Pollen Research Articles

Enhancement of bud dormancy release and development, leaf nutrition, flower and fruit quality of kiwifruit cv. ‘Hayward’ induced by BUD 14 biostimulant

The aim of this research was to investigate the influence of a foliar fertilization program, consisted of the BUD 14 nitrogen-calcium commercial formulation (N: 14% w/w, CaO: 5.5% w/w) as a biostimulant, on bud development percentage, flowering rate, classification of flowers into open, closed and triple, flower and pollen quality traits, fruit quality attributes, and leaf nutritional status of the ‘Hayward’ kiwifruit cultivar. The study was realized during a two-year experimental period in Naoussa, Central Macedonia, Greece. The results showed that BUD 14 induced synchronization in bud development relative to different vegetative stages including initiation of bud expansion, appearance of leaf apices covered by hair and deployment of 2-8 leaves and increased the flowering rate of open flowers. Pedicel length, ovary fresh weight, and dry weight, dry matter and length in female flowers as well as maximum pollen grain diameter and area in polar view in male flowers were significantly enhanced in the BUD 14 treatment. Fruit quality characteristics like average weight and dry mass were significantly augmented, and a 1.5-fold and 2-fold increase was recorded in canes length and number of kiwifruits per cane. In addition, leaf nutrient Ca and Mg concentrations were significantly enhanced, compared to the control. The efficacy of BUD 14 as a more target-oriented and environmentally friendly alternative method of supplying plants with smaller and controlled amounts of nutrients for breaking bud dormancy and improving their development was demonstrated, enhancing flower and fruit quality, leaf nutrition, kiwifruit developmental characteristics, and finally the total production per fruit per tree.

Pollinator behaviour and prevalence of the anther smut Antherospora vindobonensis in its host, the Hungarian two-leaf squill (Scilla vindobonensis).

Anther smuts are fungal diseases that have detrimental effects on the biology of their host plants. We investigated the transmission of Anther smut Antherospora vindobonensis to its host, Scilla vindobonensis under natural and laboratory conditions. Plants flowering early in spring were less vulnerable to disease (∼ 20-30% of plants which appeared early in the season were diseased) than flowers that bloom at the end of the season (∼ 60% of plants which appeared late in the season were diseased) which contradicts the patterns observed for other anther smuts species. Diseased plants showed thicker stems, lower nectar production and smaller flower radius than healthy plants. The disease prevalence in S. vindobonensis was not influenced by plant density. The production of spores in diseased flowers was 125 times higher than the production of pollen in healthy flowers. The number of pollen grains attached to pollinator bodies from healthy plants under controlled conditions was similar to the number of spores attached from diseased plants. Experienced honeybees in the field showed almost identical preferences for healthy plants (65%) over diseased ones, as did naïve bumblebees under controlled laboratory conditions (69%). eDNA metabarcoding revealed that healthy flowers attracted a significantly higher number of arthropod species (M = 6.23, SE = 1.48) than diseased flowers (M = 2.32, SE = 0.31). Strong seasonal differences in the risk of infection suggest that S. vindobonensis solves the trade-off between low pollinator availability and low risk of infection at the beginning of the season and high risk of infection and high pollinator availability at the end of season. By reproducing early in the season, plants can reduce the risk of disease.

PollenNet: A novel architecture for high precision pollen grain classification through deep learning and explainable AI

Pollen grains play a critical role in environmental, agricultural, and allergy research despite their tiny dimensions. The accurate classification of pollen grains remains a significant challenge, mainly attributable to their intricate structures and the extensive diversity of species. Traditional methods often lack accuracy and effectiveness, prompting the need for advanced solutions. This study introduces a novel deep learning framework, PollenNet, designed to tackle the intricate challenge of pollen grain image classification. The efficiency of PollenNet is thoroughly evaluated through stratified 5-fold cross-validation, comparing it with cutting-edge methods to demonstrate its superior performance. A comprehensive data preparation phase is conducted, including removing duplicates and low-quality images, applying Non-local Means Denoising for noise reduction, and Gamma correction to adjust image brightness. Furthermore, Explainable AI (XAI) is utilized to enhance the interpretability of the model, while Receiver Operating Characteristic (ROC) curve analysis serves as a quantitative method for evaluating the model's capabilities. PollenNet demonstrates superior performance when compared to existing models, with an accuracy of 98.45 %, precision of 98.20 %, specificity of 98.40 %, recall of 98.30 %, and f1-score of 98.25 %. The model also maintains low Mean Squared Error (0.03) and Mean Absolute Error (0.02) rates. The ROC curve analysis, the low False Positive Rate (0.016), and the False Negative Rate (0.017) highlight the reliability and dependability of the model. This study significantly improves the efficacy of classifying pollen grains, indicating an important advancement in the application of deep learning for ecological research.

