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Abstract Background Successive stamen movement is a complex plant behavior involving successive uplift of stamens and pollen release, which plays a role in reducing sexual interference, increasing pollen deposition and promoting pollen export. Although reported from several taxa, studies on whether the movement can be influenced by abiotic and biotic factors are scarce. Methods In this study, we here for the first time described a pattern of successive stamen movement in Saxifraga candelabrum (Saxifragaceae). We then compared the rates of stamen movement in S. candelabrum under different weather and varying pollinator visits. Pollen packaging and presentation schedule of S. candelabrum were also investigated. Results The results showed that the number of stamens bent per day in sunny days was significantly higher than overcast and rain. Flowers that receive more pollinator visits (control treatment) had significantly higher number of stamen movement than those that received fewer (removal treatment) and none (bagging treatment). Throughout the staminate phase of a flower, there was a progressive increase in both pollen quantity of individual stamens and pollen presentation during each day. Conclusion Our research demonstrates that successive stamen movement in S. candelabrum was accelerated by favorable weather and increased pollinator visits, which may promote pollen export. Moreover, incremental pollen packaging is likely an adaptation to seasonal regularity in variations of sex ratio resulting from protandry.

Management of food resources is considered fundamental for supporting insect pollinators, whose abundance shows a downward trend on the global scale. Here, the nectar and pollen production (per flower, per 1 m2 of tree crown), the composition of nectar carbohydrates and the levels of pollen proteins was evaluated in eight Tilia species (Malvaceae) growing in SE Poland. In the warm-summer continental climate, Tilia species can improve nectar and pollen resources mainly in June/July. Although the flowering period of each species is short (8.0–14.7 days), appropriate selection of species can extend the availability of food for more than a month. However, the considerable variations in the flowering onset (11.2–20.1 days) may cause significant inter-seasonal shifts in food accessibility. The nectar with its highly changeable sugar concentration (29.5–77.4%) was composed of sucrose, glucose, and fructose; protein content in pollen was 7.2–16.8%. The mean sugar yield was in the range of 0.95–19.1 g per 1 m2 (T. amuriensis – T. platyphyllos, respectively), whereas the mean pollen yield was 1.37–4.1 g per 1 m2 of tree crown (T. amuriensis – T. × euchlora, respectively). Significant year-to-year fluctuations of sugar and pollen yield in linden trees have to be taken into account in conservation schemes, and the introduction of other flowering plants with more stable sugar and pollen production should be considered in an area with a high density of linden trees. Linden flowers mainly support honey bees; nevertheless, wild pollinators (bumble bees, solitary bees, and dipterans) can also benefit from linden floral resources. [ABSTRACT FROM AUTHOR]

Background: Successive stamen movement is a complex plant behavior involving successive uplift of stamens and pollen release, which plays a role in reducing sexual interference, increasing pollen deposition and promoting pollen export. Although reported from several taxa, studies on whether the movement can be influenced by abiotic and biotic factors are scarce. Methods: In this study, we here for the first time described a pattern of successive stamen movement in Saxifraga candelabrum (Saxifragaceae). We then compared the rates of stamen movement in S. candelabrum under different weather and varying pollinator visits. Pollen packaging and presentation schedule of S. candelabrum were also investigated. Results: The results showed that the number of stamens bent per day in sunny days was significantly higher than overcast and rain. Flowers that receive more pollinator visits (control treatment) had significantly higher number of stamen movement than those that received fewer (removal treatment) and none (bagging treatment). Throughout the staminate phase of a flower, there was a progressive increase in both pollen quantity of individual stamens and pollen presentation during each day. Conclusion: Our research demonstrates that successive stamen movement in S. candelabrum was accelerated by favorable weather and increased pollinator visits, which may promote pollen export. Moreover, incremental pollen packaging is likely an adaptation to seasonal regularity in variations of sex ratio resulting from protandry. [ABSTRACT FROM AUTHOR]

Forest tree species reproduction is a key factor in maintaining the genetic diversity of future generations and the stability of forest ecosystems. The ongoing ash dieback disease could affect the reproductive ecology of Fraxinus excelsior L. and have a major impact on the quantity and quality of pollen and seeds. In this study, we investigated pollen production and viability of pollen and seeds of ash trees with different health status from 2018 to 2022. Inflorescences were collected from 105 trees (pollen production), pollen from 125 trees (pollen viability), and seeds from 53 trees (seed quality) in two seed orchards and in one floodplain forest in southern Germany. Not all parameters were examined at every site every year. The average pollen production per tree was estimated at 471.2 ± 647.9 billion pollen grains. In addition, we found that a high number of inflorescences did not equate to high pollen production per inflorescence. Pollen production of healthy and diseased trees did not differ significantly, although only 47% of severely diseased male trees (vs. 72% for healthy trees) produced flowers. With regards to pollen viability, the TTC test showed an average viability of 73% ± 17%. Overall, there was a slight tendency for diseased trees to have less viable pollen. However, a significant difference could only be calculated for trees in the floodplain forest. The percentage of germinable seeds in 2018 was 38% in the floodplain forest and 57% in one of the seed orchards. The percentage of viable seeds (TTC test) ranged from 17 to 22% in the orchards in 2020. Non-viable seeds were usually heavily infested by insects. In general, seed quality was not significantly different between healthy and diseased trees. Our results indicate that ash dieback affects flower formation and pollen viability but not pollen production or seed quality. Nevertheless, the fact that hardly any flowering was observed, especially for trees that were seriously affected, suggests a negative effect of ash dieback on reproductive performance. Thus, severely diseased trees will transfer their genes to a smaller extent to the next generation. [ABSTRACT FROM AUTHOR]

Pollen production and pollen quality in Prunus spinosa L. (Rosaceae), a common early-spring flowering plant from the temperate zone was evaluated. The species is an efficient pollen producer, as it can produce 0.23 mg of pollen per flower and 1.99 g of pollen per 1 m 2 of shrub surface, however, the values may differ considerably between seasons. Its pollen contains a high amount of proteins (22.1–34.2%). The total lipid content in the pollen ranged between 2.7 and 3.6%. The presence of omega-3, omega-6, and omega-9 fatty acids was found. Among omega-3 fatty acids, inflammation inhibitors, i.e., α-linolenic acid and arachidonic acid, were detected. The predominant mineral was potassium, followed by calcium and magnesium. P. spinosa pollen is an important ingredient of bee pollen loads containing 89.1–98.2% of Prunus pollen . P. spinosa should be recommended for planting in the agricultural landscape in order to support the early spring diet for pollinators.

