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At least 181 records · Page 10Linked to original sources
PubMed2005

Rain forest provides pollinating beetles for atemoya crops.

Small beetles, usually species of Nitidulidae, are the natural pollinators of atemoya (Annona squamosa L. x A. cherimola Mill. hybrids; custard apple) flowers but commercial atemoya growers often need to carry out labor-intensive hand pollination to produce enough high-quality fruit. Because Australian rain forest has plant species in the same family as atemoya (Annonaceae) and because many rain forest plants are beetle pollinated, we set out to discover whether tropical rain forest in far north Queensland harbors beetles that could provide this ecosystem service for atemoya crops. Orchards were chosen along a gradient of increasing distance from tropical rain forest (0.1-24 km). We sampled 100 flowers from each of nine atemoya orchards and determined the identity and abundance of insects within each flower. To assess the amount of pollination due to insects, we bagged six flowers per tree and left another six flowers per tree accessible to insects on 10 trees at an orchard near rain forest. Results indicated that atemoya orchards < or = 0.5 km from rain forest were predominantly visited by five previously unrecognized native beetle pollinators that are likely to originate in tropical rain forest. These native beetles occurred reliably enough in crops near rain forest to have a positive effect on the quantity of fruit produced but their contribution was not great enough to satisfy commercial production needs. Management changes, aimed at increasing native beetle abundance in crops, are required before these beetles could eliminate the need for growers to hand pollinate atemoya flowers. Appreciation of the value of this resource is necessary if we are to develop landscapes that both conserve native biodiversity and support agricultural production.

Agriculture↗
PubMedDate not supplied

[Seed set analysis in three amaranth species (A. cruentus, A. caudatus, and A. lividus) under self- and cross-pollination conditions].

Seed set was analyzed in three amaranth species (A. cruentus, A. caudatus, and A. lividus) under conditions of self- and cross-pollination during four vegetative periods in 1995-1998. It was demonstrated, that the populations of these species are polymorphic for the breeding system and that they consist of self-sterile and self-fertile plants. The populations were composed mostly of self-sterile plants and the percentages of self-fertile plants were only 34.7%, 18.7%, and 12.5% for A. cruentus, A. caudatus, and A. lividus respectively. The level of self-fertility was high in the first year of isolation, it sharply decreased during the subsequent years of selfing, due to inbreeding effect. Seed set under self- and cross-pollination is determined by species-specificity of the plants, influence of conditions of their growth, and inbreeding depression. Conditions of growth had the strongest influence on seed set. Index of its influence varied from 0.53 to 0.87 for the cross-pollinated plants and from 0.13 to 0.68 for the self-pollinated ones. Analysis of variance demonstrated a weak effect of the interaction of these factors. Spearman's rank correlation demonstrated a highly significant agreement between the seed set values for the self- and cross-pollinated plants of A. cruentus and A. lividus. The lines derived from the three amaranth species varied widely in the seed set values under both self- and cross-pollination conditions.

Amaranthus↗
PubMed1991

Number of beta-receptors in rhinitic pollinic patients.

The study was carried out on venous blood from 67 patients with seasonal rhinoconjunctivitis caused by sensitization to grass pollen and 30 control individuals. Total IgE determination, antigen-specific histamine release test against two concentrations of Phleum pratense, and quantification of beta 2-adrenergic receptor numbers in lymphocyte membrane of peripheral blood were done on all patients. Those pollinic patients who were asymptomatic at the time of the study had 500.07 +/- 237.27 receptors/cell; no significant differences were established with the control group, with 541.53 +/- 123.63 receptors/cell. However, both the control group and asymptomatic patients had receptor numbers which were significantly higher than those of symptomatic pollinic patients, with 376.81 +/- 158.65 receptors/cell (p < 0.01 and p < 0.05, respectively). The average decrease in number of receptors in symptomatic pollinic patients was 30.42% in relation to controls and 24.65% in relation to asymptomatic patients. Within the subgroup of pollinic patients, studied both in and out of season, the number of beta 2-adrenergic receptors had an average decrease of 13.22% during pollination, with 363.7 receptors/cell. Once the pollination season was over, this figure increased to 419.1 receptors/cell, establishing significant differences with p < 0.025. The number of beta 2-adrenergic receptors did not correlate with total seric IgE figures or with antigen-specific histamine release. These data indicate that the decrease of these receptors does not constitute the causal factor of atopic diseases; it seems more likely to be a consequence of the same.

Adolescent↗
PubMed2002

[The ultracytochemical localization of ATPase activity in pollen tube and stigma of Fagopyrum esculentum after compatible and incompatible pollination].