Heat stress during reproductive development inhibits fertilization in olives

In this study, we investigated the effect of heat exposure during olive inflorescence on reproductive development. We hypothesized that male development processes during this period are particularly sensitive to high temperatures. We characterized the development of flowers and inflorescences under natural conditions in the cultivars 'Arbequina' and 'Koroneiki', and defined eight phenological stages, beginning with the emergence of reproductive buds until anthesis (international standard BBCH scale of the phenological inflorescence development phases 53–60). In addition, we examined the response of olive inflorescence and flowering, to two heat scenarios: prolonged exposure to moderately high temperatures and a two-hour concentrated heat shock treatment. Analysis of our data revealed that both treatments had a detrimental effect on the development and functioning of the tapetum, the innermost layer of the anther, which is essential for the development and functioning of pollen. Additionally, we found that the 'Arbequina' cultivar displayed relative tolerance to heat compared to 'Koroneiki' in terms of pollen germinability after heat stress. In contrast to the response of the above cultivars, the 'Souri' exhibited an exceptionally high sensitivity to heat. An assessment of pollen viability after in vitro heat shock treatment of 54 cultivars revealed that pollen from seven varieties, 'Niedda de Oliana', 'Lechín de Sevilla', 'Tonda Oliana', 'Tamir', 'Sigoise', 'Taggiasca', and 'Carrasquenha', showed exceptional tolerance to heat. These cultivars show a greater degree of suitability for cultivation in warm climates, (or in areas susceptible to extreme hot-spells). This study demonstrated that heat has a negative impact on the male reproductive system in olives, during early flower development and in mature pollen grains, which are relatively resistant to heat. Heat stress impaired pollen tube elongation capacity, and germination rate. Additionally, heat stress affected the ultrastructure of the external wall of the pollen grain, the exine, potentially impairing its ability to adhere to the stigma and fertilize the ovule. The sensitivity of olive reproductive capacity to heat is a genotype-dependent trait, allowing for the identification of heat-resistant cultivars for use as pollen donors and for development of new heat-resistant cultivars.

Chromosome Study of Six Populations of Trifolium tumens Stev. ex M. B. in IRAN

Trifolium tumens Stev. ex M. B is a perennial legume with long‐lived and deep rooting from the Vesicaria section in Trifolium genus. It is distributed in Iran. The base chromosome number (x = 8) in the population, confirmed the views of the previous researchers. In this study, the number of chromosomes in the mitotic metaphase stage in the meristematic cells of the root ends were counted in six populations of Trifolium tumens. Also, chloroplast count of stomata guard cells, morphological studies, pollen grain size and flowcytometry were studied in six accessions. Our results showed that this species has ploidy level (2n=16, 2n=32). and the tetraploid state in the species T. tumens is reported. Through flowcytometry, chloroplast count of stomata guard cells and compare the pollen grain, different characters were showed between diploid and tetraploid populations, too. Based on the results, this new cytotype is reported from Iran.

Differential Variability of Maize (Zea mays L.) Inbred Lines to Moisture-stress at Reproductive Stages and DNA Methylation Studies of Identified Contrasting Genotypes under Moisture-Stress Conditions