Ongoing climatic changes have altered growing conditions for plants by limiting water availability and inducing unprecedented temperature increases, eliciting plant functional responses that compromise floral trait expression, reduce pollen production and promote early self‐pollination. In a controlled greenhouse study, plants of Collinsia heterophylla, an annual mixed‐mated hermaphrodite, were grown under temperature and water stresses. Floral trait responses and related effects on plant reproductive success were recorded. Plants grown under temperature and water stresses were shorter and had fewer leaves at flowering than control plants. Temperature‐stressed plants flowered earlier and had smaller flowers that produced fewer per capita pollen grains than control and water‐stressed plants. While lifetime flower production in plants experiencing temperature stress alone or water stress alone was similar to control plants, those receiving combined temperature and water stresses had significantly lower lifetime flower production. Abiotic stress did not affect investment in female traits such as ovule number per flower, but impacted male traits seen as fewer pollen grains per flower. In plants experiencing abiotic stress, an increase in autonomous self‐pollination was facilitated through a compromise in herkogamy, a sexual interference mechanism that promotes cross‐pollination. Spatial separation between stigma and anther, a measure of herkogamy was zero or negative in stressed plants. Thus, abiotic stress responses in plants did not compromise plant reproductive success as autonomous selfing was augmented. In nature, such responses will likely reduce available nutrition for pollinators through decreased flower and pollen production. [ABSTRACT FROM AUTHOR]

In plants, the timely degeneration of tapetal cells is essential for providing nutrients and other substances to support pollen development. Rapid alkalinization factors (RALFs) are small, cysteine-rich peptides known to be involved in various aspects of plant development and growth, as well as defense against biotic and abiotic stresses. However, the functions of most of them remain unknown, while no RALF has been reported to involve tapetum degeneration. In this study, we demonstrated that a novel cysteine-rich peptide, EaF82, isolated from shy-flowering 'Golden Pothos' (Epipremnum aureum) plants, is a RALF-like peptide and displays alkalinizing activity. Its heterologous expression in Arabidopsis delayed tapetum degeneration and reduced pollen production and seed yields. RNAseq, RT-qPCR, and biochemical analyses showed that overexpression of EaF82 downregulated a group of genes involved in pH changes, cell wall modifications, tapetum degeneration, and pollen maturation, as well as seven endogenous Arabidopsis RALF genes, and decreased proteasome activity and ATP levels. Yeast two-hybrid screening identified AKIN10, a subunit of energy-sensing SnRK1 kinase, as its interacting partner. Our study reveals a possible regulatory role for RALF peptide in tapetum degeneration and suggests that EaF82 action may be mediated through AKIN10 leading to the alteration of transcriptome and energy metabolism, thereby causing ATP deficiency and impairing pollen development. [ABSTRACT FROM AUTHOR]

Pollen plays a key role in plant reproductive biology. Despite the long history of research on pollen and pollination, recent advances in pollen‐tracking methods and statistical approaches to linking plant phenotype, pollination performance, and reproductive fitness yield a steady flow of exciting new insights. In this introduction to the Special Issue "Pollen as the Link Between Phenotype and Fitness," we start by describing a general conceptual model linking functional classes of floral phenotypic traits to pollination‐related performance metrics and reproductive fitness. We use this model as a framework for synthesizing the relevant literature, highlighting the studies included in the Special Issue, and identifying gaps in our understanding and opportunities for further development of the field. The papers that follow in this Special Issue provide new insights into the relationships between pollen production, presentation, flower morphology, and pollination performance (e.g., pollen deposition onto stigmas), the role of pollinators in pollen transfer, and the consequences of heterospecific pollen deposition. Several of the studies demonstrate exciting experimental and analytical approaches that should pave the way for continued work addressing the intriguing role of pollen in linking plant phenotypes to reproductive fitness. [ABSTRACT FROM AUTHOR]

Abstract Ongoing climatic changes have altered growing conditions for plants by limiting water availability and inducing unprecedented temperature increases, eliciting plant functional responses that compromise floral trait expression, reduce pollen production and promote early self‐pollination. In a controlled greenhouse study, plants of Collinsia heterophylla, an annual mixed‐mated hermaphrodite, were grown under temperature and water stresses. Floral trait responses and related effects on plant reproductive success were recorded. Plants grown under temperature and water stresses were shorter and had fewer leaves at flowering than control plants. Temperature‐stressed plants flowered earlier and had smaller flowers that produced fewer per capita pollen grains than control and water‐stressed plants. While lifetime flower production in plants experiencing temperature stress alone or water stress alone was similar to control plants, those receiving combined temperature and water stresses had significantly lower lifetime flower production. Abiotic stress did not affect investment in female traits such as ovule number per flower, but impacted male traits seen as fewer pollen grains per flower. In plants experiencing abiotic stress, an increase in autonomous self‐pollination was facilitated through a compromise in herkogamy, a sexual interference mechanism that promotes cross‐pollination. Spatial separation between stigma and anther, a measure of herkogamy was zero or negative in stressed plants. Thus, abiotic stress responses in plants did not compromise plant reproductive success as autonomous selfing was augmented. In nature, such responses will likely reduce available nutrition for pollinators through decreased flower and pollen production.

Many methods have been devised to count pollen grains automatically; however, few combine speed, reliability, inexpensiveness and user friendliness. This study describes a combination of simple, glycerine-based extraction, digital imaging and free particle counting software configured to achieve semi-automated processing of a large volume of images. Pollen grains were extracted from anthers of 10 common perennial grass (Poaceae) species, all implicated in pollinosis in Europe, and samples, illuminated on slides and digitally imaged. ImageJ algorithms were designed to remove significant extraneous content and count just the pollen grains, then applied in batch mode on multiple images. Accuracy was assessed by comparing a sample of automated software counts to manual, visual counts of the same images and found to be high. Total pollen production per anther and per inflorescence was estimated by counting the number of pollen grains per anther and the number of florets per inflorescence. Methodological and natural variation in pollen counts is discussed. Results were compared to published pollen counts of the same species; new pollen production figures are published for Cynosurus cristatus. This method is portable to other plant species, and requires only readily available reagents, equipment and software, it is quick, reliable, inexpensive and user friendly. [ABSTRACT FROM AUTHOR]

In plants, the timely degeneration of tapetal cells is essential for providing nutrients and other substances to support pollen development. Rapid alkalinization factors (RALFs) are small, cysteine-rich peptides known to be involved in various aspects of plant development and growth, as well as defense against biotic and abiotic stresses. However, the functions of most of them remain unknown, while no RALF has been reported to involve tapetum degeneration. In this study, we demonstrated that a novel cysteine-rich peptide, EaF82, isolated from shy-flowering ‘Golden Pothos’ (Epipremnum aureum) plants, is a RALF-like peptide and displays alkalinizing activity. Its heterologous expression in Arabidopsis delayed tapetum degeneration and reduced pollen production and seed yields. RNAseq, RT-qPCR, and biochemical analyses showed that overexpression of EaF82 downregulated a group of genes involved in pH changes, cell wall modifications, tapetum degeneration, and pollen maturation, as well as seven endogenous Arabidopsis RALF genes, and decreased proteasome activity and ATP levels. Yeast two-hybrid screening identified AKIN10, a subunit of energy-sensing SnRK1 kinase, as its interacting partner. Our study reveals a possible regulatory role for RALF peptide in tapetum degeneration and suggests that EaF82 action may be mediated through AKIN10 leading to the alteration of transcriptome and energy metabolism, thereby causing ATP deficiency and impairing pollen development.