Ultracytochemical localization of adenosine triphosphatase (ATPase) activity in stigmas, pollens and pollen tubes of Fagopyrum esculentum was performed with the cytochemical method of lead phosphate precipitation. The results were as follows: (1) Lower activities of ATPase appeared in stigma cells at 0.5 hour after compatible and incompatible pollination. Stigma surface and pollen grains attached on stigma showed higher ATPase activities after compatible pollination and lower or no activities after incompatible pollination at 0.5 hour. ATPase localized on endoplasmic reticula and sperm cell in pollen grain. (2) Lower ATPase activities appeared both in stigma cells and pollen tubes in style at 1.5 hours after incompatible pollination. Pollen tube stopped growing and the degeneration of its cytoplasma began; on the contrary, at 1.5 hours after compatible pollination, higher ATPase activities were detected both in stigma cells and pollen tube in style. ATPase localized mainly on plasmolemma, in cytoplasmic matrix of stigma cells and in mitochondria, dictyosome, plastid envelop, and on the wall of pollen tube as well. The present study indicated that the stop of pollen tube growth after self-incompatibility of Fagopyrum esculentum resulted not only from the nutrient starvation of pollen tube, but also from its metabolic disorder in incompatible style.

Adenosine Triphosphatases↗
PubMed1996

Pollinator Foraging Strategies in Mixed Floral Arrays: Density Effects and Floral Constancy

The profitability of any foraging strategy may be in part dependent on the number of foragers adopting it, and so it can be viewed mathematically as a "game." We explore here the implications of a game-theoretic model of pollinators foraging on a mixed array of two flower species, with individual pollinators either specializing on one or the other, or else acting as generalists. We further allow for the possibility of specialist advantages in foraging efficiency. The predicted mixture of pollinator behavioral strategies depends on the overall floral density and the relative densities of the two flower species. Where floral resources are scarce, pollinators should behave as generalists whereas when resources are superabundant, specialization on the single most profitable flower type (all else being equal, the commonest one) is favored. At intermediate floral densities, a mix of floral specializations (floral constancy) is favored, so long as the rarer flower's density does not fall below some critical minimum level. Where the rarer flower is too rare, a mixture of generalists and common-species specialists is favored. Rare flowers are at a reproductive disadvantage in all cases, but their relative success is highest where their pollinators are flower constant.

Journal Article↗
PubMed2002

Dynamics of herbivore-plant-pollinator models.

A mathematical model for the plant-pollinator interaction for which the relationship is not obligate is discussed. The dynamics of the system depend on both the energetic rewards and the specificity of the pollinator to the plant. Based on this model, the interaction between herbivore, plant and pollinator is proposed and the possible effect of reducing pollinator visitation rate due to the presence of herbivore is considered. It is shown that this reduction mechanism has no effect on the qualitative behavior of the model. By using these results, the possible mechanism of enhancing pollinator visitation rate accompanied by the herbivore upon the system is also examined. It is demonstrated that such a mechanism in general can promote the persistence of this three population interaction.

Animals↗
PubMed2000

Late steps of egg cell differentiation are accelerated by pollination in Zea mays L.

Egg cells were analysed cytologically during the female receptivity period in maize (Zea mays L., line A 188). Three classes of egg cell were distinguished: type A--small, non-vacuolated cells with a central nucleus; type B--larger cells with small vacuoles surrounding the perinuclear cytoplasm located in the middle of the cell; type C--big cells with a large apical vacuole and the mid-basal perinuclear cytoplasm. The less-dense cytoplasm of the vacuolated egg cells usually contained numerous cup- or bell-shaped mitochondria. The three egg types appear to correspond to three late stages of egg cell differentiation. The frequencies of each of the three egg types were monitored in developing maize ears before and after pollination. In young ears, with the silks just extending out of the husks, small A-type cells were found in about 86% of ovules. Their frequency decreased to about 58% at the optimum silk length, remained unchanged in non-pollinated ears, and fell to 16% at the end of the female receptivity period. However, after pollination and before fertilisation the frequency of these cells decreased to about 33%, and the larger vacuolated egg cells (types B and C) prevailed. At various stages of the receptivity period, pollination accelerated changes in the egg population, increasing the number of ovules bearing larger, vacuolated egg cells. Experiments with silk removal demonstrated that putative pollination signals act immediately after pollen deposition and are not species-specific.

Cell Differentiation↗
PubMed2003

Sex and pollen: the role of males in stabilising a plant-seed eater pollinating mutualism.