An investigation was undertaken to assess the effect of moisture stress during the reproductive initiation stage on the quality and quantity of pollen grains produced in eight inbred lines (UASBM22, UASBM13, UASBM09, UASBM11, UASBM06, UASBM14, UASBM02 and UASBM10) under greenhouse conditions in three blocks viz., well-watered, stress I (for 21 days from 28 days after sowing) and stress II (for 22 days from 32 days after sowing). Moisture stress significantly affected the number of pollen grains per anther and other plant growth-related traits. The moisture stress effect was not uniform across inbred lines. The inbred lines UASBM22, UASBM13, UASBM09 and UASBM11 recorded a significant reduction in the total number of pollen grains per anther and an increase in pollen sterility while in inbred lines, UASBM06, UASBM14, UASBM02 and UASBM10, the moisture stress effect was not significant. The changes in the DNA methylation pattern in leaves and immature anthers under moisture stress of the contrasting inbred lines (UASBM06 and UASBM13) were studied through methylation- sensitive random amplification polymorphism. An increase in total DNA methylation level in both leaves and anthers was observed in drought tolerant inbred line, UASBM06 under stress while the increase was only in the leaves of the susceptible inbred line UASBM13. Leaves and anthers of UASBM06 showed hypermethylation compared to UASBM13 in moisture-stress conditions. In maize, increased DNA methylation seems to be an important mechanism associated with drought responses which probably regulates the methylation-sensitive gene expression and acclimation responses in maize.

Reproductive Performance of the Alpine Plant Species Ranunculus kuepferi in a Climatic Elevation Gradient: Apomictic Tetraploids Do Not Show a General Fitness Advantage over Sexual Diploids.

Previous studies on the mountain plant Ranunculus kuepferi concluded that apomictic self-compatible tetraploids have experienced a niche shift toward a colder climate during the Holocene, which suggests a fitness advantage over the sexual, self-sterile diploid parents under cold and stressful high-mountain conditions. However, there is still a lack of information on whether reproductive development would be advantageous for tetraploids. Here, we report on microsporogenesis, megagametogenesis, the dynamics of flower and seed development, and the consequences for reproductive success in a common garden experiment along a 1000 m climatic elevation gradient and in natural populations. Flower buds were initiated in the year preceding anthesis and passed winter in a pre-meiotic stage. Flower morphology differed in the known cytotype-specific way in that tetraploid flowers produced about twice as many carpels and fewer petals, stamens, and pollen grains than diploid flowers. Tetraploids developed precociously aposporous embryo sacs and showed a high rate of developmental disturbances. Sexual seed formation prevailed in diploids and pseudogamous apomixis in tetraploids. Along the elevation gradient, stigma pollen load, pollen performance, and seed output decreased. Combinations of reproductive traits, namely, bypass of meiosis irregularities and uniparental reproduction, might have promoted the vast expansion of apomictic R. kuepferi lines across the European Alps.

Reply to Head's comment on “The Volyn biota (Ukraine) – indications of 1.5 Gyr old eukaryotes in 3D preservation, a spotlight on the `boring billion' ” by Franz et al. (2023)

Abstract. Head et al. (2024) emphasize the importance of the Volyn biota for evolution, especially in the so-called “boring billion”, in a detailed outline about the biological and geological context. However, they question the idea that the Volyn biota represent Precambrian fossils and instead argue that they contain young contaminants of “museum dust”. In addition, they question their biotic origin. We present here a detailed discussion of their points of concern based on presented data, including some additional information. Their points of concern were as follows: One object, shown by Franz et al. (2023a), is similar to a pollen grain, and another object is similar to trichomes; we show indications of fossilization and summarize our arguments against “museum dust”. They question the fossil character of the biota and argue for a biomineralization; we show that the biomineralization in trichomes is distinct from the mineralization of the biota. They missed information about the internal structure; we repeat the presented information about the internal structure in more detail, which is also indicative of fossil material and inconsistent with trichomes. They argue that we did not compare the biota with recent fungi via infrared spectroscopy; since the biota experienced temperatures near 300 °C, we think that a comparison with thermally degraded chitosan is more appropriate. They question the use of strongly negative δ13C as an argument for biotic origin, but we show that, in combination with positive δ15N values and the geological situation, a biotic origin is more likely than abiotic synthesis. In addition, Popov (2023) questioned the age of the Volyn biota, which we postulated as between approximately 1.5 and 1.7 Ga. He argues that the fossils could be Phanerozoic. We will also outline our arguments for the minimum age of 1.5 Ga.

Micromorphological and Phytochemical Evaluation of Heliotropium rariflorum Stocks From Karak, Pakistan.