The aim of this study was the evaluation of date palm (Phoenix dactylifera L.) pollen production during the 2021 and 2022 seasons in the Mexicali Valley, Mexico. Twelve seed-propagated male palms of 20 years of age and similar vigor were selected and grouped into four groups with phenotypic characteristics of the common female cultivars in the area (Medjool, Deglet Noor, Khadrawy, and Zahidi). The pollen was extracted manually, with average production among all individuals of 780.94 and 777.11 g, in 26 and 24 inflorescences, respectively, for each year. Likewise, the flowering period on average was 47 and 41 days for each year. The pollen extracted from the earliest four inflorescences averaged 38.7 and 32.55 g, while that of the latest one produced 10.70 g and 18.28 g for each year, respectively. Seedling male palms with a phenotype similar to the Deglet Noor cultivar produced the greatest amount of pollen with 1250.98 and 1114.26 g on average for each year, produced during a late, short flowering period. Likewise, those palms with phenotypes similar to the Medjool cultivar produced the second-highest amount of pollen with 851.28 and 866.43 g on average for each year, produced during an early, long flowering period. Finally, an in vivo viability test through the fruit set percentage, revealed that the use of any of these four pollen sources would be suitable for the pollination of the recipient female cultivar Medjool, the most widely cultivated variety in Mexico. These results will allow date producers to select and propagate better pollen-producing male palms. [ABSTRACT FROM AUTHOR]

Mediterranean forests dominated by Quercus species are of great ecological and economic value. The Quercus pollen season, peaking in April, varies in concentration due to geographical and climatic factors and has a remarkable allergenic potential. This study investigates Quercus trends in the Alentejo region of Portugal and examines the influence of meteorological parameters on DPC, PSD and SPIn, as well as the impact on allergic respiratory disease. The results show a progressive increase in Quercus Forest area from 1995 to 2018. Temperature and Precipitation are a key factor influencing pollen concentration, especially before peak of pollen season and prior to the pollen season. Particularly prior to the season, the precipitation of t-6 before influence, significantly, the pollen production. On the other hand, Global Srad and RH determine the beginning of the season. Using quartile-based categorization and multivariate statistical analysis, we identified years and scenarios within the IPCC projections where meteorological conditions influence may SPIn production. The study found a statistically significant correlation between high Quercus pollen concentrations in April and increased antihistamine sales. These findings are crucial for enhancing pollen forecast models and early warning systems. [Display omitted] • The role of weather condition previous and during the allergenic Quercus season was investigated. • Statistical Analysis was performed on pollen and weather factors for 17 years, in Évora city. • Meteorological parameters play a key role determining the pollen production, dynamics and start Quercus season. • Significant impact of Quercus genus in allergic disease. • Climate change may impact human exposure to this allergen, thus impacting future pollen allergy map. [ABSTRACT FROM AUTHOR]

Aim: Plant reliance on animal mutualists is expected to decrease with latitude owing to increasing environmental instability. As a consequence, more erratic animal pollination in the temperate zones than in the tropics could translate into lower efficiency in pollen transfer, and thus increasing pollen wastage. Despite the relevance of this hypothesis for plant reproductive evolution, the implications of a proposed latitudinal gradient in pollinator reliability for pollen and ovule production, traits directly affecting seed siring and seed set, respectively, remain unresolved. Location: Global. Time period: 1971–2020. Major taxa studied: Angiospermae. Methods: Based on a bibliographic survey and our own data, we collated a dataset with information on pollen production (P) and ovule number (O) per flower from 419 studies, including a total of 1,392 animal‐pollinated angiosperm species from 141 families distributed worldwide and sampled between the equator and 68.35° latitude. Using phylogenetic general linear mixed models, we investigated latitudinal variation in P and O. We also tested a latitudinal effect on several ancillary plant traits associated with a plant's mating system and pollinator specialization that might confound any latitudinal effect on gamete production. Results: P but not O was positively associated with latitude, a trend that even became stronger after including the latitudinally varying ancillary traits (i.e., growth form, flower size, flower symmetry and number of pollinator orders). The latitudinal effect on P was more pronounced among species producing large flowers, a trait that could be linked to self‐incompatibility and thus outcrossing. A weak phylogenetic patterning of P also indicates high evolvability potential of this trait, which may have an effect on both male and female plant fitness. Main conclusions: Even though a latitudinal trend in pollinator reliability still awaits direct testing, the observed latitudinal increase in P across angiosperms can be interpreted as an evolutionary consequence of an increasingly unpredictable pollination environment. [ABSTRACT FROM AUTHOR]

Pollination success of animal-pollinated flowers depends on rate of pollinator visits and on pollen deposition per visit, both of which should vary with the pollen and nectar "neighborhoods" of a plant, i.e., with pollen and nectar availability in nearby plants. One determinant of these neighborhoods is per-flower production of pollen and nectar, which is likely to respond to environmental influences. In this study, we explored environmental effects on pollen and nectar production and on pollination success in order to follow up a surprising result from a previous study: flowers of Ipomopsis aggregata received less pollen in years of high visitation by their hummingbird pollinators. A new analysis of the earlier data indicated that high bird visitation corresponded to drought years. We hypothesized that drought might contribute to the enigmatic prior result if it decreases both nectar and pollen production: in dry years, low nectar availability could cause hummingbirds to visit flowers at a higher rate, and low pollen availability could cause them to deposit less pollen per visit. A greenhouse experiment demonstrated that drought does reduce both pollen and nectar production by I. aggregata flowers. This result was corroborated across 6 yr of variable precipitation and soil moisture in four unmanipulated field populations. In addition, experimental removal of pollen from flowers reduced the pollen received by nearby flowers. We conclude that there is much to learn about how abiotic and biotic environmental drivers jointly affect pollen and nectar production and availability, and how this contributes to pollen and nectar neighborhoods and thus influences pollination success.

Climate change impacts on the structure and function of ecosystems will worsen public health issues like allergic diseases. Birch trees (Betula spp.) are important sources of aeroallergens in Central and Northern Europe. Birches are vulnerable to climate change as these trees are sensitive to increased temperatures and summer droughts. This study aims to examine the effect of climate change on airborne birch pollen concentrations in Central Europe using Bavaria in Southern Germany as a case study. Pollen data from 28 monitoring stations in Bavaria were used in this study, with time series of up 30 years long. An integrative approach was used to model airborne birch pollen concentrations taking into account drivers influencing birch tree abundance and birch pollen production and projections made according to different climate change and socioeconomic scenarios. Birch tree abundance is projected to decrease in parts of Bavaria at different rates, depending on the climate scenario, particularly in current centres of the species distribution. Climate change is expected to result in initial increases in pollen load but, due to the reduction in birch trees, the amount of airborne birch pollen will decrease at lower altitudes. Conversely, higher altitude areas will experience expansions in birch tree distribution and subsequent increases in airborne birch pollen in the future. Even considering restrictions for migration rates, increases in pollen load are likely in Southwestern areas, where positive trends have already been detected during the last three decades. Integrating models for the distribution and abundance of pollen sources and the drivers that control birch pollen production allowed us to model airborne birch pollen concentrations in the future. The magnitude of changes depends on location and climate change scenario. [ABSTRACT FROM AUTHOR]