Some plants are exclusively pollinated by an insect whose larvae feed on their seeds. The net outcome of a single visit for the plant depends on the number of ovules fertilised by the visitor, the number of eggs laid, and the number of seeds eaten by each larva. Unlike other known plant-seed eater pollinating mutualisms, the globeflower-globeflower fly mutualism (Trollius europaeus-Chiastocheta spp.) is unique in that not only females but also males visit flowers, and both sexes are potential pollinators. I analysed the relative efficiency of Chiastocheta males versus females in transporting pollen and fertilising globeflower ovules. I show that there is no sex-specific morphological adaptation or behaviour to enhance pollen collection and transportation in Chiastocheta flies, and that males contribute to pollination. However, because of their smaller body size, males transport significantly less pollen than females. Less seeds are produced after a visit from a male than after a visit from a female. A single female visit contributes to about 12% of total seed production, and a single male visit to only 5.4%. Females tend to spend more time inside the flower than males, and the number of ovules fertilised is significantly correlated with the time insects spent inside the closed corolla. The lower efficiency of ovule fertilisation by a male's single visit is compensated for by the higher rate of flower visitation by males: a flower receives about twice as many visits from males as from females during a time unit. The contribution of males to pollination is of major importance with respect to understanding the evolutionary stability of the globeflower-globeflower fly mutualism, as males satiate pollen requirement of flowers, masking the antagonistic effect of ovipositing females.

Adaptation, Physiological↗
PubMed2004

Do floral syndromes predict specialization in plant pollination systems? An experimental test in an "ornithophilous" African Protea.

We investigated whether the "ornithophilous" floral syndrome exhibited in an African sugarbush, Protea roupelliae (Proteaceae), reflects ecological specialization for bird-pollination. A breeding system experiment established that the species is self-compatible, but dependent on visits by pollinators for seed set. The cup-shaped inflorescences were visited by a wide range of insect and bird species; however inflorescences from which birds, but not insects, were excluded by wire cages set few seeds relative to open-pollinated controls. One species, the malachite sunbird (Nectarinia famosa), accounted for more than 80% of all birds captured in P. roupelliae stands and carried the largest protea pollen loads. A single visit by this sunbird species was enough to increase seed set considerably over unvisited, bagged inflorescences. Our results show that P. roupelliae is largely dependent on birds for pollination, and thus confirm the utility of floral syndromes for generating hypotheses about the ecology of pollination systems.

Adaptation, Physiological↗
PubMed2004

Bottom-up effects of nutrient availability on flower production, pollinator visitation, and seed output in a high-Andean shrub.

Soil nutrient availability directly enhances vegetative growth, flowering, and fruiting in alpine ecosystems. However, the impacts of nutrient addition on pollinator visitation, which could affect seed output indirectly, are unknown. In a nutrient addition experiment, we tested the hypothesis that seed output in the insect-pollinated, self-incompatible shrub, Chuquiraga oppositifolia (Asteraceae) of the Andes of central Chile, is enhanced by soil nitrogen (N) availability. We aimed to monitor total shrub floral display, size of flower heads (capitula), pollinator visitation patterns, and seed output during three growing seasons on control and N addition shrubs. N addition did not augment floral display, size of capitula, pollinator visitation, or seed output during the first growing season. Seed mass and viability were 25-40% lower in fertilised shrubs. During the second growing season only 33% of the N addition shrubs flowered compared to 71% of controls, and a significant (50%) enhancement in vegetative growth occurred in fertilised shrubs. During the third growing season, floral display in N addition shrubs was more than double that of controls, received more than twice the number of insect pollinator visits, and seed output was three- to four-fold higher compared to controls. A significant (50%) enhancement in vegetative growth again occurred in N addition shrubs. Results of this study strongly suggest that soil N availability produces strong positive bottom-up effects on the reproductive output of the alpine shrub C. oppositifolia. Despite taking considerably longer to be manifest in comparison to the previously reported top-down indirect negative effects of lizard predators in the same study system, our results suggest that both bottom-up and top-down forces are important in controlling the reproductive output of an alpine shrub.

Animals↗
PubMed2005

Relationships between species' floral traits and pollinator visitation in a temperate grassland.

