Stages Of Floral Development Research Articles

Association between floral bud size and developmental stage in soybean microspores

This study was carried out to establish the association between floral bud size and the corresponding microspore developmental stages for Brazilian soybean cultivars. Microspore developmental stage distributions were examined in young buds from cv Década, IAS5 and RS7. The data indicated that for a given bud-size group, the microspores of different cultivars were at different developmental stages, with cv RS7 and Década distributed at the youngest and cv IAS5 at the most advanced stages. Microspore stages distribution were also compared among the ten anthers of the same bud of the above cultivars. The ten anthers from a given bud were clearly distributed at different developmental stages. Caution should be exercised when adopting the standard anther culture practice of using the microspore stage of one anther to represent the entire bud.

Floral morphology and anatomy of Pittosporum tobira (Pittosporaceae)

Comparative studies are made on floral morphology and anatomy of female and male flowers of Pittosporum tobira. The two types of flower differ little from each other in structure at the early stage of floral development, but appear dimorphic towards anthesis. The male flower becomes cryptically bisexual, although its pistil is slender compared to that of the female flower. The stigmas of the male flower are receptive and can induce pollen germination. The structure of the style in the male flower is identical to that in the female flower. Ovules are produced on the protruded parietal placenta in the male flower, but their development is arrested at the stage of the 4–nucleate embryo sac. The female flower is clearly unisexual, with obviously aborted and sagittate anthers. Its pistil is rather plump and can produce darkish red seeds immersed in sticky pulp. The male and female flowers are similar in vascular anatomy. A conspicuous difference between the two types of flower lies in the stamens. Variation of sexual organs in the genus Pittosporum is reviewed. We assume that the flowers of Pittosporum are derived from the hermaphrodite‐flowered ancestor and the female flower has become unisexual through partial reduction of sexual organs at a faster rate than the male flower.

Isolation and characterization of two homeodomain leucine zipper genes from the dioecious plant Silene latifolia.

Homeodomain leucine zipper (HD-Zip) genes encode transcription factors that are characterized by both a homeodomain and a leucine zipper motif. Two HD-Zip genes were isolated from cDNA of the male flower bud of the dioecious plant Silene latifolia. The two isolated genes, SlHDL1 and SlHDL2, encode proteins with the characteristics of HD-Zip transcription factors belonging to HD-Zip classes I and II, respectively. The expression patterns of SlHDL1 and SlHDL2 throughout the floral developmental stages were studied using real-time PCR and in situ hybridization. SlHDL1 is specifically expressed in the outermost layer of the anthers and gynoeciums with a patchy pattern in the inner layers, suggesting that the product of SlHDL1 plays a role in the early developmental stage of the epidermal tissues of these floral organs. Its expression pattern in the anthers and gynoeciums suggests an involvement in differentiation of the reproductive organs. On the other hand, real-time PCR revealed accumulation of SlHDL2 transcripts in the anther and pollen grains of the male flower. These results suggest that SlHDL1 and SlHDL2 regulate specific targets in restricted regions leading to floral organ differentiation in S. latifolia.

PANSY FLORAL DEVELOPMENT AND NUTRIENT ABSORPTION AS INFLUENCED BY TEMPERATURE, NITROGEN FORM, AND STAGE OF PLANT DEVELOPMENT

