,3,5‐triiodobenzoic acid, were tested for the ability to reverse the inhibition of floral bud formation caused by excess IAA. Only 5,7‐Cl2‐HBA was very effective. Leaf exudates from short day‐ and long day‐treated tobacco plants were added to the bioassay system which contained 1 µM 6‐benzylaminopurine, 5 µM IAA and 5 µM 5, 7‐Cl2‐HBA, Interestingly, only the leaf exudate from short day‐treated plants stimulated floral bud formation. Moreover, the buds produced grew into large. well‐developed ones with shapes similar to those of the natural floral buds of intact tobacco plants.

Effects of optically active abscisic acid on floral bud formation.

Effects of optically active abscisic acid on floral bud formation.

Growth and development of Brassica genotypes differing in endogenous gibberellin content. I. Leaf and reproductive development

Leaf and reproductive development were compared in 3 rapid cycling Brassica rapa genotypes grown for 4 weeks under greenhouse conditions. The dwarf mutant, rosette (ros), is gibberellin (GA)-deficient, while the tall mutant, elongated internode (ein), has enhanced endogenous GA levels. Germination was delayed in ros and a selection of a more severe form of ros, named dormant (do), has even more retarded germination and some seeds entirely fail to germinate. Seeds of do and ros respond to exogenous GA, by rapid germination. The 3 genotypes, ros, normal and ein, displayed similar developmental sequences, although floral bud formation and subsequent floral development and anthesis were delayed in ros. Conversely, anthesis was slightly accelerated in ein. Individual leaf areas were reduced in both ros and ein relative to the normal genotype, but leaf numbers were similar in all 3 genotypes. Differences in leaf morphology (heterophylly) were also observed; the normal genotype and ein plants possessed uniform leaf shapes and relatively smooth leaf margins, although petiole length was increased in ein. The mutant ros had scalloped leaf margins and convoluted leaf blades in addition to shortened petioles. These phenotypes suggest a role for GA in the regulation of germination and reproductive and leaf development in Brassica.

Function of the apetala-1 gene during Arabidopsis floral development.

We have characterized the floral phenotypes produced by the recessive homeotic apetala 1-1 (ap1-1) mutation in Arabidopsis. Plants homozygous for this mutation display a homeotic conversion of sepsis into brachts and the concomitant formation of floral buds in the axil of each transformed sepal. In addition, these flowers lack petals. We show that the loss of petal phenotype is due to the failure of petal primordia to be initiated. We have also constructed double mutant combinations with ap1 and other mutations affecting floral development. Based on these results, we suggest that the AP1 and the apetala 2 (AP2) genes may encode similar functions that are required to define the pattern of where floral organs arise, as well as for determinate development of the floral meristem. We propose that the AP1 and AP2 gene products act in concert with the product of the agamous (AG) locus to establish a determinate floral meristem, whereas other homeotic gene products are required for cells to differentiate correctly according to their position. These results extend the proposed role of the homeotic genes in floral development and suggest new models for the establishment of floral pattern.

Further experiments on spermidine-mediated floral-bud formation in thin-layer explants of Wisconsin 38 tobacco

We studied the effects of various polyamines on bud regeneration in thin-layer tissue explants of vegetative and floweringNicotiana tabacum L. cv. Wisconsin 38, in which application of exogenous spermidine (Spd) to vegetative cultures causes the initiation and development of some flower buds (Kaur-Sawhney et al. 1988 Planta173, 282). We now show that this effect is dependent on the time and duration of application, Spd being required from the start of the cultures for about three weeks. Neither putrescine nor spermine is effective in the concentration range tested. Spermidine cannot replace kinetin (N(6)-furfurylaminopurine) in cultures at the time of floral bud formation, but once the buds are initiated in the presence of kinetin, addition of Spd to the medium greatly increases the number of floral buds that develop into normal flowers. Addition of Spd to similar cultures derived from young, non-flowering plants did not cause the appearance of floral buds but rather induced a profusion of vegetative buds. These results indicate a morphogenetic role of Spd in bud differentiation.

Suberization and bud formation in tobacco explants

SUMMARYWound‐healing and floral bud formation were studied in explants of Nicotiana tabacum L. Examination of sectioned material by conventional light microscopy, fluorescence microscopy and electron microscopy showed that suberin is formed in cells at the cut surface in close contact with the medium, after 4–7 days of culture.The number of cells depositing suberin depended on the agar concentration in the medium. In explants cultured on a medium with low agar concentration (0‐2 % agar), fewer cells showed suberin deposition and more callus cells without suberin were found. Explants cultured on a medium with high agar concentration (5 % agar) formed a complete layer of cells with suberin deposition.In tobacco explants floral determination occurred within 4 days after explantation. The inability of the explants to form floral buds after this period is probably due to barrier formation by suberin.