Knowledge about plant-plant interactions for pollinator service at the plant community level is still scarce, although such interactions may be important to seed production and hence the population dynamics of individual plant species and the species compositions of communities. An important step towards a better understanding of pollination interactions at the community level is to assess if the variation in floral traits among plant species explain the variation in flower visitation frequency among those species. We investigated the relative importance of various floral traits for the visitation frequency of all insects, and bumblebees and flies separately, to plant species by measuring the visitation frequency to all insect-pollinated species in a community during an entire flowering season. Visitation frequency was identified to be strongly positive related to the visual display area and the date of peak flowering of plant species. Categorical variables, such as flower form and symmetry, were important to the visitation frequency of flies only. We constructed floral similarity measures based on the species' floral traits and found that the floral similarity for all species' traits combined and the continuous traits separately were positively related to individual visitation frequency. On the other hand, plant species with similar categorical floral traits did not have similar visitation frequencies. In conclusion, our results show that continuous traits, such as flower size and/or density, are more important for the variation in visitation frequency among plant species than thought earlier. Furthermore, differences in visitation frequency among pollinator groups give a poor support to the expectations derived from the classical pollination syndromes.

Animals↗
PubMed2006

Geographic and within-population variation in the globeflower-globeflower fly interaction: the costs and benefits of rearing pollinators' larvae.

Interspecific interactions can vary within and among populations and geographic locations, and this variation can influence the nature of the interaction (e.g. mutualistic vs. antagonistic) and its evolutionary stability. Globeflowers are exclusively pollinated by flies, whose larvae feed only on their seeds. Here we document geographic variability in costs and benefits in globeflowers in sustaining their pollinating flies throughout the range of this arctic-alpine European plant over several years. A total of 1,710 flower heads from 38 populations were analysed for their carpel, egg and seed contents. Individual and population analyses control for the confounding influences of variation in both: (1) population traits, such as fly density and egg distribution among flower heads; and (2) individuals traits, such as carpel and egg numbers per flower head. Despite considerable variation in ecological conditions and pollinator densities across populations, large proportions (range 33-58%) of seeds were released after predation, with a benefit-to-cost ratio of 3, indicating that the mutualism is stable over the whole globeflower geographical range. The stability of the mutualistic interaction relies on density-dependent competition among larvae co-developing in a flower head. This competition is revealed by a sharp decrease in the number of seeds eaten per larva with increasing larval number, and is intensified by non-uniform egg distribution among globeflowers within a population. Carpel number is highly variable across globeflowers (range 10-69), and flies lay more eggs in large flowers. Most plants within a population contribute to the rearing of pollinators, but the costs are greater for some than for others. Large globeflowers lose more seed to pollinator larvae, but also release more seed than smaller plants. The apparent alignment of interests between fly and plants (positive relationship between numbers of seed released and destroyed) is shown to hide a conflict of interest found when flower size is controlled for.

Analysis of Variance↗
PubMed2006

Post-pollination reproductive isolation between diurnally and nocturnally flowering daylilies, Hemerocallis fulva and Hemerocallis citrina.

To examine whether floral and post-pollination isolation develops independently or not, we conducted a crossing experiment between Hemerocallis fulva and Hemerocallis citrina that shows large floral divergence adapted for diurnal and nocturnal pollinators that have been believed to be fully cross-fertile. Flowers of the two species from sympatric populations were hand-pollinated with conspecific pollen from the same population (control), interspecific pollen from the same area (sympatric cross), and interspecific pollen from the different area (allopatric cross). After capsule dehiscence, the fruit set, seed set per fruit and seed set per flower were determined among three cross categories. The seed sets per flower were 32 and 77% lower in sympatric and allopatric crosses than in the control when H. fulva was the pollen recipient. There was no difference in three reproductive measures among the cross categories when H. citrina was the pollen recipient. This finding indicates that post-pollination isolation does exist between H. fulva and H. citrina, although it is partial, asymmetric, and weakened in sympatry. Our result suggests that floral and post-pollination isolation may develop independently, and reinforcement may not be a general phenomenon in plants.

Circadian Rhythm↗
PubMed2006

Fragrance of Canada thistle (Cirsium arvense) attracts both floral herbivores and pollinators.

The evolution of floral scent as a plant reproductive signal is assumed to be driven by pollinator behavior, with little attention paid to other potential selective forces such as herbivores. I tested 10 out of the 13 compounds emitted by dioecious Cirsium arvense, Canada thistle, including 2-phenylethanol, methyl salicylate, p-anisaldehyde, benzaldehyde, benzyl alcohol, phenylacetaldehyde, linalool, furanoid linalool oxides (E and Z), and dimethyl salicylate. Single compounds (and one isomer) set out in scent-baited water-bowl traps trapped over 10 species of pollinators and 16 species of floral herbivores. The two dominant components of the fragrance blend of C. arvense, benzaldehyde and phenylacetaldehyde, trapped both pollinators and florivores. Other compounds attracted either pollinators or florivores. Florivores of C. arvense appear to use floral scent compounds as kairomones; by advertising to pollinators, C. arvense also attracts its own enemies.

