Pollen Number Research Articles

Palynotaxonomy of Neotropical species of Paullinia L. (Sapindaceae)

Paullinia is the second-largest genus within the Sapindaceae, with approximately 200 species. It predominantly comprises lianas that inhabit humid forests, mainly the Amazon and Atlantic forests in Brazil. This study aimed to characterize the pollen morphology of 60 species of Paullinia, examining the potential of pollen characters as morphological markers to support the systematics of the genus. The pollen material was obtained from exsiccatae of flower buds from major herbaria. Pollen grains were acetolyzed, measured, described, and illustrated using light microscopy. Scanning electron microscopy was used for accurate descriptions of surface features. The analyzed characters included pollen shape, size, aperture type and number, and exine ornamentation. The similarity of pollen characters between species was analyzed using hierarchical cluster analysis and principal component analysis. The results showed that pollen grains of Paullinia species are shed in monads, heteropolar in most species and isopolar in some others, medium or large in size, oblate or suboblate, and 3- or 3-4-porate, with perforate sexine ornamentation in most species and microreticulate in some others. Multivariate analyses revealed that pollen morphology is informative and holds taxonomic potential, enabling grouping based on the similarity of the unique pollen characters of the genus. Species dispersion on the PCA biplot showed that the five clusters formed by HCA were robust, suggesting that quantitative and qualitative pollen characters exhibit consistency with regard to the similarity species. The palynological findings presented here contribute to enhancing our understanding of the morphological characters, aiding in the taxonomy and systematics of the genus.

Characterization of the floral traits, pollen micromorphology and DNA barcoding of the edible flowers from three basil taxa (Lamiaceae)

AbstractThe edible flowers sector is expanding due to the popularity and uses in culinary recipes of different species. In particular, flowers of Ocimum basilicum L. and related taxa are increasingly used for their aromas and nutritional value. However, there is limited information regarding their morphological characteristics and molecular profiles, which are both important to perform a quality control of food, and to avoid contaminations. Hence, our aim was the study of three basil taxa (O. basilicum ‘Cinnamon’, O. basilicum ‘Blue Spice’, and the hybrid O. × africanum Lour.) to obtain data useful for taxa identification and to understand which traits could be linked to their chemodiversity. The plants were grown in a greenhouse starting from seeds. Flowers were collected at anthesis; the morphology of calyxes, corolla and pollen grains was characterized; DNA barcoding analyses were performed. All taxa were identified only as O. basilicum by molecular analyses, but two haplotypes were distinguishable. All taxa were identifiable due to the presence/absence of specific glandular trichomes, and by pollen size and number of colpi. ‘Cinnamon’ and O. × africanum showed more morphological affinities to each other, but histochemical analyses suggested the separation of the three taxa. Pollen grains from ‘Cinnamon’ had the smallest diameter in polar view and were hexacolpate, while ‘Blue Spice’ pollen showed the highest diameter with grains being hexacolpate/octacolpate, similarly to O. × africanum. Our interdisciplinary study provides the first information for authenticating these basil cultivars in packaged products for human consumption.

Fossil pollen data can reconstruct robust spatial patterns of biodiversity in the past

Fossil pollen data are valuable for understanding past spatio-temporal variations in plant diversity. However, deducing robust patterns of fossil pollen-assemblage properties is challenging due to factors related to pollen production, dispersal, and fossilisation; sediment sampling; and nomenclature and taxonomy of the fossil pollen grains reflecting the vegetation that produced them. If the composition pattern of the most recent fossil pollen assemblage concords with those in modern or surface pollen assemblages from the same location(s), the pattern can be regarded as robust.Using recent (50–500 years) fossil pollen and surface pollen assemblages of angiosperms compiled from the same geographic area of Central Asia, we analyse spatial patterns in compositional turnover and phylogenetic dispersion. These are widely used to quantify different aspects of plant diversity.Despite differences in the data regarding spatial coverage, number of pollen records, and number of pollen taxa, the spatial pattern in the modern and fossil pollen-assemblage properties across climate zones is broadly similar. Especially, the latitudinal patterns of pollen-assemblage properties are strikingly similar between both data types. However, the degree of concordance varies according to the diversity metric being analysed, and the magnitudes of the metric may differ between both data types. When the data are compiled, processed, and standardised following consistent criteria and analysed using appropriate metrics and methods, spatial patterns in pollen-assemblage properties of fossil pollen data are as robust as those in surface pollen data (∼modern vegetation). Therefore, regional patterns of compositional turnover and phylogenetic dispersion can be confidently inferred from older fossil assemblages through the Holocene.

