Academic literature on the topic 'Umbel inflorescence'

Abstract Hybridization in celery is a difficult task faced by the breeder due to the complex floral biology. Celery flowers are hermaphroditic but protandrous and are arranged in compound inflorescences or umbels, formed by small groups of flowers or umbellets disposed in whorls (3). The different developmental stages of the flowers in the umbel makes it difficult to control pollinations effectively. Pollen from young flowers will pollinate old ones that have receptive stigmas in the same inflorescence or anywhere else on the plant. Honma (4) reported a useful technique for celery hybridization, which is the standard procedure used today by breeders. The accuracy of this method depends on the faithful drop of stamens before any of the stigmas become receptive; otherwise, accidental self-pollinations will occur.

Two new species of Dendropanax (Araliaceae) endemic to Costa Rica are described. Dendropanax aberrans J.F. Morales resembles D. grandiflorus but differs by the inflorescence structure (panicle of umbels vs. single umbel), and the smaller sizes of both the hypanthium and the petals. Dendropanax zarratu J.F. Morales is unique among Central America and West Indian taxa. It is recognized by its panicle of umbels, with the peduncles agglomerate, flowers 8-9-merous, hypanthium 7-8 mm long, and fruits 1.2-1.4 cm long. Illustrations of the new species and a key to the four Dendropanax having elongated hypanthia (≥ 4 mm long) in Mexico, Central America, the West Indies, and Colombia are provided.

The activity of bees pollination in onion was observed throughout the day. Numerically maximum activity was observed during afternoon hours (12.00 to 2.00 PM) with 7.00 numbers in rock bee, 5.40 in Indian bees, 11.60 in little bees and 7.80 in case of dammer be, respectively. Among the four species of bees, little bees were more in entire day with highest of 111.60 bees/10 inflorescence/ minute followed by dammer bee with 9.40 bees/10 inflorescence/ minute, Among the bees major contributor was little bee, this may be due to more colonies of little bees in that area and destruction of rock bee colonies. Also, the bee acitivty was observed maximum number at 100 per cent flowering stage. The observations on number of seeds per umbel, 1000 seed weight and per cent germination under the laboratory conditions. The results clearly indicated that, maximum number of seeds per umbel was observed in open pollinated flowers with 339.30 ± 60.27 seeds per umber where all the four species of bees were made visits regularly followed by in case of pollination in mesh cloth cage with bees with 330.00±35.80 and very least number of seed set was observed in case of pollination in mesh cloth cage without bees with only 60.70 seeds/umbel. Similarly, 1000 seed weight also differed significantly in case of pollination with bees and without bees. In case of with bees it weighed around 3.37 g/1000 seeds followed by 3.10 g/1000 seeds in onion with bee cage and least in case of control with only 1.97 g/1000 seeds.

The article considers the synflorescence structure of five little-studied and endemic representatives ofUmbelliferae (Apiaceae Lindl.) from Central Asia. Among the taxa studied, Komarovia anisosperma is distinguished bya special organization of the inflorescence, and which is represented by the type of storey raceme from open double umbels collected 2–6 in whorls. The remaining species are characterized by one type of inflorescence – this is a panicle ofclosed double umbels. Belonging to the same tribe Komarovieae J. Zhou et S. R. Downie, species Komarovia anisosperma and Sphaerosciadium denaense, have some similar features in the structure of the synflorescence. So, the first specieshas 5 lateral axes of the I order around the main axis assembled in whorls, while in the second species they are locatedwith a whorl under the central umbel , in addition, both species do not have involucres and involucels. The revealedfeatures of branching of the inflorescence and flower arrangement, signs of involucres and involucels, the length of therays of the umbels and pedicels, as well as the characteristic of the formation of various types of flowers in the umbeland synflorescence can be used in keys and diagnoses, and also for the conservation of rare and endemic species, forthe collection of made seeds from plants in natural conditions with further introduction to the botanical gardens or onthe protected areas.