• The study focuses on 11 major allergenic taxa including Poaceae, Betula, Olea, Artemisia , Urticaceae, Cupressaceae, Alnus, Corylus, Platanus, Morus , and Fraxinus. • vast majority of studies have been conducted in Europe, particularly in southern Europe. • Alnus has a positive trend in APIn and a consistent increase in pollen concentrations from 1974 to 2020. • Accumulated rainfall and mean air temperature during flowering and preceding months exhibit different relationships with APIn. • Betula and Cupressaceae, exhibit a negative correlation between API and mean air temperature during the flowering period. • Changes in temperature and rainfall highly impact the flowering conditions and seasonal pollen concentration of anemophilous Mediterranean species. Climate change has been identified as a major driver of alterations in pollen production, with potential implications for allergenic diseases and ecosystems. This systematic review and meta-analysis examine the impacts of global warming on the Annual Pollen Integral (APIn), a measure of pollen production, across multiple plant species. We conducted a comprehensive literature review and selected studies based on predetermined inclusion criteria. Our analysis covered 11 major allergenic taxa (Poaceae, Betula, Olea, Artemisia , Urticaceae, Cupressaceae, Alnus, Corylus, Platanus, Morus , and Fraxinus), with a focus on long-term trends in the relationship between temperature and APIn. The results revealed a generalized increase in APIn over the study period (1974–2020) for most taxa. Notable exceptions were Urticaceae and Artemisia , which exhibited a generalized decrease. Our analysis also highlighted a varying start and end years for the time series studies, ranging from 1974 in the United Kingdom to 2020. The earliest series were from Belgium, Italy, and the UK, while the most numerous studies were from Spain and Poland. Subsequent analysis of the impact of environmental parameters on APIn revealed complex patterns. Accumulated rainfall and mean air temperature during flowering and preceding months exhibited different relationships with APIn depending on the taxa and the period considered. These findings underscore the complex impacts of climate change on pollen production, with significant variations across different plant species and regions. [ABSTRACT FROM AUTHOR]

The aim of this study was the evaluation of date palm (Phoenix dactylifera L.) pollen production during the 2021 and 2022 seasons in the Mexicali Valley, Mexico. Twelve seed-propagated male palms of 20 years of age and similar vigor were selected and grouped into four groups with phenotypic characteristics of the common female cultivars in the area (Medjool, Deglet Noor, Khadrawy, and Zahidi). The pollen was extracted manually, with average production among all individuals of 780.94 and 777.11 g, in 26 and 24 inflorescences, respectively, for each year. Likewise, the flowering period on average was 47 and 41 days for each year. The pollen extracted from the earliest four inflorescences averaged 38.7 and 32.55 g, while that of the latest one produced 10.70 g and 18.28 g for each year, respectively. Seedling male palms with a phenotype similar to the Deglet Noor cultivar produced the greatest amount of pollen with 1250.98 and 1114.26 g on average for each year, produced during a late, short flowering period. Likewise, those palms with phenotypes similar to the Medjool cultivar produced the second-highest amount of pollen with 851.28 and 866.43 g on average for each year, produced during an early, long flowering period. Finally, an in vivo viability test through the fruit set percentage, revealed that the use of any of these four pollen sources would be suitable for the pollination of the recipient female cultivar Medjool, the most widely cultivated variety in Mexico. These results will allow date producers to select and propagate better pollen-producing male palms.

Mosaic structure of urban green areas is regarded as favorable for pollinating insects. Ornamental plants can provide food resources to pollinators and may thus be used to create pollinator-friendly habitats. However, detailed data on forage quantity and quality is required for the selection of the most valuable plant species. In this paper, blooming biology, pollen production, and insect visitors of two forms (blue-flower and white-flower) of Polemonium caeruleum were studied in the period of 2012–2014 in Lublin, SE Poland. Both forms bloomed from mid-May until mid-June. The average mass of pollen produced in a single flower was 1.57 mg and 1.39 mg in blue-flower and white-flower forms, respectively. On average, the blue-flower form produced 7.74 g of pollen/m2, while the white-flower form yielded 6.54 g of pollen/m2. Both forms attracted mainly honey bees and solitary bees. Polemonium caeruleum can be considered a good source of pollen for honey bees and wild insect pollinators and should be propagated in urban pollinator-friendly arrangements.

The knowledge of nectar secretion and pollen production is important for understanding the biology of invasive species. In the present paper, the floral reward in Solidago canadensis and S. gigantea (Asteraceae), two invasive plant species in Europe, were investigated. Flowers of Solidago species are protandrous. The floral nectar was found to be rich in hexose (sucrose/fructose/glucose – 13.8/32.7/53.5% in S. canadensis and 18.3/35.1/46.6% in S. gigantea). The per-flower rewards (sugars/pollen) in the Solidago species were not abundant; however, due to the formation of dense populations and massive floral display, high amounts of resources were produced at the community level. The mean sugar output was 482.3 kg/ha in S. canadensis and 121.6 kg/ha in S. gigantea. The mean pollen yield was 30.7 kg/ha (S. canadensis) and 6.5 kg/ha (S. gigantea). In the landscape with limited floral resources, the nectar and pollen available in Solidago flowers are important and can provide additional (or even exclusive) food resources for pollinators during summer/late summer. In particular, areas invaded by Solidago species may be attractive to beekeepers, as >80.0% of visits were performed by Apis mellifera. However, a broad spectrum of wild insect visitors (including Bombus spp., Vespula spp., Diptera, Lepidoptera, Coleoptera) deserves further studies to assess the impact of mass flowering in Solidago species on the native plant species-insect interactions. [ABSTRACT FROM AUTHOR]

This study is related to an overall analysis of the most relevant pollen season modifications as they emerge from the aerobiological monitoring activity in the network of stations in Emilia-Romagna, a region located in Northern Italy. The taxa selected for the study are among the most important from an allergenic point of view. The selected period goes from 1991 to 2017 in order to have a similar length for all the different taxa in all the stations, regardless of their date of activation. Statistical analysis of the time series of some pollen season indicators has been carried out in the period, with the aim of pointing out the most relevant changes in the ensemble of the monitoring stations. The available database lasting more than 25 years can be the basis for a robust statistical analysis of the long-term trends in the time series of pollen seasonal indicators. The stations are operating throughout the whole Emilia-Romagna territory, spanning a range of climatic conditions from the inner Po Valley to the coastal area. Results of the trend analysis indicate that the starting and the peak dates of the pollen season are in prevalent advance. This is true both for most herbaceous taxa, as well as for several arboreal ones. As for pollen production, a different behaviour characterizes herbaceous and arboreal taxa; in fact, a generally decreasing trend interests all herbaceous taxa, while a prevalent increasing trend is present in several of the latter. Pollen season indicators are certainly more directly affected by the changes associated with the meteo-climatic forcing and are possibly more influenced by climatic change. [ABSTRACT FROM AUTHOR]

Premise: Variation in pollen‐ovule ratios is thought to reflect the degree of pollen transfer efficiency—the more efficient the process, the fewer pollen grains needed. Few studies have directly examined the relationship between pollen‐ovule ratio and pollen transfer efficiency. For active pollination in the pollination brood mutualisms of yuccas and yucca moths, figs and fig wasps, senita and senita moths, and leafflowers and leafflower moths, pollinators purposefully collect pollen and place it directly on the stigmatic surface of conspecific flowers. The tight coupling of insect reproductive interests with pollination of the flowers in which larvae develop ensures that pollination is highly efficient. Methods: We used the multiple evolutionary transitions between passive pollination and more efficient active pollination to test if increased pollen transfer efficiency leads to reduced pollen‐ovule ratios. We collected pollen and ovule data from a suite of plant species from each of the pollination brood mutualisms and used phylogenetically controlled tests and sister‐group comparisons to examine whether the shift to active pollination resulted in reduced pollen‐ovule ratios. Results: Across all transitions between passive and active pollination in plants, actively pollinated plants had significantly lower pollen‐ovule ratios than closely related passively pollinated taxa. Phylogenetically corrected comparisons demonstrated that actively pollinated plant species had an average 76% reduction in the pollen‐ovule ratio. Conclusions: The results for active pollination systems support the general utility of pollen‐ovule ratios as indicators of pollination efficiency and the central importance of pollen transfer efficiency in the evolution of pollen‐ovule ratio. [ABSTRACT FROM AUTHOR]

