Pollen Research Articles

Modern pollen distribution along a Himalayan elevation gradient in Central Nepal

Modern pollen distribution and its relationship to environmental variables in tropical to alpine vegetation zones are investigated to provide a reference for palaeoenvironmental reconstructions and to improve the understanding of pollen dispersal patterns in Central Nepal. A total of 100 samples (from soil and moss) were collected from along an elevational gradient ranging from 173 to 4615 m above sea level. Results show that the alpine zone is dominated by arboreal pollen (AP) and the sub-alpine zone also shows good representation of coniferous taxa pollen such as Pinus, Abies, Tsuga, and Picea along with Ericaceae. The temperate zone has a good representation of Quercus (Evergreen) and Pinus pollen, whereas the sub-tropical zone is characterized by Alnus pollen and agricultural taxa such as Cerealia (planted Poaceae) and Brassicaceae. In the tropical zone, non-arboreal pollen (NAP), mainly Cerealia dominate, reflecting intensive agricultural practices. Shorea is completely silent in pollen representation. A redundancy analysis indicates that elevation is the primary factor influencing pollen distribution in this region. Overall, the pollen data reflect the vegetation distribution but Pinus is over-represented and Shorea is unrepresented, which should be taken into consideration when interpreting fossil pollen in Central Nepal.

Taxonomic insights into medicinal plants pollen, using advanced microscopy techniques, from the Western Ghats, India

Pollen morphological study on 18 medicinal plants from the Western Ghats (India) was carried out using light microscopy (LM), confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) techniques. The principal aim was to obtain high-resolution three-dimensional images and ultra-structure of the pollen grains of the studied taxa. The palyno-morphological characters, such as polar axis, equatorial diameter, P/E ratio, pollen shape, aperture type and number, exine thickness and surface ornamentation will be useful in the identification and taxonomic classification of the studied medicinal plants. Statistical analysis reveals grouping of the taxa in three different clusters and also isolated presence of taxa on the principal component analysis (PCA) biplot, irrespective of their families, showing similarities and/or variations among the studied taxa, belonging to the same and/or different families. The present study has taxonomic significance, providing high taxonomic resolution (identification of the taxa up to species level), and further aid in the identification and delimitation of the 18 studied plants.

Ultrastructural study of pollen and tapetum development in Hydrocleys nymphoides, Alisma plantago-aquatica, and Sagittaria montevidensis (Alismataceae).

The Alismataceae family, widely distributed across tropical temperate swamps and wetlands, includes 15 genera post-merger with Limnocharitaceae. In Argentina, six genera are represented across three clades. Embryological characters, notably the male gametophyte and anther, are crucial in taxonomy due to their stability against environmental changes. This study aims to analyze the ultrastructure of the tapetum and pollen grain development in three economically and ecologically important species representing each clade: Sagittaria montevidensis (Clade A), Hydrocleys nymphoides (Clade B), and Alisma plantago-aquatica (Clade C). Anthers at different developmental stages were processed according to classic techniques for their observation with bright-field and transmission electron microscopy. The three studied species within the Alismataceae family exhibit similar reproductive characteristics. Seven stages of pollen grain development were identified. The microsporogenesis is successive with a regular meiosis. The ultrastructure of the tapetal cells shows similarities to other species with plasmodial tapetum. During the microspore tetrad stage, there is tapetal hyperactivity and an increase in secretion processes. In the free microspore stage, the tapetal cells lose their walls and increase the amount of rough endoplasmic reticulum forming a network of cisternae that extend into evaginations. Later cells completely invade the anther locule and fuse to form a tapetal plasmodium. No peritapetal membrane with orbicules was observed. Pollen is released at the tricellular stage. The pollen grain wall presents an ectexine with a basal layer, columellae, and tectum with supratectal spines while an endexine is not observed in any of the three species. This research enhances the understanding of tapetal cell interactions with developing pollen grains and contributes to the knowledge of the ultrastructure of plasmodial tapetum. Moreover, these findings highlight evolutionary reproductive patterns in Alismataceae, suggesting the plasmodial tapetum as a synapomorphy for the order.