Functional analysis of the CaPIPLC5 gene in the regulation of the fertility restoration in pepper.

Cytoplasmic male sterility (CMS) is a very important factor to produce hybrid seeds, and the restoration of fertility involves the expression of many fertility-related genes. Our previous study showed that the expression of CaPIPLC5 was significantly up-regulated in pepper restorer accessions and minimally expressed in sterile accessions, speculating that CaPIPLC5 is related to the restoration of fertility. In this study, we further validated the function of CaPIPLC5 in the restoration of fertility. The results showed that CaPIPLC5 was specifically expressed in the anthers of the restorer accessions with the subcellular localization in the cytoplasm. Furthermore, the expression of CaPIPLC5 was significantly higher in restorer lines and restorer combinations than that in CMS lines and their maintainer lines. Silencing CaPIPLC5 led to the number of pollen decreased, pollen grains wrinkled, and the ratio of pollen germination reduced. In addition, the joint analysis of Yeast One-Hybrid (Y1H) and Dual-Luciferase (dual-LUC) assays suggested that transcription factors such as CaARF5, CabZIP24 and CaMYB-like1, interacted with the promoter regions of CaPIPLC5, which regulated the expression of CaPIPLC5. The present results provide new insights into the study of CaPIPLC5 involved in the restoration of fertility in pepper.

Acyl-CoA synthetase 1 plays an important role on pollen development and male fertility in tomato

The development of pollen is critical to male reproduction in flowering plants. Acyl-CoA synthetase (ACOS) genes play conserved functions in regulating pollen development in various plants. Our previous work found that knockout of the SlACOS1 gene in tomato might decrease fruit setting. The current study further revealed that SlACOS1 was important to pollen development and male fertility. The SlACOS1 gene was preferentially expressed in the stamen of the flower with the highest expression at the tetrad stage of anther development. Mutation of the SlACOS1 gene by the CRISPR/Cas9-editing system reduced pollen number and viability as well as fruit setting. The tapetum layer exhibited premature degradation and the pollen showed abnormal development appearing irregular, shriveled, or anucleate in Slacos1 mutants at the tetrad stage. The fatty acid metabolism in anthers was significantly impacted by mutation of the SlACOS1 gene. Furthermore, targeted fatty acids profiling using GC-MS found that contents of most fatty acids except C18:1 and C18:2 were reduced. Yeast complementation assay demonstrated that the substrate preferences of SlACOS1 were C16:0 and C18:0 fatty acids. Male fertility of Slacos1 mutant could be slightly restored by applying exogenous palmitic acid, a type of C16:0 fatty acid. Taken together, SlACOS1 played important roles on pollen development and male fertility by regulating the fatty acid metabolism and the development of tapetum and tetrad. Our findings will facilitate unraveling the mechanism of pollen development and male fertility in tomato.

Flowering phenology differs among wet and dry sub-alpine meadows in southwestern China.

The effect of floral traits, floral rewards and plant water availability on plant-pollinator interactions are well-documented; however, empirical evidence of their impact on flowering phenology in high-elevation meadows remains scarce. In this study, we assessed three levels of flowering phenology, i.e. population-, individual- and flower-level (floral longevity), in two nearby but contrasting (wet versus dry) sub-alpine meadows on Yulong Snow Mountain, southwestern China. We also measured a series of floral traits (pollen number, ovule number, and the ratio of pollen to ovule number per flower, i.e. pollen:ovule ratio [P/O]) and floral rewards (nectar availability and pollen presentation) as plausible additional sources of variation for each phenological level. Floral longevity in the wet meadow was significantly longer than that for the dry meadow, whereas population- and individual-flowering duration were significantly shorter. Our results showed a significant positive relationship between flowering phenology with pollen number and P/O per flower; there was no relationship with ovule number per flower. Further, we found a significant effect of flowering phenology on nectar availability and pollen presentation. Our findings suggest that shorter floral longevity in dry habitats compared to wet might be due to water-dependent maintenance costs of flowers, where the population- and individual-level flowering phenology may be less affected by habitats. Our study shows how different levels of flowering phenology underscore the plausible effects of contrasting habitats on reproductive success.