Thunbergia amphaii, a new species from North-Eastern Thailand is described and illustrated. The pseudo-umbel inflorescence is diagnostic for this species. The pollen morphology, especially the size and the pericolpate aperture arrangement, further support this species as new to science.

Thunbergia amphaii, a new species from North-Eastern Thailand is described and illustrated. The pseudo-umbel inflorescence is diagnostic for this species. The pollen morphology, especially the size and the pericolpate aperture arrangement, further support this species as new to science.

Allium moly subsp. glaucescens is described as a new subspecies from the Iberian Peninsula. Different morphological characters from populations located in Valencia (Spain) are evidenced. Lower size of plants, smaller and narrower leaves, of noticeably bluish-green color (glaucous-pruinose), smaller and less flowers in the umbel-inflorescence are characteristic of the new subspecies. Ecology, habitat, cultivation and chemotaxonomy have also been considered and discussed in this work.

Paepalanthus cordatus is an endangered species described from a single collection which lacks fully developed inflorescences and flowers. Despite the absence of these characters, the species was unambiguously placed in P. sect. Diphyomene, one of the few groups of Paepalanthus with dimerous flowers and which is mainly distributed in central Brazil. In this manuscript, I provide a full description of the species, detailing and illustrating the fully developed inflorescences and flowers for the first time. The spherical umbel-shaped inflorescence is composed of sets of capitula bearing dimerous flowers; the pistillate flowers have dolabriform sepals and bifid stigmatic branches; the staminate ones have an elongated fleshy anthophore. These characters fully match the current circumscription of P. sect. Diphyomene. Based on the specimens recently collected and additional data, the new conservation status for the species is Endangered instead of Critically Endangered, as previously assessed. I also clarify the inadvertent lectotype selection and previous interpretations of the type specimens. Comments on the species distribution, morphology, and ecology, as well as a geographic distribution map, photos, and a detailed illustration are also provided.

In 2011, carrot (Daucus carota L.) seed production occurred on 2,900 ha, which accounts for approximately 25% of the area devoted to the production of vegetable fine seeds. Since 2007, symptoms of umbel browning have been regularly observed in carrot production areas located in the central region. Initially, triangular necrotic lesions appeared on carrot umbels that later spread to the entire umbels and often progressed to the stems. Diseased umbels became dried prematurely, compromising seed development. The loss in seed production was estimated at approximately 8% of the harvested carrot umbels during the cropping seasons of spring and summer 2007 and 2008 in France. In collaboration with seed companies, diseased carrot stems were collected from seven fields of seed production (eight plants per field) and a fungus was isolated from the tissue. The cultures were grown on malt (2%) agar (1.5%) medium and incubated for 2 weeks at 22°C in darkness. Young fungal colonies were white and a brownish green pigmentation developed when the colonies became older. The same color was observed from the top and on the reverse of the colonies. To induce sporulation, isolates were grown on water agar (1.5%) medium in the presence of carrot stem fragments for 1 week at 22°C in darkness, followed by 1 week at 22°C in white light under a 16-h photoperiod. Pycnidia were produced on stem fragments and contained alpha and beta conidia typical of the genus Diaporthe (2). Alternatively, pycnidia were also obtained on malt agar medium after 2 weeks of culture at 25°C in white light under a 12-h photoperiod. The size of alpha and beta conidia was 6.3 ± 0.5 × 2.3 ± 0.4 μm and 23.3 ± 1.8 × 0.9 ± 0.2 μm, respectively (n = 170). In order to confirm the identification at the genus level and determine the species, DNA was extracted from the mycelium of three representative isolates and the ITS regions of the ribosomal DNA were amplified using universal primers (1). The sequences of the amplified products (GenBank Accession Nos. KF240772 to KF240774) were 100% identical with the ITS sequence of a Diaporthe angelicae isolate deposited in the NCBI database (CBS 111592 isolate, KC343027). To confirm pathogenicity, the three isolates of D. angelicae were inoculated on carrot umbels in the greenhouse. A total of nine plants were inoculated (three plants per isolate). Using a micropipette, 10 μl of a conidial suspension containing alpha and beta conidia (105 conidia mL–1) were deposited at the base of the primary umbel and two secondary umbels, which were wounded before inoculation using a scalpel blade. Seven inoculated plants developed triangular, necrotic lesions that were typical umbel browning. D. angelicae was re-isolated on malt agar medium from the inoculated diseased carrot umbels. To our knowledge, this is the first report of D. angelicae in carrot cultivated for seed production in France. The disease resembles the lesions described in the Netherlands in 1951 on carrot inflorescence caused by Phomopsis dauci (3). In future experiments, it would be crucial to precisely determine if D. angelicae could be transmitted to the seeds. References: (1) M. A. Innis et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990. (2) J. M. Santos and A. J. L. Philips. Fungal Divers. 34:111, 2009. (3) J. A. von Arx. Eur. J. Plant Pathol. 57:44, 1951.