A leucine-rich-repeat receptor-like kinase regulates pollen aperture formation in rice.

Apertures in pollen grains exhibit species-specific patterns and provide an ideal model for studying cell-surface patterning. Pollen apertures are critical for cereal crop fertility, and while DEFECTIVE IN APERTURE FORMATION1 (OsDAF1) and INAPERTURATE POLLEN1 (OsINP1) have been documented to participate in pollen aperture formation in rice (Oryza sativa), the molecular transduction pathway regulating aperture formation is largely unknown. Here, we report that a leucine-rich-repeat receptor-like kinase (LRR-RLK), AM1, plays a key role in rice pollen aperture formation. Mutations of OsAM1 lead to complete sterility due to disappearance of the pollen aperture and failure in pollen tube germination. OsAM1 encodes a LRR-RLK that belongs to the STRUBBELIG-receptor family. Similar to other reported aperture regulators, OsAM1 assembles to future aperture sites on tetrads after meiosis to regulate aperture formation. The extracellular and intracellular domain of OsAM1 interacts with OsINP1 and OsDAF1, respectively. However, despite their interaction and the absence of aperture formation in osam1 pollen grains, OsINP1 and OsDAF1 localize to future aperture sites at the tetrad stage. Mutation of OsINP1, however, disrupts normal localization of OsAM1, indicating that OsAM1 acts downstream of OsINP1. Our findings reveal the role of a LRR-RLK protein in pollen aperture formation and shed light on the regulatory network of pollen aperture formation.

Skin Prick Tests and Enzyme-Linked Immunosorbent Assays among Allergic Patients Using Allergenic Local Pollen Extracts.

Allergic respiratory diseases are prevalent in the Philippines, with allergic rhinitis and asthma occurring at 20% and 8.7% of the population, respectively. The diagnosis of respiratory allergies is achieved by a combination of patient history and different screening tools, especially for the identification of the allergic triggers such as allergy skin prick test (SPT) and serum-specific IgE enzyme-linked immunosorbent assays (sIgE ELISA). The Philippines, being a tropical country, have a wide variety of plant species with potential to produce allergenic pollen grains. Knowledge of the sensitization profiles of Filipino allergic patients to our local pollen allergens is currently limited. The aim of this study is to determine the sensitization profile of patients with respiratory allergies (allergic rhinitis and/or asthma) through the allergy skin prick test (SPT) using allergenic local pollen extracts. It also aimed to determine if there is a positive agreement between the SPT and sIgE ELISA positivity rate and whether the results have relationship with the pollen purity and the protein content of the extracts. Pollen allergens were extracted from Amaranthus spinosus (pigweed), Mimosa pudica (makahiya), Tridax procumbens (wild daisy), Imperata cylindrica (cogon), Oryza sativa (rice), Pennisetum polystachion (foxtail grass), Sorghum halepense (Johnson grass), Albizia saman (acacia), Cocos nucifera (coconut), Leucaena leucocephala (ipil-ipil), and Mangifera indica (mango). SPT was performed at the Allergy Clinic of the University of the Philippines-Philippine General Hospital on patients with allergic rhinitis and/or bronchial asthma. Blood samples were collected from patients who developed wheal diameters of 3 mm or more than the negative control. Sera were tested against the same pollen extracts using ELISA. Of the one hundred sixty-five (165) patients who submitted for skin prick test, 129 showed positive SPT results to the pollen extracts. Weeds were the most sensitizing (51.9%-58.1%). Blood samples were collected from these patients and tested for sIgE ELISA and among them, 71 were positive in the sIgE ELISA. Highest sensitization rates in sIgE ELISA were found in coconut, pigweed, Johnson grass, and rice. The highest positive agreements or the proportion of patients with positive sIgE ELISA among those with positive SPT were in coconut, followed by Johnson grass, pigweed, and rice. Most of the pollen sensitized patients on SPT are polysensitized. SPT is a safe, simple, and rapid method for the diagnosis of IgE-mediated allergy. The lower number of positive patients in sIgE ELISA may be attributed to the low serum IgE levels and low quantities of effectual allergen components in extracts. Results of both SPT and ELISA must be correlated with a patient's clinical history, particularly the patient's exposures, and physical examination.