Mosaic structure of urban green areas is regarded as favorable for pollinating insects. Ornamental plants can provide food resources to pollinators and may thus be used to create pollinator-friendly habitats. However, detailed data on forage quantity and quality is required for the selection of the most valuable plant species. In this paper, blooming biology, pollen production, and insect visitors of two forms (blue-flower and white-flower) of Polemonium caeruleum were studied in the period of 2012-2014 in Lublin, SE Poland. Both forms bloomed from mid-May until mid-June. The average mass of pollen produced in a single flower was 1.57 mg and 1.39 mg in blue-flower and white-flower forms, respectively. On average, the blue-flower form produced 7.74 g of pollen/m², while the white-flower form yielded 6.54 g of pollen/m2. Both forms attracted mainly honey bees and solitary bees. Polemonium caeruleum can be considered a good source of pollen for honey bees and wild insect pollinators and should be propagated in urban pollinator-friendly arrangements. [ABSTRACT FROM AUTHOR]

The reproductive biology of Cornus capitata was studied in detail from June 2014 to October 2015 in Tehri Garhwal, Uttarakhand, western Himalaya, India and elucidated floral morphology, confirming autogamy, geitonogamy, and xenogamy. A new inflorescence ball formed each year with developing fruits that were initiated the previous year; thus reproduction is a continuous cycle. The total pollen production within a tree ranged between 4.0 × 107 and 9.3 × 107. Anthesis peaked between 08:00 and 10:00. There was significant effect of micro-environmental condition on anthesis (F = 243.8, p = 3.01). A significant positive relationship between the number of lateral shoots and total inflorescence showed that the inflorescence production in C. capitate depends largely on the number of lateral shoots. Time and concentration of various solutions significantly affected pollen germination (time: F = 5.39, p = 0.002; concentration: F = 1.40, p = 0.234). Anthophora bees and thrips were observed as the main pollinators. There was a significant difference in seed set between natural and obligate self-pollination (t = 11.84, p = 1.99). Significant effect was also observed on fruit size (t = 8.88, p = 2.09) between open and shaded conditions. SEM micrographs of pollen grains showed that the shape of dehydrated pollen grains differed greatly due to variations in the rate of dehydration among pollen grains within the anther. Seed germination was observed only in quality seed derived from open pollination, supporting xenogamy in C. capitata. Findings of the present study will be of immense value in formulating effective conservation measures for the species in wild habitats. [ABSTRACT FROM AUTHOR]

Most apple trees (Malus domestica Borkh.) are self-incompatible and fruit yield depends on cross-pollination between genetically compatible cultivars with synchronous flowering. Flowering intensity can vary strongly among years due to the biennial bearing habit of the cultivars. The knowledge of the phenological stages and floral and pollen characteristics is essential to select suitable pollen donors. We evaluated the phenotypic variability of flowering-related traits (i.e., flowering phenology, flowering intensity, pollen production and pollen quality) in 45 apple cultivars over two successive flowering seasons. Large phenotypic variability was found among the studied cultivars indicating that the local germplasm collection provides a good source of genetic and phenotypic diversity. However, low correlations were observed between floral biology traits and, consequently, the improvement in one trait seems not to affect other traits. Some of the cultivars such as ‘Perurico’ and ‘Raxila Dulce’ regularly produced copious amounts of high-quality pollen which can improve the pollen load dispersion leading to a most effective pollination process. We did not identify statistically significant correlations between pollen attributes and the biennial bearing phenomenon. The large variation in bloom dates from year-to-year observed under a typical Oceanic climate makes it advisable to combine cultivars in new plantings.

Offering more floral resources for urban bees can be achieved by growing ornamental bee plants. The aim of the present study was to evaluate selected Asteraceae (Calendula officinalis ‘Persimmon Beauty’ and ‘Santana’, Centaurea macrocephala, Cosmos sulphureus, Dahlia pinnata, Tagetes patula, Tithonia rotundifolia, and Zinnia elegans) as pollen sources for pollinators. Under urban conditions in Lublin, SE Poland, the investigated plants flowered from late June to the end of October. The mass of pollen produced in florets and capitula was found to be species-related. The highest pollen amounts per 10 florets (10.1 mg) as well as per capitulum (249.7 mg) were found for C. macrocephala. The mass of pollen yielded by a single plant depended on both the pollen mass delivered per disk florets and the proportion of disk florets in capitulum, and the flowering abundance of the plants. A single plant of D. pinnata and a single plant of T. rotundifolia each produced the largest pollen mass. Mean pollen yield per 1m2 of a plot ranged from 6.2 g (Z. elegans) to 60.7 g (D. pinnata). Pollen grains are tricolporate, with echinate exine, medium or small in size. They can be categorised as oblatespherical, spherical, and prolatespherical. The principal visitors to C. macrocephala, C. sulphureus, and C. officinalis were honey bees, whereas bumble bees dominated on T. rotundifolia and D. pinnata. A magnet plant for butterflies was Z. elegans. Among the investigated species, D. pinnata, C. macrocephala, and T. rotundifolia were found to be the most valuable sources of pollen flow for managed and wild bees.

Colchicine is widely used as a mutagen to induce production of diploid gametes in plants. However, whether colchicine affects induced pollen viability remains unclear. To clarify whether colchicine affected the viability of induced pollen, we induced production of diploid pollen by colchicine, followed by pollen germination in vitro and crossing induced pollen with normal gametes to produce triploid in Populus tomentosa Carrière. The results showed that the predominant meiotic stages and the number of colchicine injections had significant effects on the occurrence rates of induced 2n pollen. When the colchicine injection was given at diakinesis, a significant decrease in the pollen production per bud was observed (p

Date palm pollen (DPP) plays a very important role in the fertilization process, since its viability and the pollination method influence on the quality, development, and yield of the fruit. In the present study, a broad review of its main characteristics, consumption, and DPP production are presented, as well as a description of its extraction methods and viability tests. The evolution of the pollination methods used in the date palm is also presented, from its natural pollination to the use of specialized mechanical and electrical devices, as well as the use of dry DPP and the current trend towards the use of DPP in liquid suspension. Likewise, the efficiency of the methods of natural pollination (wind); traditional (strands placement); dusting hand; dusting with manual, mechanical, or electric pollinator; and liquid pollination were evaluated from the fruit set percentage (FSP). Finally, starting from a scientometric analysis, the pollination methods were widely discussed, concluding that the dusting spraying of pollen suspension with liquid DPP is the pollination method that commonly presents the highest FSP, followed by dusting dry DPP with a motorized pollinator.