Variations of pollen concentration in urban alleys of park city and the transmission pattern during the period of high allergenic risk: Taking Qingyang District of Chengdu City as an example.

Pollen (spores and pollen) allergy caused by green areas is one of the most serious environmental epidemics endangering urban public health. The pollen allergy rate in China reached 17.8% in 2022, characterized by a wide age range of onset, severity and diversity of symptoms. The aims of this study were to verify the consistency of the prediction results of pollen concentration and the index of allergenicity of urban green zones (IUGZA) equation, and to clarify the dispersal pattern of tree pollen in the urban alleys of cities with high density of static wind. We selected representative high, medium and low allergenic areas based on the allergenic stress in urban alleys of Qingyang District, Chengdu calculated by IUGZA equation, and monitored the pollen concentrations by selecting points and indicator species within the three allergenic areas. There was a consistency in the variation of pollen concentration in urban alleys of the three areas, with the highest pollen concentration in March. Mean pollen concentration showed a pattern of spring > autumn > summer > winter. The main pollen sources belonged to Ginkgo, Platanus, Firmiana and Cedrus, accounting for 42.4%, 16.3%, 9.0% and 6.5% of the total pollen, respectively. Wind speed had the greatest effect on pollen concentration and its dispersal distance in the urban alley. The horizontal dispersal distance of pollen was up to 260 m, and the number of pollen showed a significant negative linear correlation with the distance away from the pollen sources. The concentration of exotic pollen collected at the high site (4.5 m above ground) was much lower than that at the near-ground site (1.5 m above ground), but without difference in the types of pollen. The results of allergenic risk predicted by the IUGZA equation were consistent with the actual measured pollen concentration, which could be used in high-density static wind city.

Contenu pollinique de l’atmosphère de la ville de Cotonou (Bénin) : cas des plantes ornementales

Aim of the studyThe present study consists in analyzing the pollen content of the atmosphere at three sites (Akpakpa, Cadjèhoun, and Vêdoko) of the city of Cotonou (Benin) to know the quantitative and qualitative composition of pollens. MethodPollens were trapped on a microscopic slide coated with silicone oil under the SLT sensor. The direct field observation method was used to identify flowering species from November 2019 to November 2020. ResultsIn total 19,921 pollen grains were counted. Ornamental plants pollens represent 28.23% against 71.76% for non-ornamental plants, and dominant in the air during rainy seasons. More than 50% of the species were always in flower, but the months from August to November 2020 are richer in flowering. The pollen spectrum showed that: Pithecellobium dulce, Acacia auriculiformis, Terminalia mantaly, Euphorbia milii, Celosia cristata, Acalypha wilkesiana, and Casuarina equisetifolia are the most common ornamental species in the atmosphere of Cotonou. ConclusionThe rainy and short dry seasons are the peak flowering periods for ornamental species in Cotonou City. Their pollen abundance in the atmosphere is low compared with non-ornamental species. As for temperature, it has a significant influence on pollen dispersal: when it rises, so does the number of pollens in the air.

Community-wide patterns in pollen and ovule production, their ratio (P/O), and other floral traits along an elevation gradient in southwestern China

BackgroundAs the male and female gametophytes of flowering plants, pollen and ovules largely determine the upper and lower boundaries of plant reproductive success. It is commonly predicted that pollen and ovule number per flower should increase, and pollen-ovule ratio (P/O) per flower should decrease with increasing elevation in response to a more stochastic pollination environment. Here, we aimed to determine the response of pollen number, ovule number, and P/O to other floral traits and elevation gradients for 84 insect-pollinated herbaceous flowering plant species in five sub-alpine and alpine communities (2709 to 3896 m a.s.l.) on Yulong Snow Mountain, southwestern China.ResultsSix floral traits, including P/O, floral display area, flower number, tube depth, flower shape, and pollen presentation, were highly correlated with pollen and ovule number per flower. With increasing elevation, pollen number and P/O per flower increased marginally and significantly, respectively; ovule number per individual, flower number per individual, stigma stamen separation, and inflorescence height decreased significantly. However, ovule number per flower and other floral traits (i.e., floral display area, tube depth, stigma height, stamen height, and pollen and P/O per individual) did not change with elevation. We detected significant phylogenetic signals for pollen number, ovule number, and P/O, suggesting that these traits may be highly conserved and with limited response to changing environmental conditions.ConclusionsResults revealed patterns of plant reproductive character evolution along elevation gradients and the potential factors governing their spatial variation in high-elevation environments. Plant species at high elevations are more likely adapted to cross-pollination, indicated by increased P/O per flower at high elevations on Yulong Mountain. Combined effects of phylogenetic history and plant-pollinator interactions should determine plant trait evolution.