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.

Pollen morphology reveals genetic diversity between some superior sour cherry (Prunus cerasus L.) genotypes; an opportunity for expanding breeding possibilities

AbstractPreservation of the genetic diversity of sour cherry in Iran is imperative for the development of improved cultivars tailored to specific ecological conditions. Addressing gaps in research concerning ecological adaptation, resource management and international collaboration related to sour cherry genetic resources in Iran is essential. Bridging these research lacunae can facilitate the implementation of sustainable cultivation practices, optimize production systems and enhance the global utilization of sour cherry genetic diversity. A comprehensive analysis of the morphology and ultrastructure of pollen grains from ten native sour cherry genotypes in Iran was conducted over a two-year period using scanning electron microscopy (SEM). The examination revealed that all pollen grains were unipolar, radially symmetrical and tricolpate. The length and width of pollen grains varied among genotypes, with lengths ranging from 42.17 to 57.57 μm and widths from 20.28 to 28.13 μm. Furthermore, all genotypes exhibited prolate pollen grains, with differing colpus lengths. Examination of pollen exine revealed striate shapes with varying numbers of ridges, ranging from 18.5 to 8.5 furrows per 50 m2. The horizontal area of pollen grains varied from 333.28 to 1491.69 μm. Polar perspective analysis showed considerable variation in the distance between mesocolpium endpoints. Sour cherry displays significant genetic diversity in Iran, and the application of SEM has proven instrumental in characterizing this diversity. This understanding will aid in further breeding research aimed at enhancing sour cherry varieties and their adaptation to specific ecological conditions.

Pollination ecology in Centrosema brasilianum (L.) Benth. (Fabaceae: Papilionoideae): bee size influences pollen deposition

Here, were observed the interaction between Centrosema brasilianum (Fabaceae, Papilionoideae) and their floral visitors and quantified pollen removal and visitor traits. Aims: for to determine whether the behavior, quantity, and location of deposited pollen on the body of visiting bees differs according to the body size of bees. Methods: the morphological and behavioral attributes of floral and bees observed in interaction were measured in 20 individuals of C. brasilianum. The place of deposit and the amount of polinic charge in each bee were identified. The relationship between the attributes of the interactants and of pollen deposited was determined using simple linear models. Results: Bee behavior and pollen deposition on the body varied according to bee body size. Larger-sized bees with long tongues raised floral keels during visits and pollen deposition occurred on their heads and dorsal surfaces. Smaller individuals with short tongues did not raise the keel, and pollen was deposited on the dorsal surface, but mostly over the wings. Additionally, larger bees had twice as many pollen grains deposited on their body surfaces than smaller bees. Conclusions: we assumed that larger bees may provide a more effective pollination service than smaller bees in C. brasilianum. Implications: Future evaluations should be conducted that include more morphological and behavioral attributes in a larger sample number, which would provide a more nuanced understanding of pollination efficiency, the relationship between different behaviors and body sizes of bees, and the consequences of differential pollen deposition on the reproductive success of C. brasilianum.

The effects of long-term radiation exposure on the reproductive structures of Glyceria maxima (Hartm.) Holmb.: A case study in the Chornobyl exclusion zone