This research was conducted to investigate rootstock effects on seed yield and quality in watermelon. The work was conducted in the experimental fields and laboratories of the Department of Horticulture of the University of Cukurova in the 2016 and 2017 growing seasons. Watermelon cv. Crimson sweet (CS) scion was grafted onto three different rootstocks (Cucurbita 'NUN-9075', Lagenaria 'Argentario', and citron watermelon 'PI296341'). Plants were assessed according to their main stem length, main stem diameter, number of nodes, biomass, pollen production and development, fruit yield and quality, and seed yield and quality. NUN-9075/CS and Argentario/CS graft combinations resulted in higher average stem length, plant biomass, fruit yield and quality, seed yield, seed emergence, and germination percentage. There was no significant difference observed between graft combinations in pollen viability, pollen germination, and normal pollen production. No significant difference was observed between graft combinations in accelerated ageing (AA), and the seed germination decreased after AA of 192 h. In the second year (2017), there was higher main stem length, main stem diameter, total fruit yield, seed yield, and number of seeds per fruit compared to the first year (2016). Based on the results of this study, NUN-9075 rootstock performed better than other rootstocks; hence, it is recommended as the best rootstock. [ABSTRACT FROM AUTHOR]

The influence of the climatic factors on the honey-producing potential of courgettes Cucurbita pepo var. giromontia was studied within the framework of the project "Investigation of the impact of biochar on soil fertility and agricultural crops development". By conducting fi eld experiments, the influence of abiotic factors (temperature, air humidity and rainfall) on the development of the plants was studied. The amount of nectar and pollen and the visit of the bees to the plants were determined. Incorporation of biochar in soil has generally been shown to be beneficial for growing crops. [ABSTRACT FROM AUTHOR]

Chromosome doubling of maize haploids is a bottleneck in the large-scale application of doubled haploid (DH) technology. Spontaneous chromosome doubling (SCD) of haploid has been taken as an important method in the production of DH lines and low haploid male fertility (HMF) is a main limiting factor for the use of SCD. To study its genetic basis, haploids of 119 DH lines derived from a cross between inbred lines Qi319 and Chang7-2 were used to map the quantitative trait locus (QTL) contributing to HMF. Three traits including anther emergence rate (AER), anther emergence score (AES) and pollen production score (PPS) of the haploid population were evaluated at two locations. The heritability of the three traits ranged from 0.70 to 0.81. The QTL contributing to AER, AES and PPS were identified on the chromosomes 1, 2, 3, 4, 5, 7, 9 and 10. Five major QTL, qAER5-1, qAER5-2, qAES3, qPPS1 and qPPS5, were found and each could explain more than 15% of the phenotypic variance at least in one environment. Two major QTL, qPPS1 and qPPS5, and two minor QTL, qAES2 and qAER3, were repeatedly detected at both locations. To increase the application efficiency of HMF in breeding programs, genomic prediction for the three traits were carried out with ridge regression best linear unbiased prediction (rrBLUP) and rrBLUP adding QTL effects (rrBLUP-QTL). The prediction accuracies of rrBLUP-QTL were significantly higher than that by rrBLUP for three traits (p < 0.001), which indirectly indicates these QTL were effective. The prediction accuracies for PPS were 0.604 (rrBLUP) and 0.703 (rrBLUP-QTL) across both locations, which were higher than that of AER and AES. Overall, this study provides important information to understand the genetic architecture of SCD of maize haploids.

Natural forests are considered a reservoir of great biological diversity constituting one of the most important ecosystems in Europe. Quercus study is essential to assess ecological conservation of forests, and also of economic importance for different industries. In addition, oak pollen can cause high sensitization rates of respiratory allergies in pollen-allergy sufferers. This study sought to know the pollen production of six oak species in the transitional area between the Eurosiberian and Mediterranean Bioclimatic Regions, and to assess the impact of climate change on airborne oak pollen concentrations. The study was conducted in Ourense (NW Spain) over the 1993–2019 period. A Lanzoni VPPS 2000 volumetric trap monitored airborne pollen. A pollen production study was carried out in ten trees randomly selected in several Quercus forest around the Ourense city. Oak pollen represented around 14% of annual total pollen registered in the atmosphere of Ourense, showing an increasing trend during the last decade. Pollen production of the six studied oak species follow the proportions 1:1:2:5:90:276 for Q. ilex, Q. faginea, Q. rubra, Q. suber, Q. pyrenaica, and Q. robur respectively. We detected a significant trend to the increase of the annual maximum temperature, whereas a decrease of the maximum and mean temperatures during three previous months to oak flowering. This could be related with the detected trend to a delay of the oak Main Pollen Season onset of 0.47 days per year. We also found significant trends to an increase of the annual pollen integral of 7.9% pollen grains per year, and the pollen peak concentration of 7.5% pollen grains per year. Quercus airborne pollen monitoring as well as the knowledge of the reproductive behavior of the main oak species, bring us an important support tool offering a promising bio-indicator to detect ecological variations induced by climate change.

Given the rise in the global population and the consequently high levels of pollution, urban green areas, such as those that include plants in the Cupressaceae family, are suitable to reduce the pollution levels, improving the air quality. However, some species with ornamental value are also very allergenic species whose planting should be regulated and their pollen production reduced by suitable pruning. The Aerobiological Index to create Risk maps for Ornamental Trees (AIROT), in its previous version, already included parameters that other indexes did not consider, such as the width of the streets, the height of buildings and the geographical characteristics of cities. It can be considered by working with LiDAR (Light Detection and Ranging) data from five urban areas, which were used to create the DEM and DSM (digital elevation and surface models) needed to create one of the parameters. Pollen production is proposed as a parameter (α) based on characteristics and uses in the forms of hedges or trees that will be incorporated into the index. It will allow the comparison of different species for the evaluation of the pruning effect when aerobiological risks are established. The maps for some species of Cupressaceae (Cupressus arizonica, Cupressus macrocarpa, Cupressus sempervirens, Cupressocyparis leylandii and Platycladus orientalis) generated in a GIS (geographic information system) from the study of several functions of Kriging, have been used in cities to identify aerobiological risks in areas of tourist and gastronomic interest. Thus, allergy patients can make decisions about the places to visit depending on the levels of risk near those areas. The AIROT index provides valuable information for allergy patients, tourists, urban planning councillors and restaurant owners in order to structure the vegetation, as well as planning tourism according to the surrounding environmental risks and reducing the aerobiological risk of certain areas.

The availability of pollen in sorghum (Sorghum bicolor [Moench] L.) production is generally not considered a restrictive factor due to the sorghum self-pollination process. However, during the cross pollination process restrictions could play a role that depends on the distance of the pollen source, the proportion of male to female plants and the sowing date. The objective of this experiment was to establish the relationship between pollen production, deposition and season variations in seed set under different proportion male:female rows. The A9/B9-line was sowed on May 3, June 10, 2005, with the proportions: 2:4, 2:6 andon April 3, 2006 with proportions of 2:12 and 2:16 in Montecillo, State of Mexico. In isolines, number of flowers per panicle was measured at the ending of flowering. During all the flowering period, pollen production was quantified in male line and pollen deposition on female line rows using passive traps. During harvest the length of panicle was measured, quantified by the number of seeds per panicle and seed set was estimated. The pollen availability, synchrony floral, duration of phenological stage and seed production were influenced by sowing date and varied with the male and female rows. Precocity was observed in A9 female isoline more than B9-male line in three sowing dates. Number of pollen grains and seeds declined proportionally with increasing distance from the pollen source, but the rate was different for each proportion. The pollination was associated more to the size of pollen source and its dispersion than with population of female plants.