Genomic mechanisms and consequences of diverse postzygotic barriers between monkeyflower species.

The evolution of genomic incompatibilities causing postzygotic barriers to hybridization is a key step in species divergence. Incompatibilities take two general forms - structural divergence between chromosomes leading to severe hybrid sterility in F1 hybrids and epistatic interactions between genes causing reduced fitness of hybrid gametes or zygotes (Dobzhansky-Muller incompatibilities). Despite substantial recent progress in understanding the molecular mechanisms and evolutionary origins of both types of incompatibility, how each behaves across multiple generations of hybridization remains relatively unexplored. Here, we use genetic mapping in F2 and RIL hybrid populations between the phenotypically divergent but naturally hybridizing monkeyflowers Mimulus cardinalis and M. parishii to characterize the genetic basis of hybrid incompatibility and examine its changing effects over multiple generations of experimental hybridization. In F2s, we found severe hybrid pollen inviability (< 50% reduction vs. parental genotypes) and pseudolinkage caused by a reciprocal translocation between Chromosomes 6 and 7 in the parental species. RILs retained excess heterozygosity around the translocation breakpoints, which caused substantial pollen inviability when interstitial crossovers had not created compatible heterokaryotypic configurations. Strong transmission ratio distortion and inter-chromosomal linkage disequilibrium in both F2s and RILs identified a novel two-locus genic incompatibility causing sex-independent gametophytic (haploid) lethality. The latter interaction eliminated three of the expected nine F2 genotypic classes via F1 gamete loss without detectable effects on the pollen number or viability of F2 double heterozygotes. Along with the mapping of numerous milder incompatibilities, these key findings illuminate the complex genetics of plant hybrid breakdown and are an important step toward understanding the genomic consequences of natural hybridization in this model system.

Summer grazing change fitness in a Tibetan lotus

It is believed that grazing has an effect on the functioning and performance of flowers, as well as their association with pollinator preferences and plant reproduction. However, the effects of grazing time on nectar secretion and pollen removal are still not fully understood. We hypothesized that seasonal grazing influences pollinator visitation and pollen removal by altering above-ground biomass and nectar secretion. In this study, we conducted field experiments to measure above-ground biomass, flower number per capitulum and capitulum number per plant, nectar volume and concentration, pollinator visitation of male- and female-phase flowers, pollen removal (e.g., number of pollens exported and deposition on a pollinator body and stigma), seed set ratio, and seed number between summer and winter grazing pastures of Saussurea stella. Our findings demonstrated that summer grazing reduced the above-ground biomass, nectar secretion, and pollinator visitation of male-phase flowers, thereby decreasing pollen export. There was a positive correlation between nectar secretion and above-ground biomass, as well as between pollinator visitation and nectar secretion, the number of pollens exported, and pollinator visitation of male-phase flowers. Experiments involving the removal of leaves revealed that a decrease in above-ground biomass was associated with a decrease in nectar secretion, pollinator visitation of male-phase flowers, and pollen removal. However, plants growing in summer and winter grazing pastures had comparable nectar secretion, pollinator visitation of female-phase flowers, seed number, and seed set ratio. Our results suggested that seasonal grazing influences nectar rewards, pollinator preferences, pollen removal, and male fitness. These findings would shed new light on the influence of herbivores on plant-pollinator interactions in the Tibetan meadow.