During the acute phase of the Chornobyl accident the biota of the contaminated area was exposed to high doses of ionising radiation. Although these doses decreased significantly over the years, the exposure persisted over a prolonged period. This long-term exposure can be considered as a direct cause of genetic modifications occurring in organisms, and the search for correlative changes in the state of biota under the impact of radioactive contamination is an extremely urgent task. The aquatic macrophyte Glyceria maxima is the most common coenosis-forming plant of the littoral vegetation of the floodplain water bodies in the Chornobyl Exclusion Zone, and is capable of concentrating radionuclides in significant quantities. In this study, we aim to determine whether long-term radiation exposure has affected organs of reproductive structure (flower, pollen, seed) and, consequently, the viability of local populations of this species. All the traits analysed showed an inverse relationship with the absorbed dose rate of the maternal plants. It was determined that with an increase in the absorbed dose rate, the pollen size decreases, and the range of individual grains in the sample begins to vary more: small, heterogeneous in shape and size pollen grains are formed. Additionally, a decrease in pollen grain size correlates with a decrease in the proportion of fertile pollen. Pollen grains viability (fertility) decreases by 20–40% with increasing radiation dose rate. The response of reproductive structures to radiation exposure is non-linear: already at low doses (>2 μGy/h), negative changes in functional and morphological traits are observed, while at higher doses (9–13 μGy/h), the changes slow down. It is assumed that the radiation exposure mainly affects the early reproductive stages (pollen grains and partially flowers), while the main nutrients in water, that determine the trophic status of the reservoir, affects the late stages (seeds).

SOLITARY BEES (HYMENOPTERA: APOIDEA) DIVERSITY AND PALYNOLOGICAL ANALYSIS OF THEIR ASSOCIATED FLORAL RESOURCES IN WESTERN EGYPT

Egypt is one of the important countries in bee diversity of Northern Africa. The Eastern part of the country was studied in several works in the last decade comparing to the western part. Here we address the diversity of solitary bees in Alexandria Governorate at Al Hawaria region 30 57’13” N 29 40’27” E during two years of works in 2021 and 2022. The total species number found in the region was 50 species (25 of Apidae, 16 of Megachilidae, 5 of Andrenidae 3 of Halictidae and one species of Colletidae). The identification of some pollen grains collected from plants and some solitary bee species revealed that reference slides of pollen grains from 32 flowering plant species (crops and wildflowers), belonging to 19 plant families was done in this work. The preference of plant families was varied between different bee genera. The most represented families visited by bees were Asteraceae, Brassicaceae and Fabaceae, they contributed by 58% of the total bee flora. The pollen spectrum in the study nest of Xylocopa aestuans was composed of a total of two pollen types, while the nest of Osmia sp was composed of one type of pollen.

A Detailed Sedimentological Analysis of Colour Lake, Axel Heiberg Island, Nunavut

This research project examines sediments in Colour Lake, a non-glacial lake on Axel Heiberg Island in the Canadian High Arctic. Analyzing the mineralogical composition, structural morphology and deposition patterns of the accumulated lake sediments provides information about the depositional environment and can serve as proxies for past environmental conditions. Work focused primarily on a 53 cm long sediment core collected in 2019. The objectives were: (1) to document distinct sediment units and interpret their depositional history by high resolution image analysis and microscopic observations in thin sections; (2) to identify schwertmannite, an iron oxyhydroxy-sulfate mineral within the sediments using scanning electron microscopy and x-ray fluorescence (XRF); (3) to determine this mineral’s relationship with siliciclastic deposits; and (4) to establish sediment chronology by 210Pb and 137Cs dating. Data was organized into pollen charts, incorporating images, scans, sediment stratigraphy, and grain size distributions to better understand sediment layers and their positions within the core. Thirteen lithozones were identified based on observed variations in the core, differing in terms of mud and clay lens distribution, the presence of schwertmannite, lamination patterns (graded or non-graded detrital laminations), the occurrence of biological components, and detrital mineral grain sizes. A recurring lithozone featuring non-graded, amorphous clay with schwertmannite, typically overlying either graded or reverse-graded mud, was observed throughout the core. While the mechanisms responsible for sediment deposition have not been fully explored, they are suspected to be related to hyperpycnal flows and slumping events. An Intervaled Sediment Extruder (ISE) was developed for precise sediment extrusion from a core collected in July for 210Pb and 137Cs dating, which will constrain sedimentation rates and correlate depositional events with past environmental conditions. Future work will focus on linking sediment structures to climatic events, identifying annually laminated layers (varves), and completing dating analyses to better understand past climate variations.