Acetaldehyde↗
PubMed2005

New insights into the phylogeny of fig pollinators using Bayesian analyses.

The interaction between figs and fig pollinators is one of the most species-specific mutualisms. Recently, phylogenies of both partners based on molecular data provided insights into a wide spectrum of co-evolutionary questions. However, for the phylogeny of fig pollinators, there are some discrepancies between different studies and left some relationships unresolved, especially for deep nodes. The phylogenetic uncertainties of pollinators prohibit our further understanding of the history of the mutualism. Here, we present phylogenetic analyses of a larger COI sequence dataset that includes previously published datasets and our sequences from 20 species using Bayesian method and maximum parsimony. The analyses using different methods share similar topologies. Bayesian analyses provide high level of confidence for most internal nodes in terms of posterior probability. This study also clarifies some discrepancies between previous studies. After rooting with Tetrapus, other pollinators split into two clades. Wiebesia and Blastophaga are at basal positions in respective clade. Ceratosolen is not monophyletic because Kradibia and Liporrhopalum fall inside this group. Three subgenera of Ceratosolen: subgen. Ceratosolen, subgen. Rothropus, and subgen. Strepitus are not supported. Therefore, Ceratosolen is suggested to be re-divided into three groups. Urostigma pollinators (including Dolichoris and Blastophaga psenes) are clustered together. The monophylies of Wiebesia, Blastophaga, Dolichoris are not supported in this analysis. This study also provides a new framework for re-evaluating character evolution and re-inspecting the definition of some genera.

Animals↗
PubMed2003

Spatially explicit modelling of transgenic maize pollen dispersal and cross-pollination.

Modelling of pollen dispersal and cross-pollination is of great importance for the ongoing discussion on thresholds for the adventitious presence of genetically modified material in food and feed. Two different modelling approaches for pollen dispersal are used to simulate the cross-pollination rate of pollen emerged from an adjacent transgenic crop field. The models are applied to cross-pollination data from field experiments with transgenic maize (Zea mays). The data were generated by an experimental setup specifically designed to suit the demands of mathematical modelling. First a Gaussian plume model is used for the simulation of pollen transport in and from plant canopies. This is a semiempirical approach combining the atmospheric diffusion equation and Lagrangian methodology. The second model is derived from the localised near field (LNF) theory and based on the physical processes in the canopy. Both modelling approaches prove to be appropriate for the simulation of the cross-pollination rates at distances of about 7.5m and more from the transgene source. The simulation of the cross-pollination rate is less precise at the edge of the source plot especially with the LNF theory. However, the simulation results lie within the range of variability of the observations. Concluding can be pointed out that both models might be adapted to other pollen dispersal experiments of different crops and plot sizes.

Environmental Pollution↗
PubMed2000

Generalization versus specialization in plant pollination systems.

The long-standing notion that most angiosperm flowers are specialized for pollination by particular animal types, such as birds or bees, has been challenged recently on the basis of apparent widespread generalization in pollination systems. At the same time, biologists working mainly in the tropics and the species-rich temperate floras of the Southern hemisphere are documenting pollination systems that are remarkably specialized, often involving a single pollinator species. Current studies are aimed at understanding: (1) the ecological forces that have favoured either generalization or specialization in particular lineages and regions; (2) the implications for selection on floral traits and divergence of populations; and (3) the risk of collapse in plant-pollinator mutualisms of varying specificity.

Journal Article↗
PubMed1999

Incompatibility and pollen competition in Alnus glutinosa: Evidence from pollination experiments.

Different types of incompatibility systems were found to operate simultaneously in Alnus glutinosa in the course of numerous pollination experiments, including self-pollination and pollination with controlled pollen mixtures. Isozyme genetic markers were used to identify the pollen parent of each offspring from the mixed pollination experiments, thus allowing specification of the fertilization success of each pollen parent. In a first step, these results were compared with observations on in vitro pollen germination experiments. This comparison allows for exploration of the explanatory value of different germination media as models of germination conditions on stigmas. In most cases, the data suggest that the in vitro germination conditions resemble the fertilization conditions in vivo, at least in the sense that they favor the same pollen parents. By providing a generic and operable definition of the two basic types of incompatibility, eliminating (inability to fertilize ovules) and cryptic (resulting in lowered fertilization success of a pollen parent under competition), evidence was detected for the existence of both types of incompatibility in Alnus glutinosa, where eliminating incompatibility occurred as self-incompatibility only. However, since this incompatibility seems to act primarily via pollen elimination, seed production is not likely to be negatively affected in natural populations, even for comparatively large amounts of self-pollination.

Journal Article↗