Production temperatures can affect the marketability of pansies (Viola × wittrockiana Gams.) by influencing plant growth, the presence of nutrient disorders, and the rate of floral development. The choice of nitrogen (N) form in fertility can also influence pansy growth and nutrition, but the effect of fertility on pansy flowering is not clear. Whether or not temperature and N fertility work together to influence nutrient absorption at different stages of the pansy life cycle is unknown. Our objectives were to determine the influence of temperature and N form on pansy floral development, and to identify the peak nutrient demand periods at different temperatures and ratios of NO3 − to NH4 + in fertility. Pansies cv. ‘Crown White’ were grown in nutrient solution cultures until lateral branches had open flowers. Treatments consisted of two temperatures (12°C and 22°C) and three stages of floral development (five true leaf stage until visible bud, visible bud until first flower, first flower until flowering on lateral branches), and three NO3 − :NH4 + molar % ratios (100:0, 62:38, 25:75) with a total concentration of 100 mg N L−1. A modified Hoagland's solution was used with NO3 −−N supplied as Ca(NO3)2 and KNO3 and with NH4 +−N as (NH4)2SO4. The effects of temperature and N form on the time required for development of different floral stages were assessed. In addition, the influence temperature and N form on nutrient absorption was determined for three pre‐determined stages of floral development to identify peak nutrient demand periods. The timing of flower bud development and first flower was not influenced by treatments. At 22°C, pansies flowered earlier on lateral branches than at 12°C, but these plants also suffered a loss in quality due to unfavorable growth characteristics and the development of nutritional disorders. Individual absorption of plant nutrients at different stages of development varied with temperature and N regime. Overall, pansies absorbed the greatest quantity of magnesium (Mg) before flower bud development, calcium (Ca) after flower bud development, and NH4 +, NO3 − phosphorus (P), and potassium (K) after anthesis. In addition, pansies absorbed more NO3 −, Ca, Mg, and P at 12°C than at 22°C. At times, the absorption of NO3 − was dramatically decreased with increasing NH4 + in solutions. Results suggest that nutrient absorption by pansy in different stages of development is influenced by production temperatures and the choice of N form in fertilization. Adjusting fertility programs according to peak demand periods and production temperatures will help prevent periodic nutrient disorders during the life cycle, and may reduce fertilization costs.

Colonization of an island volcano, Long Island, Papua New Guinea, and an emergent island, Motmot, in its caldera lake. III. Colonization by birds

Abstract Location, Aim Long Island, 55 km north of New Guinea, erupted explosively in the seventeenth century and has been recolonized by animals and plants. Effectively in 1968, an island, Motmot, emerged from Long's 13 km‐diameter fresh‐water caldera lake, about 4 km from the nearest shore. A nested pair of colonization sequences is thus available for study. Long Island has been recolonized by birds, and Motmot has been colonized, presumably from the surrounding ring of Long Island. In order to monitor further colonization of Long Island following bird surveys in 1933 and 1972, and to survey the birds of Motmot, Motmot and the western parts of Long were visited for 15 days in 1999. Results In the last 66 years one species probably has become extinct; in the past 27 years three species have colonized and three, present in 1972, were not recorded in 1999. We assess the present number of nonmigrant land bird species as fifty. On Motmot, we recorded eight species, three breeding, and found two more only as prey remains (three raptor species were seen on the island). Main conclusions Long Island's avifauna still has youthful features. Species with good colonizing ability predominate, and there are no island‐endemic subspecies. There is a persistently high proportion of supertramps; none of the ten supertramps has been replaced by later‐colonizing ‘high‐S' species. A quasi‐equilibrium of about fifty species, fourteen fewer than the predicted equilibrium number for the island, has persisted for at least seven decades and may be seen as that appropriate to the present prolonged stage of Long's floral and vegetational development. Compared with the younger avifauna of Krakatau, Long's avifauna has a higher proportion of nectarivores, predators of large invertebrates and small vertebrates, and ground‐foraging insectivore‐herbivores, and a lower proportion of the insectivore‐frugivore guild. Motmot's small avifauna consists predominantly of species obtaining subsistence from outside the island.

A Molecular Link between Stem Cell Regulation and Floral Patterning in Arabidopsis

The homeotic gene AGAMOUS (AG) has dual roles in specifying organ fate and limiting stem cell proliferation in Arabidopsis flowers. We show that the floral identity protein LEAFY (LFY), a transcription factor expressed throughout the flower, cooperates with the homeodomain protein WUSCHEL (WUS) to activate AG in the center of flowers. WUS was previously identified because of its role in maintaining stem cell populations in both shoot and floral meristems. The unsuspected additional role of WUS in regulating floral homeotic gene expression supports the hypothesis that floral patterning uses a general meristem patterning system that was present before flowers evolved. We also show that AG represses WUS at later stages of floral development, thus creating a negative feedback loop that is required for the determinate growth of floral meristems.