Aerobiology of Olive Pollen (Olea europaea L.) in the Atmosphere of the Iberian Peninsula

Olea europaea L. pollen is one of the main causes of pollinosis and respiratory diseases in the Iberian Peninsula (IP). The aim of this study was to provide a pollen calendar in different regions of the IP, which could help allergists and allergic patients in the management of Olea europaea allergic diseases, and to update/complement what has already been reported on olive trees’ aeropalynology in this region. Airborne Olea pollen dynamics were analyzed over a period of 8 years in a total of 21 localities, 7 in Portugal and 14 in Spain. Airborne pollen monitoring was carried out using the Hirst-type spore trap method and following the recommendations of the Quality Control Working Group of the European Aerobiology Society. The daily pollen count, the annual pollen profile, the Annual Pollen Integral (APIn), the Seasonal Pollen Integral (SPIn) and the Pollen Peak, all expressed in number of pollen grains per cubic metre of air, together with the main pollen season and its characteristics, the Start Day, the End Day and the length of the pollen season, were calculated for each sampling station. Differences in mean Olea pollen concentration between odd and even years were also analyzed. On average, the main pollen season (MPS) started in April/May and ended in June, with Pollen Peaks recorded in May, except in Burgos, where it was recorded in June. The longest MPS occurred in Lisbon, Oviedo and Valencia (53 days) and the shortest in Vitoria (25 days). A high daily pollen concentration (i.e., >200 grains/m3) was recorded between 1 and 38 days along the year in all sampling stations of the southwest quadrant of the IP and in Jaén. A biannual pattern, characterized by alternating years of high and low pollen production, was found in the southwest of the IP. In conclusion, the study provided a deeper understanding of the pollination behaviour of olive trees in the IP and allowed the establishment of a representative Olea pollen calendar for this region. In addition, our results suggest the usefulness of investigating more detailed relationships between annual Olea pollen, allergen sensitization and symptoms, both for allergists involved in the study and management of allergic respiratory diseases caused by this species and for the self-management of disease in allergic subjects.

Palynological characterization of succulents of the families Asphodelaceae and Asteraceae

This study aimed to analyze palynologically succulent species: Asphodelaceae: Haworthia chloracantha Haw., Haworthia cymbiformis (Haw.) Duval, Haworthia limifolia (=Haworthiopsis limifolia) Marloth and Asteraceae: Othonna capensis LH Bailey and Senecio peregrinus Griseb. Closed buds were preserved in acetic acid, the acetolyzed grains were arranged on microscope slides, and 50 pollen grains of each species were photographed. Using light optical microscopy, measurements were made of each grain in the polar and equatorial views, in micrometers (µm). For scanning electron microscopy (SEM), the anthers were macerated on microscope slides to release the grains, which were metallized with gold-palladium and photographed. In Asphodelaceae, the grains are monads, monosulcate, medium to large in size, elliptical in scope, bilaterally symmetric, heteropolar, with foveolate, ornamentation microreticulate, perforated, mean exine thickness 1.98-1.42-2.21 micrometers. In Asteraceae, the grains are monads, tricolporate, medium in size, circular to subcircular in scope, radially symmetric, isopolar, oblate-spheroidal and prolate-spheroidal in shape, with perforated echinate ornamentation, average exine thickness 4.08-4.41 micrometers. The pattern of the grains of Haworthia are in line with literature of Asphodelaceae, although the verrucate exine was not observed in this study. For Othonna and Senecio, the echinate ornamentation and thicker exine are in line with the pattern of the Asteraceae.

Stanley and Acetolysis: Enhanced Method for Pollen Identification and Geolocation of Cocaine Samples

The concept of palynological assemblage, a set of all identifiable pollen grains and spores, is very useful in geolocation determinations in Forensic Studies. To identify plant genera, palynologists must recognize detailed aspects of apertures, ornamentation and layers on the cell wall. Pollen and spores recovered from higher purity cocaine samples represent an alternative to indicate drug source regions. After following the method established by Stanley in 1992, we added the acetolysis procedure in samples seized by the Civil Police of the State of Sao Paulo, Brazil, in 2017, in order to enhance morphological traits observation and taxonomical identification of different pollen taxa, allowing reliable environmental and geolocation reconstructions.