Smilax auriculata produces a subterranean rhizome system and an aerial vegetative branching system. Three intergrading types of stems (types 1, 2, and 3) compose the aerial branching system; these types are identified primarily according to prickle concentration, but also differ from one another in additional ways. Type-3 stems are determinate and either proleptic or precocious. Between growing seasons a foliage leaf of a type-3 stem may subtend either a solitary vegetative bud (or an expanded vegetative branch) or an inflorescence superposed over a vegetative bud (or expanded vegetative branch). Occasionally, an inflorescence terminates a type-3 stem. Whereas, rhizomes exhibit solely scale leaves, the aerial vegetative branching system manifests scale leaves, transitional leaves, and foliage leaves. On many type-3 stems the foliage leaves become oriented skyward, by bending of their leaf sheaths and petioles. The aerial vegetative branching system manifests bilateral symmetry and mirror-image symmetry. The inflorescence is a pedunculate umbel. The peduncle culminates in a torus which bears a peripheral whorl of bracts, centripetally situated bracteoles, and pedicellate flowers. Type-1 stems exhibit numerous prickles, which vary from unbranched to branched and from solitary to basally connate in rows.

Doctor of Philosophy (PhD)
A renewed focus on generalised pollinator systems has inspired a conceptual framework which highlights that spatial and temporal interactions among plants and their assemblage of pollinators can vary across the individual, population, regional and species levels. Pollination is clearly a dynamic interaction, varying in the number and interdependence of participants and the strength of the outcome of the interaction. Therefore, the role of variation in pollination is fundamental for understanding ecological dynamics of plant populations and is a major factor in the evolution and maintenance of generalised and specialised pollination systems. My study centred on these basic concepts by addressing the following questions: (1) How variable are pollinators in a generalised pollination system? To what degree do insect visitation rates and assemblage composition vary spatially among populations and temporally among flowering seasons? (2) How does variation in pollinators affect plant reproductive success? I chose to do this using a model system, Trachymene incisa subsp. incisa (Apiaceae), which is a widespread Australian herbaceous species with simple white flowers grouped into umbels that attract a high diversity of insect visitors. The Apiaceae are considered to be highly generalist in terms of pollination, due to their simple and uniform floral display and easily accessible floral rewards. Three populations of T. incisa located between 70 km and 210 km apart were studied over 2-3 years. The few studies investigating spatial and temporal variation simultaneously over geographic and yearly/seasonal scales indicate that there is a trend for more spatial than temporal variation in pollinators of generalist-pollinated plants. My study showed both spatial and temporal variation in assemblage composition among all populations and variation in insect visitation rates, in the form of a significant population by year interaction. However, removing ants from the analyses to restrict the assemblage to flying insects and the most likely pollinators, resulted in a significant difference in overall visitation rate between years but no difference in assemblage composition between the Myall Lakes and Tomago populations. These results indicate more temporal than spatial variation in the flying insect visitor assemblage of T. incisa. Foraging behaviour provides another source of variation in plant-pollinator interactions. Trachymene incisa exhibits umbels that function as either male or female at any one time and offer different floral rewards in each phase. For successful pollination, pollinators must visit both male and female umbels during a foraging trip. Insects showed both preferences and non-preferences for umbel phases in natural patches where the gender ratio was male biased. In contrast, insects showed no bias in visitation during a foraging trip or in time spent foraging on male and female umbels in experimental arrays where the gender ratio was equal. Pollinator assemblages consisting of a mixture of different pollinator types coupled with temporal variation in the assemblages