Stingless bee (Tetragonula carbonaria) foragers prioritise resin and reduce pollen foraging after hive splitting

Stingless bees are increasingly in demand as pollinators in agricultural crops within the tropics and subtropics. Hive splitting, where one strong managed hive is “split” into two independent daughter colonies, is commonly used to increase hive numbers. However, how splitting impacts foraging behaviour or the time taken for the colony to recover from splitting has not previously been studied. We assessed the impact of splitting on the foraging behaviour of Tetragonula carbonaria colonies. The number of returning forager trips and foraged proportions of pollen, nectar and resin was observed after splitting and compared with unsplit control hives over a 31-day period. We found the total amount of returning foragers in split hives reduced to less than a third of unsplit hives (unsplit median, 184–288; split median, 19–61) for 16 days, while returning nectar (unsplit median, 89–147; split median, 16–28) and pollen (unsplit median, 55–155; split median, 1–7) foragers reduced to less than a quarter of unsplit hives for 9 days following splitting. After 31 days, the number of total, nectar and pollen foraging trips had still not recovered to levels observed in unsplit hives. Resin foraging trips however were not significantly different to unsplit hives after only 10 days. The colony foraging allocation to resin (proportion) increased after splitting and was significantly higher in split hives until day 16 of the experiment (unsplit median, 0.03–0.05; split median, 0.10–0.16). Our results demonstrate that split colonies prioritise resin collection and foraging on floral resources is reduced. We recommend that hives should not be split within 31 days of being used for pollination, and resin sources should be conserved where possible and supplemented where necessary due the vital roles of the resource.

EFFECTS OF DROUGHT STRESS ON GROWTH AND YIELD PARAMETERS OF ZEA MAYS- A COMPREHENSIVE REVIEW

Maize serves as an important food source for human and livestock populations and its demand is heightening in response to the ever-increasing global population. Maize uses a total of 350-450 mm of water during its lifetime to complete its growth and development. However, as a result of global climate change and increased human activity, a significant portion of the Earth’s land is suffering from drought, leading to frequent periods of dryness that hamper the production of maize. This review article recounts the consequences of imposing moisture stress on various developmental stages, phenology, morphology, harvest, and yield-attributing characteristics of the maize crop. To form this review article, research papers expatiating on the consequences faced by maize crops in response to moisture stress were retrieved to gain a thorough understanding of the subject. Drought stress affected both vegetative and reproductive growth stages of the maize plant with significant alterations in seed germination, biomass accumulation, days to anthesis and silking, pollen number, kernel number, kernel weight, grain yield, nutrient uptake, and soluble proteins. The result has shown a decline in the yield of maize by 70% in response to moisture stress imposed by drought conditions. The development of drought-resistant lines and irrigation facilities is thus expected to salvage crops and farmers from an impending crisis of drought spells brought about by climate change.

ZmRPN1 confers quantitative variation in pollen number and boosts hybrid seed production in maize.

The number of pollen grains is a critical determinant of reproductive success in seed plants and varies among species and individuals. However, in contrast with many mutant-screening studies relevant to anther and pollen development, the natural genetic basis for variations in pollen number remains largely unexplored. To address this issue, we carried out a genome-wide association study in maize, ultimately revealing that a large presence/absence variation in the promoter region of ZmRPN1 alters its expression level and thereby contributes to pollen number variation. Molecular analyses showed that ZmRPN1 interacts with ZmMSP1, which is known as a germline cell number regulator, and facilitates ZmMSP1 localization to the plasma membrane. Importantly, ZmRPN1 dysfunction resulted in a substantial increase in pollen number, consequently boosting seed production by increasing female-male planting ratio. Together, our findings uncover a key gene controlling pollen number, and therefore, modulation of ZmRPN1 expression could be efficiently used to develop elite pollinators for modern hybrid maize breeding.

Multi-omics research on common allergens during the ripening of pollen and poplar flocs of Populus deltoides.