Computerized Principal Component–Canonical Discriminant Analysis Classification Model for Pollen Grain Identification Using Surface-Enhanced Raman Spectroscopy

Pollen identification and quantification are employed in various applications, and studies have been conducted to achieve precise automated pollen recognition to minimize the manual labor and subjectivity associated with human identification. The objective of the study was to evaluate the potential of surface-enhanced Raman spectroscopy (SERS) properties of pollen grain spectra, specifically within the spectral range of 582–1563 cm–1, using the convective assembly combined principal component–canonical discriminant analysis (PC-CDA) classification model. This research aimed to explore the feasibility of using this approach for the automated identification of pollen in the future. This approach facilitates the optimal arrangement of pollen grains and colloidal silver nanoprobes, thereby enhancing SERS spectra reproducibility using the convective assembly sampling method. Pollen grains can be characterized at a microscopic level without the need for purification-based analysis procedures. The findings demonstrate the possibility of rapid and accurate classification of pollen grains with the PC-CDA detection model with a 99.3% sensitivity, 97.6% specificity, and 98.5% accuracy. Research study indicates that the SERS properties of pollen spectra could serve as a promising method for automated pollen identification using the PC–CDA classification model.

Production and characterization of electro-blown nanofibers incorporated with pine pollen for fast-dissolving applications

This study aims to harness the rapid dissolution capability of Polyvinylpyrrolidone (PVP), a versatile and biocompatible polymer, in conjunction with pine pollen, a natural substance rich in antioxidants and offering nutrient-dense advantages for overall health and vitality, for the development of fast-dissolving tablet applications. Employing the electro-blown spinning method, PVP nanofibers were fabricated with pine pollen dust sourced from male pine cones. Through electro-blown spinning (EBS), Polyvinylpyrrolidone (PVP) nanofibrous mats were produced with varying concentrations of Pine pollen (PP) (1,3 and 5 %). Analyses were conducted to assess the characteristics of the produced nanofibers, including morphology, thermal stability, mechanical properties, and surface wettability. Antioxidant tests and α‐glycosidase inhibition activity tests were performed to explore the health benefits of nanofibrous mats. The water solubility of PVP, PVP/1 PP, PVP/3 PP, and PVP/5 PP was measured to be 6.97, 4.74, 3.03, and 6.67 s, respectively. The antioxidant properties and α-glycosidase inhibition activity were preserved in the developed fibers. Notably, the α-glycosidase inhibition activity test demonstrated promising results, suggesting the potential of these fibers in regulating glucose absorption and enhancing glycemic control, highlighting their prospective benefits in diabetes management.

Pollen atlas and morphological analysis of the selected types from southeastern Tibet, China

The accuracy of fossil pollen identification is crucial for understanding past plant diversity, vegetation landscape and associated climate change, while dispersed/fossil pollen assignments heavily rely on how robust modern pollen reference is. There is high species richness in southeastern Tibet, China, however, pollen morphological studies in this area are still poorly documented. Here, we present pollen atlas of 57 species (40 genera, 22 families) collected from the Ranwu Lake Basin. Pollen grains were imaged with light microscope (LM, 100X oil-immersion objective lens) and scanning electron microscope (SEM). All pollen types are ordered and presented according to different aperture types and sculpture patterns, facilitating comparison with fossil pollen. Moreover, we selected some representative species mainly based on potential palaeoecological importance, including Sibiraea (Rosaceae), Koenigia cathayana (Polygonaceae), Stellera chamaejasme (Thymelaeaceae), Hordeum vulgare subsp. vulgare and Poa annua (Poaceae), to discuss their pollen identification characteristics for the first time and assess potential applications in Quaternary palaeoecological interpretation. This study enriches modern pollen atlas for Quaternary pollen analysis in the study area and the adjacent regions. Our results provide robust modern reference in pollen-based reconstruction of vegetation history, palaeoclimate and palaeoenvironment, and tracing pollen signal of local human activities as well.