Feruloylputrescine and Caffeoylputrescine Are Not Involved in Growth and Floral Bud Formation of Stem Explants from Nicotiana tabacum L. var Xanthi nc

The role of feruloylputrescine (FP) and of caffeoylputrescine (CP) was investigated in an explant system of stem explants from day-neutral Nicotiana tabacum L. var Xanthi nc. Previously, a correlation between cortical callus formation and increase in FP content, as well as between in vitro flower formation and increase in CP content had been shown. During the explant growth in vitro, the increase of both FP and CP was inhibited by 4-fluor-(1-amino-2-phenylethyl)phosphonic acid and 2-amino-indene-2-phosphonic acid, both inhibitors of phenylalanine ammonia-lyase (EC 4.3.1.5). dl-alpha-difluoromethylarginine, an inhibitor of arginine decarboxylase (ADC, EC 4.1.1.19), prevented only the increase in FP, while dl-alpha-difluoromethylornithine, an inhibitor of ornithine decarboxylase (EC 4.1.1.17), reduced only that of CP. Increase in dry weight and the formation of cortical callus and of floral buds of explants were not affected by any of the inhibitors. We conclude, in contrast to earlier hypotheses, that FP and CP do not trigger growth and differentiation in the explants. It seems more likely that FP and CP increase in response to auxin and cytokinin in the media.

Regulatory actions of optically active abscisic acid on floral bud formation and timing of flowering in several plants.

Regulatory actions of optically active abscisic acid on floral bud formation and timing of flowering in several plants.

Flower production, male sterility and berry setting in andigena potato

Unlike tuberosum, andigena potato germ plasm exhibits a high degree of genetic variation in morphological, biochemical and reproductive traits. Sixty-five percent of the 565 genotypes comprising 145 accessions of Solanum tuberosum ssp. andigena obtained from Argentina, Bolivia, Chile, Colombia and Peru remain totally vegetative and never develop any floral bud when cultivated in northern India. In 18% of genotypes, the floral buds develop but they drop off from the plants prematurely. Thus, 83% of genotypes do not develop mature flowers. The frequency of such genotypes is maximum in the Bolivian genotypes. Whereas 17% of genotypes produce mature flowers, only 2% develop berries. The highest proportion of floral bud formation and their subsequent development and differentiation into mature flowers occur in Peruvian and Colombian genotypes. Partial to high male sterility occurs in 93% of the flowering genotypes; their pollen sterility ranges from 15% to 91%. Seven percent of the flowering genotypes are completely pollen sterile. The male sterility is expressed variously, ranging from structural to sporogenous types. The floral bud formation, its development and retention to maturity, pollen and ovule functionability and fruit development are under the control of a large number of genes, most of which are unlinked and independent. Many of these genes are polygenic in nature.

Free and conjugated polyamines during de novo floral and vegetative bud formation in thin cell layers of tobacco

The concentrations of three classes of polyamines, trichloroacetic acid‐soluble (free), TCA‐soluble conjugated (to small molecules) and TCA‐insoluble conjugated (to macromolecules), was examined during de novo floral and vegetative bud formation in thin cell layers of Nicotiana tabacum L. cv. Samsun. Explants (consisting of 5–6 layers of epidermal, subepidermal and parenchyma cells) were excised either from floral pedicels or from stem internodes at the unripe fruit stage and cultured on the same medium. In the former, the first de novo formed flower buds appeared on day 8 of culture, while in the latter the first vegetative domes appeared on day 10. In both cases the number of floral and vegetative buds increased up to day 12 and 15, respectively. Changes in dry weight were determined throughout the culture period. Free and conjugated putrescine titer increased 5–60 times in both types of culture and in the three classes of polyamines examined; spermidine content also increased, while spermine, when present, did not show significant changes. TCA‐soluble conjugated polyamines were most abundant, being about 2‐fold the TCA‐insoluble conjugated ones and 10‐fold the free ones. The major increment in putrescine and spermidine content occurred in stem internode explants developing vegetative buds. In pedicel explants the maximum putrescine level was reached before or on day 8 in culture (emergence of the first flower buds with calyx initials), while in stem internode explants the maximum level was reached on day 12, at the emergence of the first vegetative buds with leaf primordia. While spermidine prevailed on day 0, putrescine was the most abundant polyamine during both differentiation processes. The putrescine content rapidly increased immediately after the onset of culture. Thus conjugated polyamines, especially putrescine, and not only the free ones, seem to be involved in both the reproductive and vegetative phases of tobacco growth and development.