The flowering phenology and pollen production of three ornamental Centaurea species were investigated in the years 2009 and 2012-2013. The study objects, Centaurea montana L. = Cyanus montanus (L.) Hill, Centaurea mollis Waldst & Kit, and Centaurea dealbata Willd. were cultivated within an area of the UMCS Botanical Garden in Lublin, Poland (51° 14’ N, 22° 34’ E). Under the environmental conditions of SE Poland, the Centaurea species flowered continuously from mid-May to the first week of June. The mass of pollen in anthers was found to be species-related: 3.70 mg (C. montana), 4.02 mg (C. mollis), and 6.01 mg (C. dealbata) per 100 anthers. The total pollen yield was related to the mass of pollen produced in flowers and the abundance of blooming. Pollen grains were medium-sized, spheroid (C. dealbata) or prolato-spheroid (C. mollis and C. montana) in shape, and characterized by high viability (over 80% on average). The pollen provided by the plants of ornamental Centaurea species amounted to 6.0 - 7.9 g per m2 on average. The honeybee was the most frequent visitor of C. dealbata, accounting for 55.2% of the total pollinators, and bumblebee species predominated on the flowers of both C. montana (77.7%) and C. mollis (85.6%). Solitary bees and dipterans were also observed on the flowers of all species studied, but C. mollis was avoided by lepidopterans. Ornamental Centaurea species provide pollen reserves that could support communities of invertebrate pollinators, although the period of effective supply fluctuates annually due to changeable periods of blooming.

Oak pollen is a major respiratory allergen in Korea, and the distribution of oak trees is expected to increase by ecological succession and climate change. One of the drivers of climate change is increasing CO2, which is also known to amplify the allergy risk of weed pollen by inducing elevated allergenic protein content. However, the impact of CO2 concentration on tree pollen is not clearly understood due to the experimental difficulties in carrying out extended CO2 treatment. To study the response of pollen production of sawtooth oak trees (Quercus acutissima) to elevated levels of ambient CO2, three open-top chambers at the National Institute of Forest Science in Suwon, Korea were utilized with daytime (8 am-6 pm) CO2 concentrations of ambient (× 1.0, ~ 400 ppm), × 1.4 (~ 560 ppm), and × 1.8 (~ 720 ppm) treatments. Each chamber had three sawtooth oak trees planted in September 2009. One or two trees per chamber matured to bloom in 2016. Five to six catkins were selected per tree and polyethylene bags were attached to collect pollen grains. The total number of catkins per tree was counted and the number and weight of pollen grains per catkin were measured. Oak allergen—Que a 1 (Allergon Co., Uppsala, Sweden)—was extracted and purified to make an ELISA kit by which the antigen levels in the pollen samples were quantified. Total pollen counts per tree of the × 1.4 and × 1.8 treatments showed significant increase of 353 and 1299%, respectively, from the × 1.0 treatment (p < 0.001). Allergenic protein contents at the × 1.4 and × 1.8 treatments also showed significant increase of 12 and 11%, respectively (p = 0.011). The × 1.8 treatment induced significant difference from the × 1.0 treatment in terms of pollen production and allergenic protein content, whereas the × 1.4 treatment showed mixed significance. In summary, the oak trees under the elevated CO2 levels, which are expected in the changing climate, produced significantly higher amount of pollen and allergenic protein than under the present air conditions. [ABSTRACT FROM AUTHOR]

Abstract: Honey bees require nectar and pollen from flowers: nectar for energy and pollen for growth. The demand for nectar and pollen varies during the year, with more pollen needed in spring for colony population growth and more nectar needed in summer to sustain the maximum colony size and collect surplus nectar stores for winter. Sufficient bee forage is therefore necessary to ensure a healthy bee colony. Land‐use changes can reduce the availability of floral resources suitable for bees, thereby increasing the susceptibility of bees to other stressors such as disease and pesticides. In contrast, land‐based management decisions to protect or plant bee forage can enhance pollen and nectar supply to bees while meeting other goals such as riparian planting for water‐quality improvement. Commercial demand for honey can also put pressure on floral resources through over‐crowding of hives. To help understand and manage floral resources for bees, we developed a spatial model for mapping monthly nectar and pollen production from maps of land cover. Based on monthly estimated production data we mapped potential monthly supply of nectar and pollen to a given apiary location in the landscape. This is done by summing the total production within the foraging range of the apiary while subtracting the estimated nectar converted to energy for collection. Ratios of estimated supply over theoretical hive demand may then be used to infer a potential landscape carrying capacity to sustain hives. This model framework is quantitative and spatial, utilizing estimated flight energy costs for nectar foraging. It can contribute to management decisions such as where apiaries could be placed in the landscape depending on floral resources and where nectar limited areas may be located. It can contribute to planning areas for bee protection or planting such as in riparian vegetation. This would aid managed bee health, wild pollinator protection, and honey production. We demonstrate the methods in a case study in New Zealand where there is a growing demand for mānuka (Leptospermum scoparium) honey production. [ABSTRACT FROM AUTHOR]

Abstract: Natural alloplasmic cytoplasmic male sterile (CMS) clones of industrial chicory were obtained after crossing wild chicory with selected breeding lines. We investigated the CMS stability of 10 clones in various environmental growing conditions. CMS was stable under cool growing conditions in most of them. Fertility restoration, based on pollen production scores, was observed in all clones after a period of hot temperatures. The early flower bud stage was sensitive, resulting in fertile flowers 12–17 days after exposure to high temperatures. Experiments under controlled growing conditions at 15°C demonstrated that a heat shock of 2 days at 25 or 30°C was sufficient to restore fertility. Sterile flowers were formed when plants were again grown at lower temperatures. Significant differences between individual clones were observed, indicating the potential of genetic selection to obtain stable CMS parent lines. [ABSTRACT FROM AUTHOR]

The development of novel antimicrobial drugs, as well as the discovery of novel compounds able to promote honeybee’s growth, represents major challenges for modern entomology. The main aim of this study was to investigate whether Brevibacillus laterosporus isolated from the digestive tract of Saudi honeybees, Apis mellifera, was able to stimulate colony strength parameters of honeybees and to evaluate its ability to produce antimicrobial agents. Honeybees were collected in Dirab, Riyadh Region, Saudi Arabia, and microorganisms were isolated and identified by 16S ribosomal RNA analysis. Microscopic identification of the microorganism in its native state was facilitated by atomic force microscopy at high-resolution imaging. Active biological compounds were produced by submerged fermentation with B. laterosporus. The fermented broth was subjected to extraction and purification, and then semi-pure compounds were analyzed by gas chromatography-mass spectrometry. The effectiveness of the crude extract and semi-pure compounds as antimicrobial agents was evaluated by susceptibility assays. More than 22% of the microorganisms isolated from the digestive tract of healthy honeybees have been identified as B. laterosporus, this kind of species has a unique shape and morphological structure. The cyclic dipeptide cyclo(Leu-Pro) produced by B. laterosporus showed biological activity against several pathogenic microorganisms. Furthermore, the total counts of workers, closed brood, and open brood, as well as the production of bee pollen and honey, were better in honeybees treated with a B. laterosporus suspension. The data indicated that the B. laterosporus strain isolated from a healthy honeybee might be a novel probiotic and a producer of important biological compounds. [ABSTRACT FROM AUTHOR]