Populus deltoides is widely cultivated in China and produces a large number of pollen and poplar flocs from March to June per year. Previous studies have found that the pollen of P. deltoides contains allergens. However, studies on the ripening mechanism of pollen/poplar flocs and their common allergens are very limited. Proteomics and metabolomics were used to study the changes of proteins and metabolites in pollen and poplar flocs of P. deltoides at different developmental stages. Allergenonline database was used to identify common allergens in pollen and poplar flocs at different developmental stages. Western blot (WB) was used to detect the biological activity of common allergens between mature pollen and poplar flocs. In total, 1400 differently expressed proteins (DEPs) and 459 different metabolites (DMs) were identified from pollen and poplar flocs at different developmental stages. KEGG enrichment analysis showed that DEPs in pollen and poplar flocs were significantly enriched in ribosome and oxidative phosphorylation signaling pathways. The DMs in pollen are mainly involved in aminoacyl-tRNA biosynthesis and arginine biosynthesis, while the DMs in poplar flocs are mainly involved in glyoxylate and dicarboxylate metabolism. Additionally, 72 common allergens were identified in pollen and poplar flocs at different developmental stages. WB showed that there were distinct binding bands between 70 and 17KD at the two groups of allergens. A multitude of proteins and metabolites are closely related to the ripening of pollen and poplar flocs of Populus deltoides, and they contain common allergens between mature pollen and poplar flocs.

Allelic haplotype combinations at the MS-P1 region, including P-class pentatricopeptide repeat family genes, influence wide phenotypic variation in pollen grain number through a cytoplasmic male sterility model in citrus.

In citrus breeding programs, male sterility is an important trait for developing seedless varieties. Sterility associated with the male sterile cytoplasm of Kishu mandarin (Kishu-cytoplasm) has been proposed to fit the cytoplasmic male sterility (CMS) model. However, it remains undetermined whether CMS in citrus is controlled by interactions between sterile cytoplasm and nuclear restorer-of-fertility (Rf) genes. Accordingly, mechanisms underlying the control of the wide phenotypic variation in pollen number for breeding germplasm should be elucidated. This study aimed to identify complete linkage DNA markers responsible for male sterility at the MS-P1 region based on fine mapping. Two P-class pentatricopeptide repeat (PPR) family genes were identified as candidates for Rf based on predicted mitochondrial localization and higher expression in a male fertile variety/selected strain than in a male sterile variety. Eleven haplotypes (HT1-HT11) at the MS-P1 region were defined based on genotyping of DNA markers. Association analysis of diplotypes at the MS-P1 region and the number of pollen grains per anther (NPG) in breeding germplasms harboring Kishu-cytoplasm revealed that the diplotypes in this region influenced NPG. Among these haplotypes, HT1 is a non-functional restorer-of-fertility (rf) haplotype; HT2, a less-functional Rf; HT3-HT5 are semi-functional Rfs; and HT6 and HT7 are functional Rfs. However, the rare haplotypes HT8-HT11 could not be characterized. Therefore, P-class PPR family genes in the MS-P1 region may constitute the nuclear Rf genes within the CMS model, and a combination of the seven haplotypes could contribute to phenotypic variation in the NPG of breeding germplasms. These findings reveal the genomic mechanisms of CMS in citrus and will contribute to seedless citrus breeding programs by selecting candidate seedless seedlings using the DNA markers at the MS-P1 region.

Beyond pollen:ovule ratios: Evolutionary consequences of pollinator dependence and pollination efficiency for pollen and ovule production in angiosperms.

The relative per-flower production of ovules and pollen varies broadly with angiosperm mating systems, with outcrossing types commonly producing more pollen grains per ovule than selfing types. The evolutionary causes of this variation are contentious, especially the relevance of pollination risk. Resolution of this debate may have been hampered by its focus on pollen:ovule (P:O) ratios rather than on the evolution of pollen and ovule numbers per se. Using published mean ovule and pollen counts, we analyzed associations with the proportion of removed pollen that reaches stigmas (pollen-transfer efficiency) and differences between pollinator-dependent and autogamous forms within and among species. Analyses involved Bayesian methods that simultaneously considered variation in pollen and ovule numbers and accounted for phylogenetic relatedness. We also assessed the utility of P:O ratios as mating-system proxies and their association with female outcrossing rates. Median pollen number declined consistently with pollen-transfer efficiency among species, whereas median ovule number did not. Similarly, in both intraspecific and interspecific analyses, pollinator-dependent plants produced more pollen than autogamous plants, whereas ovule production did not differ statistically. Distributions of P:O ratios overlapped extensively for self-incompatible and self-compatible species and for different mating-system classes, and P:O ratios correlated weakly with outcrossing rate. Our findings demonstrate that pollinator dependence and pollination efficiency commonly influence the evolution of pollen number per flower but have more limited effects on ovule number. P:O ratios provide ambiguous, possibly misleading, information about mating systems, especially when compared among clades.