of populations among years maintains generalisation at the population/local level. In addition, spatial variation in assemblages among populations maintains generalisation at the species level. Fire alters pollination in T. incisa by shifting the flowering season and reducing the abundance of flying insects. Therefore, fire plays an important role in maintaining spatial and temporal variation in this fire-prone system. Although insect pollinators are important in determining the mating opportunities of 90% of flowering plant species worldwide, few studies have looked at the effects of variation in pollinator assemblages on plant reproductive success and mating. In T. incisa, high insect visitation rates do not guarantee high plant reproductive success, indicating that the quality of visit is more important than the rate of visitation. This is shown by comparing the Agnes Banks and Myall Lakes populations in 2003: Agnes Banks received the highest visitation rate from an assemblage dominated by ants but produced the lowest reproductive output, and Myall Lakes received the lowest visitation rate by an assemblage dominated by a native bee and produced the highest seedling emergence. Interestingly, populations with different assemblage composition can produce similar percentage seed set per umbel. However, similar percentage seed set did not result in similar percentage seedling emergence. Differences among years in reproductive output (total seed production) were due to differences in umbel production (reproductive effort) and proportion of umbels with seeds, and not seed set per umbel. Trachymene incisa is self-compatible and suffers weak to intermediate levels of inbreeding depression through early stages of the life cycle when seeds are self-pollinated and biparentally inbred. Floral phenology, in the form of synchronous protandry, plays an important role in avoiding self-pollination within umbels and reducing the chance of geitonogamous pollination between umbels on the same plant. Although pollinators can increase the rate of inbreeding in T. incisa by foraging on both male and female phase umbels on the same plant or closely related plants, most consecutive insect movements were between plants not located adjacent to each other. This indicates that inbreeding is mostly avoided and that T. incisa is a predominantly outcrossing species, although further genetic analyses are required to confirm this hypothesis. A new conceptual understanding has emerged from the key empirical results in the study of this model generalised pollination system. The large differences among populations and between years indicate that populations are not equally serviced by pollinators and are not equally generalist. Insect visitation rates varied significantly throughout the day, highlighting that sampling of pollinators at one time will result in an inaccurate estimate and usually underestimate the degree of generalisation. The visitor assemblage is not equivalent to the pollinator assemblage, although non-pollinating floral visitors are likely to influence the overall effectiveness of the pollinator assemblage. Given the high degree of variation in both the number of pollinator species and number of pollinator types, I have constructed a model which includes the degree of ecological and functional specialisation of a plant species on pollinators and the variation encountered across different levels of plant organisation. This model describes the ecological or current state of plant species and their pollinators, as well as presenting the patterns of generalisation across a range of populations, which is critical for understanding the evolution and maintenance of the system. In-depth examination of pollination systems is required in order to understand the range of strategies utilised by plants and their pollinators, and I advocate a complete floral visitor assemblage approach to future studies in pollination ecology. In particular, future studies should focus on the role of introduced pollinators in altering generalised plant-pollinator systems and the contribution of non-pollinating floral visitors to pollinator assemblage effectiveness. Comparative studies involving plants with highly conserved floral displays, such as those in the genus Trachymene and in the Apiaceae, will be useful for investigating the dynamics of generalised pollination systems across a range of widespread and restricted species.