Histochemical study of vegetative and floral bud formation in tobacco stem expiants

Primary explants from the inflorescence stem of tobacco and primary explants from the stem of vegetative plants, cultivatedin vitro under the same conditions, display different morphogenetic ability. The former give rise mostly to floral buds, whereas the latter exclusively to vegetative ones. Histological and histochemical analyses of both original andin vitro cultivated explants were made. They showed differences in chlorophyll content and alcohol dehydrogenase (AD) activity of the original explants reflecting their different metabolic status. Bud primordia were initiated in the superficial meristematic layer derived from epidermal tissues. Floral or prefloral apices were characterized by a strong AD activity in all cells of the meristem, while in vegetative apices AD activity was restricted to their uppermost parts. A high rate of procambium differentiation connected with leaf primordia formation was typical of vegetative buds. A higher concentration of glucose (5 %) enhanced cell division in explants, which is also correlated with a higher AD activity. The significance of vascular tissues for differentiation of vegetative buds is discussed.

ORIGIN AND DEVELOPMENT OF FLORAL BUDS IN TOBACCO EXPLANTS.

Initiation and formation of floral buds was studied on explants of Nicotiana tabacum. During the first stage of development (0 to 4 d), protrusions are formed at the basal side of the explant as a result of cell divisions in both sub-epidermal and epidermal cell layers. The second stage (4 to 7 d) is characterized by the formation of tracheary centres inside the protrusions followed by the formation of floral primordia at the surface of the protrusions. These primordia result from both epidermal and sub-epidermal cell divisions. In the final stage (7 to 15 d), flower primordia develop into flower buds and tracheary elements grow into the buds. Polarity present in cells of freshly cut explants is lost within a few days after the onset of the experiment. After 4 to 7 d, a new polarity axis has differentiated inside the protrusion. This axis runs from the tracheary structure inside the protrusion to the flower primordium at the periphery.

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.

Systematics of Isocarpha (Compositae: Eupatorieae)

Isocarpha comprises five species ranging from southern Texas and the Bahamas to northern Peru and northeastern Brazil. The genus belongs in Eupato­ rieae rather than Heliantheae, but structure of the head of Isocarpha with its elon­ gate, chaffy receptacle is anomalous within Eupatorieae. An hypothesis is presented suggesting the evolutionary derivation of this type of head through formation of floral buds in the axils of the involucral bracts. Generic ties of Isocarpha within Eupatorieae are unclear, but the closest affinities appear to be with Ayapana and relatives. Isocarpha is a small g~nus of Latin American Compositae occurring principally within Mexico, Central America, the Caribbean, and northern South America. Taxonomic problems at the specific and varietal levels have persisted for many years, but more vexing have been questions of generic, subtribal, and tribal affinities. Isocarpha has been treated as be­ longing both to Eupatorieae (Robinson and King 1977) and Heliantheae (Stuessy 1977). Part of this difficulty of tribal placement has derived from the unusual conical receptacle and lack of differentiation between in­ volucral and receptacular bracts. These problems suggested the need for' a modern revision with focus on reproductive morphology and tribal and generic affinities. TAXONOMIC HISTORY Isocarpha was first recognized by Robert Brown (1817) who formed the genus to accommodate two Linnaean species, Galea opPositifolia and Spi­ lanthus atriplicifolius, that were discordant elements in the genera to which they had originally been assigned. Cassini (1822, 1823) suggested that Isocarpha be placed in Heliantheae and added two additional species (I. kunthii and I. pyrethraria), both of which we have excluded from the genus. i.Lessing (1830), believing Brown's Isocarpha to be congeneric with Gal- ydermos Lagasca (=Galea L., Heliantheae), described as new his own ver­ sion of Isocarpha in which he included a new species, I. echioides. This taxon was later transferred by Hemsley (1881) to Ageratum (Eupatorieae). In 1831, Lessing reversed his opinion and merged his own version of Isocarpha with that of Brown and added to it another new spe~ies (I. billbergiana). In the same publication (Lessing 1831) he noted that species

Influences of Environmental and Physiological Conditions on Floral Bud Formation of Torenia Stem Segments Cultured in vitro

Internodal segments of Torenia fournieri Lind. differentiated floral buds when they were grown on a defined nutrient medium lacking NH 4 NO 3 . Two environmental factors, temperature and light, strongly affected floral bud formation. A temperature of 25 ± 2 °C, 8 hr short day photoperiod, and a light intensity of 5000 lux gave the best flowering response. Physiological factors such as the size of explants, the age of mother plants and the stem portions from which explants were taken, also influenced floral bud formation. The highest percentage of floral bud formation was obtained with 4 mm long explants prepared from the 2nd stem internodes of 12 week old plants, of which 91% of cultures produced floral buds.