Female meiosis in wild-type Arabidopsis thaliana and in two meiotic mutants

Female meiosis in Arabidopsis has been analysed cytogenetically using an adaptation of a technique previously applied to male meiosis. Meiotic progression was closely correlated with stages of floral development, including the length and morphology of the gynoecium. Meiosis in embryo sac mother cells (EMCs) occurs later in development than male meiosis, in gynoecia that range in size between 0.3 and 0.8 mm. The earliest stages in EMCs coincide with the second division to tetrad stages in pollen mother cells. However, the details of meiotic chromosome behaviour in EMCs correspond closely to the observations we have previously made in male meiosis. In addition, BrdU labelling coupled with an immunolocalisation detection system was used to mark the S phase in cells preceding their entry into prophase I. These techniques allow female meiotic stages of Arabidopsis to be analysed in detail, from the S-phase through to the tetrad stage, and are shown to be equally applicable to the analysis of female meiosis in meiotic mutants.

Influence of high temperature during pre- and post-anthesis stages of floral development on fruit-set and pollen germination in peanut

Peanut (Arachis hypogaea L.) crops are often exposed to day temperatures > 35°C for short periods duringflowering, resulting in lower yields. Research was conducted to study and quantify the effects of short episodes (1– 6 d) of high temperatures during the pre- and post-anthesis stages of floral development on fruit-set, pollen viability, germination and tube growth. Plants of peanut cv. ICGV-86015 were grown in controlled environments at 28/22°C (day/night). High daytime air temperature treatments ranging from 28 (control) to 48°C were imposed at different times between 6 d before anthesis (DBA) and 6 d after anthesis (DAA) for 1, 3 or 6 d. Floral buds or flowers were tagged at different stages to determine fruit-set. Exposure to bud (tissue) temperature ≥ 39°C for 1 d significantly reduced fruit-set compared to the control at 28°C, and the magnitude of the reduction varied with stage of floral development. Floral buds were most sensitive to high temperature at 4 DBA and at anthesis, coinciding with micro-sporogenesis and pollination or fertilisation, respectively. The critical bud temperature at these stages was 33°C, above which fruit-set was reduced by 6% °C –1 . Lower fruit-set due to high temperatures at pre-anthesis and anthesis stages were due to pollen sterility and retarded pollen tube growth, respectively.

Molecular cloning and characterization of cDNA encoding cardosin B, an aspartic proteinase accumulating extracellularly in the transmitting tissue of Cynara cardunculus L.

Cardosins A and B are related aspartic proteinases from the pistils of Cynara cardunculus L., whose milk-clotting activity has been exploited for the manufacture of cheese. Here we report the cloning of cardosin B cDNA and its organ, tissue and cytological localization. The cDNA-derived amino acid sequence has 73% similarity with that of cardosin A and displays several distinguishing features. Cardosin B mRNA was detected in young inflorescences but not in pistils of fully opened inflorescences, indicating that its expression is developmentally regulated. The proteinase, however, accumulates in the pistil until the later stages of floral development. Immunocytochemistry with a monospecific antibody localized cardosin B to the cell wall and extracellular matrix of the floral transmitting tissue. The location of cardosin B in the pistil is therefore clearly different from that of cardosin A, which was found at protein storage vacuoles of the stigmatic papillae and has been suggested to be involved in RGD-mediated proteolytic mechanisms. In view of these results the possible functions of cardosin B in the transmitting tissue are discussed.

Sexual development and sex chromosomes in hop.

The stages of floral development in staminate and pistillate plants of hop (Humulus lupulus) were defined using scanning electron microscopy and light microscopy. Vegetative meristems of male and female plants are morphologically indistinguishable. On transition to the reproductive phase, inflorescence apices reduce greatly in size and striking developmental sex differences become apparent. The first sex-specific differences occur extremely early in floral ontogeny. Both male and female plants initiate inflorescence meristems at each leaf node, each meristem being enclosed within a bract. Male secondary inflorescence meristems give rise to clusters of asynchronously developing flowers. Female inflorescence meristems produce flowers arranged in 'cones'. Each male floral meristem initiates a whorl of five sepal primordia, followed by an inner whorl of five stamen primordia. There is no sign of carpel development at any stage. In females, two carpel primordia are initiated, surrounded at their base by a vestigial perianth whorl. No stamen development is observed. Several monoecious lines carry bisexual flowers, either within cymose panicles or within the basal bracts of terminal female inflorescences. Bisexual flowers usually possess perianth, stamen and carpel whorls. The central whorls are often highly variable, and range from a pair of stigmas fused to a thin central filament to a well developed gynoecium. Chimaeric central whorls consisting of fused staminoid-carpelloid structures also occur. Sex differences in unisexual hop flowers are determined at an extremely early stage in ontogeny. The inappropriate set of sex organs is suppressed before it becomes visible or, more probably, it is not initiated at all. Genes directing the development of sex are likely to act at an extremely early stage, well in advance of floral organogenesis. The sex chromosomes of dioecious hop plants are described, as well as the chromosome constitutions of monoecious plants and those carrying bisexual flowers.