Buzz pollination: Bee bites and floral vibrations

Certain bees bite tubular anthers while contracting their flight muscles. This floral sonication ejects pollen grains that the bees collect as larval food. Bees bite and buzz simultaneously. A new study shows that where and how they bite is essential for efficient pollen collection.

Evolution of West‐East Contrast in the Subarctic Pacific Gyre During the Plio‐Pleistocene Based on Palynological Evidence at ODP Sites 882 and 887

AbstractFragmentary and contradictory evidence prevents a clear understanding of the possible role of the North Pacific Ocean surface on the ice‐sheet evolution. New palynological data encompassing the Pliocene and Pleistocene at Ocean Drilling Program Site 882 in the northwest Pacific document sea‐surface conditions from dinoflagellate cysts in addition to atmospheric trajectories from pollen grains and spores. The comparison of the Site 882 record with that of Site 887 from the northeast Pacific also permits documenting West to East contrasts across the subarctic North Pacific. The dinocyst assemblages at the two sites indicate strong temperature contrasts until 4.2 Ma, with much warmer conditions in the East. From 4.2 to 3.6 Ma, dinocyst assemblages of both sites are characterized by alternated dominance of the extinct taxa Habibacysta tectata and Impagidinium detroitense suggesting homogenous and cool conditions across the subarctic Pacific gyre. A major transition is recorded in the palynological assemblages at Site 882 around 2.7 Ma. It is marked by the highest occurrence of Habibacysta tectata and high percentages of Filisphaera microornata additionally to thermophilic taxa. Dinocyst record indicates high seasonality and warmer surface conditions due to reinforced stratification, which support the hypothesis of high evaporation at the origin of atmospheric moisture supply to high latitudes. During the last 1.2 Ma, the increase of Operculodinium centrocarpum relative to Nematosphaeropsis labyrinthus is tentatively interpreted as a reinforced influence of the subtropical waters. Hence, we suggest that the warm surface ocean fostered the inception and growth of northwestern North American ice‐sheets during the Pliocene and Pleistocene.

Characterization of Male Flower Induction by Silver Thiosulfate Foliar Spray in Female Cannabis at the Middle Reproductive Stage for Breeding.

Cannabis (Cannabis sativa) is a versatile crop belonging to the Cannabaceae family, and is dioecious, typically with separate male and female plants. The flowers of female plants, especially the trichomes, accumulate relatively higher contents of cannabinoids compared with those of male plants. For this reason, to obtain seeds that are genetically female, it is desirable to induce the development of male flowers on a female plant that produces genetically female haploid gametes. Silver thiosulfate (STS) is a highly effective chemical for male flower induction. We investigated male flower induction in three commercial cultivars of female cannabis (Spectrum303, SuperwomanS1, and CBGambit) regarding the treatment frequency, stage of application, and concentration of STS applied as a foliar spray. All three cultivars showed adequate induction of male flowers in response to 1.5 mM STS applied at the early reproductive stage. In particular, SuperwomanS1 was most highly responsive to induction of male flowers, even when treated with 0.3 mM STS at the early reproductive stage. Treatment with three applications of STS was more effective compared with a single application, but a single application of 1.5 mM STS at the early reproductive stage was sufficient for male flower induction. A single STS application during the middle stage of reproductive growth was inadequate for induction of male flowers. However, 6 weeks after three applications of STS, CBGambit exhibited approximately 54% male flower induction at 0.3 mM STS, Spectrum303 showed approximately 56% induction at 3 mM STS, and SuperwomanS1 yielded approximately 26% induction at 1.5 mM (expressed as percentage of total number of individuals with the induced male flowers). Pollen stainability tests using KI-I2 solution and Alexander's staining showed high pollen viability with over 65% at different single STS concentrations, indicating that pollen grains induced by STS have sufficient viability for the self-pollination. This study demonstrated that different cultivars of cannabis respond diversely to different STS concentrations and highlighted the potential benefits of three STS applications during the middle reproductive stage for cannabis breeding.