Grass pollen is the main cause of pollen allergy in Europe, and—given its marked allergenic potential and elevated airborne concentrations—constitutes a major public health risk. This study sought to identify the grass species triggering allergies during the highest-risk periods, and to measure the contribution of each species to airborne grass pollen concentrations. This type of research is particularly useful with a view to optimising the prevention and diagnosis of pollen allergies and developing the most effective immunological treatments. To that end, a total of 28 species potentially responsible for allergies were analysed. In order to assess the potential contribution of these species to overall airborne pollen concentrations, an index was designed (Pollen Contribution Index) based on the following parameters for each species: flowering phenology, pollen grain size (polar and equatorial axes), abundance of the species in the area and pollen production. The species contributing most to airborne pollen concentrations were, in order: Dactylis glomerata subsp. hispanica , Lolium rigidum , Trisetum paniceum and Arrhenatherum album . These species all shared certain features: small grain size (and thus greater buoyancy in air), high pollen production and considerable abundance. This Index was applied to a case study in a Mediterranean-climate area of the central Iberian Peninsula, but could equally be applied to other areas and other allergenic pollens. Findings showed that a small number of species were responsible for most airborne grass pollen. [ABSTRACT FROM AUTHOR]

Flowering phenology and variation in total pollen production per tree in the natural population of Lagerstroemia speciosa was studied during four successive years, from 2006 to 2009. Reproductive phenophases were highly variable between years and individuals within population. Total flowering period lasts up to three months. Time of maximum anthesis was between 06:00 and 10:00 h of the day. On an average a flower took 2.5 to 3.0 hours for complete opening. Anther dehiscence occurred half an hour after anthesis. Apis spp. and Xylocopa spp. were observed the main pollinators. The visitation rates of pollinators varied from 0.62 to 2.82 visits/flower/hour with the average of 1.68±0.94 visits/flower/hour. Xylocopa bee shows physical fitness with flower morphology, which implies the functional relationship with regard to pollen transfer. There was alternate year production of flowers and pollen grains per tree. In the mass production years, a tree produces 6.4 x 108 and 1.3 x 109 pollen grains, which in poor production years oscillated between 4.2 x 107 and 5.4 x 107. 64% to 80% fruit set following open pollination in mass production year was estimated.

Knowledge of the flowering phase and plant pollination ecology is very important for understanding the life history of long-lived perennials. In the case of rare species, the information may have implications for conservation practices. Our studies on flower morphology and blooming biology of the vulnerable plant Senecio macrophyllus M. BIEB. were conducted in situ (flowering, activity of insect visitors) in the largest population in SE Poland and in laboratory (light and scanning electron microscopy). The disc florets open diurnally with most intensive anthesis in the early afternoon and attract insect visitors with nectar and pollen. In highly protandrous disc florets, pollen viability decreases in time, whereas stigma receptivity increases. The upper part of the pistil forms a brush-like pollen presenter, covered with unicellular trichomes with chromoplasts. Pollen presentation lasts 4–11 hours per floret, and 8 days in a single head, the main function of which is to extend the availability of male gamets for reproduction. The number of florets per head, the head size, and the number of pollen grains produced per anther, and the pollen grain viability differed significantly between microsites. The finding indicates that, apart from the biotic factors, abiotic conditions may considerably influence generative reproduction of the species. In the study area, the principal visitors of S. macrophyllus flowers were Hymenoptera, with predominance of Apis mellifera (53.4% of visits). The remarkable share of butterflies (13.9%) recognized as the long-distance moving insects may improve the genetic variability of individuals within a fragmented population. A more detailed study is necessary to explain the role of insect visitors in effective pollination and in gene transfer between patches. The assessment of optimal conditions for the generative reproduction is fundamental for the in situ conservation of this rare species.

The availability of pollen in sorghum (Sorghum bicolor [Moench] L.) production is generally not considered a restrictive factor due to the sorghum self-pollination process. However, during the cross pollination process restrictions could play a role that depends on the distance of the pollen source, the proportion of male to female plants and the sowing date. The objective of this experiment was to establish the relationship between pollen production, deposition and season variations in seed set under different proportion male:female rows. The A9/B9-line was sowed on May 3, June 10, 2005, with the proportions: 2:4, 2:6 andon April 3, 2006 with proportions of 2:12 and 2:16 in Montecillo, State of Mexico. In isolines, number of flowers per panicle was measured at the ending of flowering. During all the flowering period, pollen production was quantified in male line and pollen deposition on female line rows using passive traps. During harvest the length of panicle was measured, quantified by the number of seeds per panicle and seed set was estimated. The pollen availability, synchrony floral, duration of phenological stage and seed production were influenced by sowing date and varied with the male and female rows. Precocity was observed in A9 female isoline more than B9-male line in three sowing dates. Number of pollen grains and seeds declined proportionally with increasing distance from the pollen source, but the rate was different for each proportion. The pollination was associated more to the size of pollen source and its dispersion than with population of female plants. [ABSTRACT FROM AUTHOR]

Based on a five-year study of pollen production and release in two different natural populations of Mesua ferrea from Indo-Burma region of Northeast India, we determined that pollen output follows a spatio-temporal pattern. Pollen productivity determinations considered various sources of variability, including the number of flowers per branch, flowers per tree, anthers per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and population effects. Anthesis follows a forenoon pattern, whereas anther dehiscence pursues the diurnal pattern. The former was significantly correlated with the timing of floral visitation and pollen deposition on stigmas. The latter, however, had significant relationship with the deposition of pollen grains on microscopic slides. The Apis and Xylocopa bees are the efficient pollinators to achieve the reproductive success in M. ferrea. Annual production of pollen per tree varied from averages of 1.07 ± 0.10 × 10 and 3.24 ± 0.16 × 10 in years of low production, with alternate high years, producing 3.85 ± 0.34 × 10 and 8.22 ± 0.76 × 10 pollen grains per tree. [ABSTRACT FROM AUTHOR]

The estimation of pollen production is widely used in pollination and reproductive ecology, aerobiology and pollen-vegetation relationship studies. Pollen release is the key step in estimating pollen production and therefore, the technique used to release pollen is critical. Three methods, the drying method (DM), mechanical method (MM) and chemical method (CM), are used to determine the amount of pollen released from anthers. Few studies have compared the results obtained from each method, making it difficult to determine which method is most appropriate in a given situation. In this study, we compared existing methods with a new method that increases the amount of pollen released from anthers. Eight species of mangrove trees from the Neilingding-Futian National Nature Reserve were selected for study. We combined the MM and CM to produce a new method (the ultrasonic method, UM). To determine the best ultrasonic treatment time using the UM, different durations were tested and the various responses were analysed. The relationships between pollen rupture and the ultrasonic treatment time, pollen size, exine thickness and aperture size were analysed. Finally, four methods for pollen release from anthers were compared. The results indicated that the UM could be an efficient method to release pollen from the anther. To avoid pollen rupture, ultrasonic treatment times in the UM should be less than 30 s. The pollen rupture rate was significantly correlated with the ultrasonic treatment time (r = 0.618,p < 0.001) and the aperture size (r = 0.248,p = 0.036). This comparative experiment indicated that the UM can generate a greater pollen yield than other methods while causing less pollen rupture than the MM. Therefore, the UM may be suitable for more plant species and more accurate for pollen production estimates than the existing three methods, particularly when estimating pollen production in all community plants. [ABSTRACT FROM PUBLISHER]