Endothermy by flowers of Rhizanthes lowii (Rafflesiaceae).

Rhizanthes lowii (Beccari) Harms (Rafflesia- ceae) is a parasitic plant that grows in the understory of the rainforest in South-East Asia. This plant does not have leaves, stems, or photosynthetic tissue and is characterised by the emission of a strong odour that attracts the natural pollinators, carrion flies. Flowers that volatilise odorous compounds and attract carrion flies, beetles and other insects are often thermogenic. Here we present evidence of both thermogenesis and thermoregulation in R. lowii from microclimate and tissue temperatures measured during different stages of flower development in R. lowii, in natural conditions in Brunei, Borneo. Endothermy was detected in young and mature buds as well as in blooming flowers and even in decaying tissues 3 or more days after blooming. Tissue temperatures were maintained at 7-9 K above air temperature, in both female and male flowers, at all stages of floral development.

The arabidopsis DELAYED DEHISCENCE1 gene encodes an enzyme in the jasmonic acid synthesis pathway.

delayed dehiscence1 is an Arabidopsis T-DNA mutant in which anthers release pollen grains too late for pollination to occur. The delayed dehiscence1 defect is caused by a delay in the stomium degeneration program. The gene disrupted in delayed dehiscence1 encodes 12-oxophytodienoate reductase, an enzyme in the jasmonic acid biosynthesis pathway. We rescued the mutant phenotype by exogenous application of jasmonic acid and obtained seed set from previously male-sterile plants. In situ hybridization studies showed that during the early stages of floral development, DELAYED DEHISCENCE1 mRNA accumulated within all floral organs. Later, DELAYED DEHISCENCE1 mRNA accumulated specifically within the pistil, petals, and stamen filaments. DELAYED DEHISCENCE1 mRNA was not detected in the stomium and septum cells of the anther that are involved in pollen release. The T-DNA insertion in delayed dehiscence1 eliminated both DELAYED DEHISCENCE1 mRNA accumulation and 12-oxophytodienoate reductase activity. These experiments suggest that jasmonic acid signaling plays a role in controlling the time of anther dehiscence within the flower.

Regulation of cell proliferation patterns by homeotic genes during Arabidopsis floral development.

The shoot apical meristem of Arabidopsis thaliana consists of three cell layers that proliferate to give rise to the aerial organs of the plant. By labeling cells in each layer using an Ac-based transposable element system, we mapped their contributions to the floral organs, as well as determined the degree of plasticity in this developmental process. We found that each cell layer proliferates to give rise to predictable derivatives: the L1 contributes to the epidermis, the stigma, part of the transmitting tract and the integument of the ovules, while the L2 and L3 contribute, to different degrees, to the mesophyll and other internal tissues. In order to test the roles of the floral homeotic genes in regulating these patterns of cell proliferation, we carried out similar clonal analyses in apetala3-3 and agamous-1 mutant plants. Our results suggest that cell division patterns are regulated differently at different stages of floral development. In early floral stages, the pattern of cell divisions is dependent on position in the floral meristem, and not on future organ identity. Later, during organogenesis, the layer contributions to the organs are controlled by the homeotic genes. We also show that AGAMOUS is required to maintain the layered structure of the meristem prior to organ initiation, as well as having a non-autonomous role in the regulation of the layer contributions to the petals.