Micromorphological and phytochemical studies play a major role in quality control and standardization of traditional or herbal medications. In the present research, micromorphological assessment of Heliotropium rarifloum stocks was performed through light and scanning electron microscopies (LM & SEM). The anatomy of leaves, stem and root showed salient histological features. Both surfaces of the leaves had setose glandular trichomes measuring 20-38 × 6-15 µm. The lower epidermis had comparatively a maximum anomocytic stomata (16-35) and stomatal index (12-33). The mature pollen grains were small (74 µm) and spheroidal shaped, with psilate exine (2 μm) sculpturing. Vein termination and vein islet number of the upper epidermis were 5-20 and 5-15, respectively. The palisade ratio of the leaf lamina for the upper and lower epidermis was 2-10 and 2-8. LM and SEM of the powdered samples displayed crystals, phloem fibers, xylem, vessels, sieve tube elements, companion cells, and tracheids. Extractive values determination, fluorescence, and phytochemical analysis were employed for quality control according to the World Health Organization (WHO) guidelines. Phytochemical screening revealed various secondary metabolites. It is suggested that H. rariflorum might be a reliable source of nutrients and secondary metabolites and might be more medically effective. The current findings confirm its standardization and validation.

Holocene hillslope evolution through extreme rainfall induced landslides in the mountainous region of Rio de Janeiro, Brazil: Geochronology and paleoenvironmental evidence

AbstractGeomorphological, geochronological and paleoenvironmental data were integrated to examine how Holocene environmental changes have influenced geomorphic responses, particularly recurrent landslides and colluvial deposition on the steep slopes of the Rio de Janeiro mountains. This study focuses on a pilot hillslope (32°) with a concave‐up topographic hollow and associated shallow translational landslides, enhancing our understanding of how extreme climatic events shaped landscape evolution in the region prior to significant human impact. Recently, the hillslope was reactivated by a shallow landslide triggered by the extreme rainfall event of January 2011, which resulted in over 3600 landslides in the region. Subsequent deep gullying exposed a deposit (>3 m) containing buried, organic‐rich colluvial layers. Comprehensive analysis was conducted on sedimentological, geochronological (AMS 14C), palynological, taphonomic and carbon isotope (δ13C) data from this deposit. The geochronological results indicate that the hillslope's evolution involves recurrent shallow translational landslides throughout the Holocene, with organic colluvial layers dating from 10 148 cal years BP at the base to 663 cal years BP at the top. Charcoal fragments of various sizes suggest frequent paleofires during the Holocene. Palynological and taphonomic analyses reveal post‐fire herbaceous‐shrubby vegetation and ferns (Asteraceae, Poaceae, Alchornea, Baccharis, Celtis and Polypodium), with predominant pollen grains and spores showing mechanical damage indicative of high transport energy and physical stress conditions. The rarefied post‐fire vegetation and pioneer forest genera identified in the deposit are associated with a hydrological and mechanical dynamics that likely created less stable conditions on the slope system, promoting the occurrence of shallow landslides throughout the Holocene.

Preparation of two-dimensional pine pollen derived carbon sheets by rapid microwave carbonization for efficient MCDI desalination

Membrane capacitive deionization (MCDI) has garnered significant attention in recent years due to its ability to effectively mitigate the co-ion effect in traditional CDI desalination processes, thereby substantially enhancing the desalination capacity. In this study, pine pollen with unique natural morphology was used as a biomass precursor, and two-dimensional carbon sheets with hierarchical pore structures were prepared through a one-step rapid microwave carbonization and KOH activation process. Due to its wrinkled two-dimensional morphology, abundant defects and micropores, and chemical composition rich in oxygen-containing functional groups and nitrogen element, the carbon sheets exhibit excellent desalination performance. In the MCDI system (applied voltage of 1.8 V, flow rate of 11 mL min−1, and initial NaCl solution concentration of 700 ppm), an adsorption capacity of up to 89.86 mg g−1 was achieved, and the adsorption rate reached up to 1.50 mg g−1 min−1. Therefore, the pine pollen-derived carbon in this study exhibits outstanding capacitive deionization desalination performance and demonstrates great potential for practical applications.