The Neogene-Quaternary palynological record of Castanea in the American southeast

The genus Castanea, divided into seven extant species of trees worldwide, includes the American chestnut, C. dentata. This once common North American tree has been nearly eliminated from the landscape due to the appearance of chestnut blight early in the Twentieth Century. Castanea has a long history as a component of palynological assemblages, though megafossil paleobotanical remains are quite rare. The distributions of what are believed to be Castanea pollen as they have been derived from coastal plain and near-shore sediments dating back to the Neogene of the coastal plain of the southeastern US are discussed. The abundances of Castanea pollen in microfossil preparations are carefully considered relative to the concept of ‘pollen sum’ and while it appears that the trees were quite abundant as components of coastal woodlands during the Neogene, the actual number of pollen we found in samples is quite low. American chestnut trees continued to be important into the late Pleistocene and through the time when humans first occupied both coastal and inland areas of the southeastern US.

Characterisation of Kastamonu honeys by palynological and physicochemical methods

Thirty-three honey samples were collected between 2017 and 2018 in Kastamonu Province, in order to characterise the palynological and physico-chemical properties of the honey produced in the western Black Sea region of Türkiye. Melissopalynological characteristics of the honey samples were determined based on the total pollen number in 10 g (TPN-10 g) along with the pollen taxa diversity. The physicochemical properties of the samples including humidity ratio, volatile organic compounds, total phenolic content, fructose/glucose ratio and hydroxymethylfurfural (HMF) content were determined using a refractometer, gas chromatography coupled with mass spectrometry (GC–MS), ultraviolet-visible spectrometry and high-performance liquid chromatography, respectively. Melissopalynological analysis revealed that the honey samples contain 49 taxa, of which 18 were determined at family level and 31 were determined at genus level. The most common taxon was Castanea sativa while the other important taxa were Apiaceae, Asteraceae, Amaranthaceae, Boraginaceae, Brassicaceae, Fabaceae and Lamiaceae. Eleven out of 33 honey samples were monofloral and the remaining 22 samples were multifloral. According to the TPN-10 g results of the honey samples, the total number of pollens in 10 g of Kastamonu honey was between 1051 and 325 108 pollen grains. The moisture ratio was obtained between 11.9 and 18.9% while the fructose + glucose values were between 35.84 and 84.1 g/100 g. HMF content varied between 0.38 and 21.31 ppm while the total phenolic content varied between 39.6 and 138.8 mg GAE/100 g. The GC–MS analysis revealed that the samples contain compounds belonging to the groups of aldehydes, aliphatic acid and its esters, alcohols, hydrocarbons, flavonoids, carboxylic acid and esters, ketones, and sugars.

Testing the Effect of Relative Pollen Productivity on the REVEALS Model: A Validated Reconstruction of Europe-Wide Holocene Vegetation

Reliable quantitative vegetation reconstructions for Europe during the Holocene are crucial to improving our understanding of landscape dynamics, making it possible to assess the past effects of environmental variables and land-use change on ecosystems and biodiversity, and mitigating their effects in the future. We present here the most spatially extensive and temporally continuous pollen-based reconstructions of plant cover in Europe (at a spatial resolution of 1° × 1°) over the Holocene (last 11.7 ka BP) using the ‘Regional Estimates of VEgetation Abundance from Large Sites’ (REVEALS) model. This study has three main aims. First, to present the most accurate and reliable generation of REVEALS reconstructions across Europe so far. This has been achieved by including a larger number of pollen records compared to former analyses, in particular from the Mediterranean area. Second, to discuss methodological issues in the quantification of past land cover by using alternative datasets of relative pollen productivities (RPPs), one of the key input parameters of REVEALS, to test model sensitivity. Finally, to validate our reconstructions with the global forest change dataset. The results suggest that the RPPs.st1 (31 taxa) dataset is best suited to producing regional vegetation cover estimates for Europe. These reconstructions offer a long-term perspective providing unique possibilities to explore spatial-temporal changes in past land cover and biodiversity.