Morphological characterization of modified flower morphology of three novel alloplasmic male sterile carrot sources

AbstractThree novel sources of cytoplasmic male sterility (CMS) in carrot are characterized by altered flower phenotypes. Flowers were classified into subtypes, according to stamen (and petal) modification. Flower anatomy was investigated by light microscopy to describe organ modification and to specify the timing when morphology begins to deviate. Early stages of floral development were defined in fertile male flowers of the cultivated carrot according to model plants such as Antirrhinum and Arabidopsis and compared with corresponding stages of the novel cytoplasmic male‐sterile flower types. Early organogenesis was identical in the different CMS types and comparable to corresponding stages of unmodified flowers. The morphology of stamens, and in some cases petals, became different in CMS flowers during early organ differentiation. For each CMS type, the cytoplasm appears to influence organogenesis in a specific way. Although homoeosis is usually considered to be controlled exclusively by specific nuclear genes, a role of cytoplasmic factors is suggested

Changes in cytokinin activities before, during and after floral initiation in Polianthes tuberosa

The contents of endogenous cytokinin in tuberose corms ( Polianthes tuberosa) at vegetative, early floral initiation, and flower development stages were investigated. We also determined the influence of exogenous cytokinin treatment on the corm apex at three different growth stages in relation to floral initiation and development in tuberose. The exogenous cytokinin effectively induced floral initiation and development, especially at the early floral initiation and flower development stages. Endogenous cytokinins were higher in early floral initiation and development stages in comparison to the vegetative stage. During floral initiation stage, the zeatin and dihydrozeatin increased significantly, while the cytokinins, zeatin riboside, dihydrozeatin riboside, 6N- ( δ 2 -isopentenyl) adenine, and 6N -( δ 2 -isopentenyl) adenine riboside at consistently low levels. The increase of cytokinin levels in tuberose corms during floral induction suggests a role for cytokinins in tuberose apex evocation. Moreover, these results indicate that cytokinins seem to promote the development of flower buds rather than inducing flowering in tuberose.

Low-temperature Tolerance of Blackcurrant Flowers

The low-temperature tolerance of flowers from three blackcurrant (Ribes nigrum L.) cultivars, `Brödtorp', `Ben Tirran', and `Baldwin', was determined at two stages of floral development. The three cultivars together represent a large part of the available genetic base for this subgenus of Ribes. Plants were maintained either at 4 °C in a growth cabinet under a 16-hour photoperiod or outdoors in Scotland during Spring 1997. Observed genotypic differences in survival were not associated with differences in LT50 of the flowers, and observations of freezing damage to flowers on intact plants suggest that the flowers can often survive by supercooling. This hypothesis is partly confirmed by the finding that detached flowers from all three cultivars have the capacity to supercool to at least –9 °C. Ice nucleation in stem tissue, however, was found to occur at or above –2 °C. That flowers on intact plants can apparently survive by supercooling, together with the finding that ice nucleation in stem tissue occurs at temperatures well above the LT50 of flowers, indicate the presence of barriers to propagation of ice from stem tissue to raceme. Such barriers within individual racemes are also indicated by patterns of freezing damage to flowers on intact plants cooled to –5 °C.

Relationships between Floral Morphology, Breeding Behavior, and Flower Longevity in Easter Cactus

The effects of floral morphology and breeding behavior on flower longevity were investigated in Easter cactus [Hatiora ×graeseri (Werderm.) Barthlott)]. Four clones were studied: two diploid (n = 11) clones (`Evita' and `Purple Pride') that were highly self-incompatible (SI), and two cytochimeras (diploid epidermis and tetraploid subepidermis) that were recovered from the diploid cultivars, both of which were self-compatible (SC). The clones exhibited differences in the stage of floral development in which autogamy commenced. Autogamy commenced on the day of anthesis in the two `Evita' clones and occurred ≈5 days after anthesis in the `Purple Pride' cytochimera. In the `Purple Pride' diploid clone, anthers and stigmatic lobes remained spatially separated during the period from anthesis to senescence. Examination of styles collected from senesced, undisturbed flowers showed that few pollen tubes traversed to the base of the styles for the two SI diploid clones, whereas large numbers of pollen tubes were present at the base of the styles for the two SC cytochimeras. Flower longevity for the `Evita' cytochimera was significantly less than for `Evita' diploid, but the diploid and cytochimeral clones of `Purple Pride' exhibited similar flower longevities. Application of 2 mm silver thiosulfate, an inhibitor of ethylene (C2H4) action, did not affect flower longevity of `Evita' cytochimera. Our results show that flower longevity in Easter cactus is influenced by breeding behavior and the stage of floral development at which autogamy commences.