Notes on the Morphology, Anatomy, Palynology, and Karyology of Onobrychis argaea (Fabaceae), Endemic to Turkey

Onobrychis argaea belonging to the Fabaceae family, is an endangered plant species endemic to Turkey, distributed only in Kayseri Erciyes Mountain. This study represents the first comprehensive investigation into the morphology, anatomy, pollen and seed micromorphology, and chromosome characteristics of O. argaea. The previous description of the species has been expanded and modified. The pith of the root is covered with xylem tissue. In the stem cross-section, the protective tissue is periderm in the woody part and epiderm in the herbaceous part. The leaflets are amphistomatic and equifacial. The pollen grains are radially symmetric, isopolar, tricolpate, with prolate shape and reticulate-microreticulate ornamentation. The seeds are reniform, yellowish-brown, suboblate, and exhibit rugulate surface ornamentation. The number of somatic chromosomes in O. argaea is 2n = 14. The karyotype formula of this species consists of seven median chromosomes.

Neural stimulation and modulation with sub-cellular precision by optomechanical bio-dart

Neural stimulation and modulation at high spatial resolution are crucial for mediating neuronal signaling and plasticity, aiding in a better understanding of neuronal dysfunction and neurodegenerative diseases. However, developing a biocompatible and precisely controllable technique for accurate and effective stimulation and modulation of neurons at the subcellular level is highly challenging. Here, we report an optomechanical method for neural stimulation and modulation with subcellular precision using optically controlled bio-darts. The bio-dart is obtained from the tip of sunflower pollen grain and can generate transient pressure on the cell membrane with submicrometer spatial resolution when propelled by optical scattering force controlled with an optical fiber probe, which results in precision neural stimulation via precisely activation of membrane mechanosensitive ion channel. Importantly, controllable modulation of a single neuronal cell, even down to subcellular neuronal structures such as dendrites, axons, and soma, can be achieved. This bio-dart can also serve as a drug delivery tool for multifunctional neural stimulation and modulation. Remarkably, our optomechanical bio-darts can also be used for in vivo neural stimulation in larval zebrafish. This strategy provides a novel approach for neural stimulation and modulation with sub-cellular precision, paving the way for high-precision neuronal plasticity and neuromodulation.

Increased rupture of cypress pollen type due to atmospheric water in central and southeastern Spain

This study aims to investigate the meteorological variables determining Cupressaceae pollen grain disruption in the environment. A parallel sampling of pollen grains and disrupted Cupressaceae pollen grains was performed in six cities using two Spanish aerobiological networks. The pollen concentrations, disrupted pollen concentrations, percentage of disrupted pollen and number of days when the percentage of disrupted pollen was above or equal to 50 % were quantified during two pollen seasons. The concentrations were determined following the standardised method EN 16868. Results show that the concentrations of pollen grains and disrupted pollen grains were not determined by geographical features and rarely by bioclimatic variables or indexes but by the ornamental use of the specimens in the vicinity of the pollen sampler, highlighting the possibility of using management practices to reduce exposure to allergens in the cities. African dust outbreaks coincided with higher concentrations of pollen grains and disrupted pollen grains, but the reduced percentage of disrupted pollen grains pointed to a non-causal relationship with long-distance transport. The effect of wind and maximum gusts remained negligible. The triggering factor for pollen disruption was the amount of water in the atmosphere, mainly reported as relative humidity. Rainfall increased the effect of disruption due to pollen grain swelling caused by its wash-out effect. The higher the relative humidity, the higher the disrupted pollen concentrations. This aligns with the mechanism of Cupressaceae reproduction since the family needs a water medium in the form of pollination droplets for the pollination tube to develop and the pollen grain to perform its biological function. Therefore, people that develop allergic symptoms to Cupresaceae pollen should avoid exposure during days with high relative humidity in the main pollen season.

GENESIS OF THE UPPER PLEISTOCENE GRAVEL FROM THE ABESINIJA PIT SE FROM ZAGREB (CROATIA)

Polymictic gravels exploited in the vicinity of Rugvica, SE from Zagreb, comprise clasts of various lithology, colour, shape, and size. Pebbles are composed of sedimentary, volcanic and, sporadically, metamorphic rocks. During the field work we recognized fossils in the abundant carbonate pebbles. Most of the carbonate clasts are rounded, discoidal in shape, varying in colour from white to dark grey, almost black. Pebbles were measured by a calliper and petrographic thin sections were prepared from fossiliferous pebbles. Numerical analyses pointed to some minor differences in their shape and size, but micropaleontological analyses revealed clasts of Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene and Neogene age. Most of the Mesozoic and Cenozoic clasts originate from the two local mountain areas (Medvednica Mt. and Samobor Hills), with part of the Jurassic-Cretaceous pebbles possibly derived from SW Slovenia. Irregularly shaped and sometimes poorly rounded clasts of the Paleogene/Neogene ages seem to be abruptly transported to short distances by torrents or streams. The most enigmatic were the clasts of Carboniferous-Permian age. The nearest Palaeozoic outcrops occur upstream in Central Slovenia, but some fossils point to the even longer transport route, from the Karavanks in the upper flow of the Sava River. Gravels are overlain by fine-grained lake sediments and peat coal. Peat comprises significant amount of pine pollen, pointing to the warming period within the Late Pleistocene, which was additionally confirmed by the radiocarbon dating.