低温処理温度の違いがフリージアの開花に及ぼす影響

In Japan, freesia corms after root emergence are precooled at 8 to 10°C under moist condition for 5 to 7 weeks to advance flowering. Because flower initiation and differentiation occur under these conditions, low temperatures enhance it directly. In these experiments, we tested the effects of chilling temperatures on flowering were direct or an indirect ones on freesia corms of 'Elegance' and 'Blue Heaven' by keeping the corms at 5, 8, 10, 12, or 15°C under moist condition. They were then moved to 24/18°C (day/night) at the same stage of floral development. Corms chilled at 5°C for 13 weeks did not initiate flower buds, and were excluded from the experiments. Within a range of 8 to 15°C, not only a direct effect but also some after-effects on flowering were noticed. The number of florets per main inflorescence was determined as a direct effect of chilling temperature ; it decreased as corms were chilled at lower temperatures. Corms, chilled at lower temperatures, also had a higher flowering percentage and longer flower stem, and required fewer days from the end of chilling to flowering ; an after-effect of the chilling temperature.

Flowering response of Eremurus to post-harvest temperatures

The influence of post-harvest temperature on the flowering response of the ornamental geophyte Eremurus was studied. The plants were harvested at four different stages of development and were separated into three groups. The first group was immediately exposed to 2°C, the second group to 20°C followed by 2°C, and the third group to 20°C followed by 32°C and, subsequently, 2°C. Scanning electron microscopy (SEM) was used for concurrent morphological analysis of floral development. Application of 2°C to the plants in the initial stage of floral development caused plant destruction and death, while the same treatment applied at the stage of full differentiation promoted normal flowering. Temperatures of 20°C and, especially, 32°C, significantly improved flowering of the plants harvested in the early stages of florogenesis, whereas the same treatment applied to the plants harvested at the end of flower differentiation did not affect the flowering process. A developmental disorder, which we term `interrupted floral development' (IFD), was observed only in the plants harvested when the racemes were fully differentiated. This was probably caused by the very high air and soil temperatures that prevail in Israel during the summer. The extent of floral differentiation has a determinant role in subsequent scape elongation and flowering.

Growth relationships of individual flowers during late stages of floral development of Rhododendron L. 'Prize' and 'Gloria'

Single terminal inflorescences from two-stemmed plants of Rhododendron L. cv. 'Prize' and 'Gloria' were recurrently sampled during a 9°C cold treatment and subsequent forcing period in an 18°C growth chamber until plants reached anthesis. At each sample period, bud length and width were measured on each inflorescence, while subtending bud scale, petal, stamen ('Gloria' only), style, peduncle and ovary length, ovary width, and flower weight were determined on the two most basally attached flowers within an inflorescence for each cultivar. Polynomial regression models were calculated for each floral growth measurement over time, except for bud length and width, for each of the four flowers within a cultivar. Comparison of regression models revealed differences in floral part growth patterns among the various flowers within each cultivar. During the first week of placement in 18°C forcing temperatures after the cold treatment, bud length was the only floral part to grow on 'Prize' plants, while only female flower parts grew on 'Gloria' plants. These results indicate differences in growth resumption patterns between cultivars after cold storage. However, petal and style length were strongly correlated to flower weight for both cultivars indicating that these measurements could be used in laboratory or field situations to determine the floral stage of growth. The growth equations described would be useful for controlling the variability among shoots and flowers for analytical determinations, such as hormonal content analysis, and for studying relationships of floral growth patterns to environmental stimuli that could be used to control flowering. The statistical techniques used in this research make it possible to reduce the number of plants for such studies, as measurements taken on different flowers on the same plant can be used for floral part growth comparisons despite the inherent correlation present between such measurements.Key words: morphology, dormancy, growth modeling, multivariate multiple regression, controlled environment.