Morphological Changes in Allergenic Pollen as a Bioindicator

Since the anther opens and the pollen grains travel in the atmosphere, they can come into contact with solid and gaseous particles, and the exine can become contaminated with various adherent particles. Pollen and solid particles are among the most common triggers of bronchial asthma. Increased allergenicity of pollen grains will be determined by chemical reactions between pollutants and pollen, as well as non-specific modulation of the mechanisms of synthesis of many proteins, lipids and enzymes in response to environmental stress due to urbanization and climate change. This situation seriously complicates the identification of pollen to a taxon during traditional monitoring and further complicates the calculation and interpretation of the results obtained during research and automatic determination. To classify tetramorphic pollen from aerobiological samples and explain the mechanism of the identified changes. Determination of mutagenic contamination and a method for integral assessment of pollen viability and damage under a light microscope. Pollen from aerobiological samples was examined under a scanning electron microscope (Hitachi): a high-power imaging technique that uses electron beams to create detailed images of the ultrastructure of pollen grains. Unidentified, tetramorphic pollen from aerobiological samples from sites with varying degrees of contamination can be conditionally classified into 4 types: 1) shapeless lumps of sporopollenin with various outgrowths, cracks and cavities that arose during pollen ontogenesis; 2) atypical ornamentation of sculpture, such as large tubercles - swellings with a smooth surface; 3) atypical form, but with partially preserved sculpture, where in places species-specific features can be identified and pollen can be identified to a taxon; 4) conglomerates. The study of the vitality (viability) and damage of the cocksfoot pollen under a light microscope from observation points with different anthropogenic loads showed the dependence of these indicators on the level of pollutants: with their increase, viability decreases, although it remains quite high. The data obtained are important for assessing allergenic pollen as a bioindicator of environmental changes. An integrated assessment of the enzymatic activity of pollen and the degree of its damage can be used for the purposes of bioecological monitoring.

Amaranthaceae Pollen Trends in the Air

Understanding the trends of airborne pollen allergens is of great importance given the high prevalence and socioeconomic impact of pollen-related allergic diseases globally. To study the morphological features of Amaranthaceae pollen, assess its contribution to the aerobiological situation in the city of Karakol and identify periods of increased concentration in order to improve the diagnosis and prevention of pollinosis symptoms in patients. Aerobiological sampling using a Lanzoni pollen trap was carried out from April to October over a three-year period (2015–2017) in Karakol city. Pollen identification and differential counting were performed according to current standard methodology and specially developed guides and atlases. Pollen characteristics of 4 Amaranthaceae species were visualized using scanning electron microscopy (Hitachi) to provide a detailed understanding of the surface structure and ornamentation of pollen grains. The decadal curve of Amaranthaceae pollen concentration in Karakol is unimodal, with often overlapping quantitative characteristics: 6615 (2nd decade of August 2015), 1326 (1st decade of 2016), 444 pollen grains / m3 (1st decade of 2017). At the same time, strong interannual variability of atmospheric pollen levels was observed, depending both on the pollen production of the plants themselves and on meteorological parameters, especially temperature and precipitation, changes in the traditional farming system. The response of summer-flowering Amaranthaceae weeds to climate change was demonstrated, which consists in a decrease in the annual pollen index, which corresponds to the global trend. Peak concentrations of Amaranthaceae pollen many times exceeded clinical threshold values in the air. On the surface of the Bassia scopariapollen exine, the ultrastructure study revealed the smallest (1.5-2.0 μm) granules of sporopollenin or orbicules (Ubisch bodies), which play a role in the spread of allergens. The obtained data are important in terms of increasing public awareness of the dominant pollen of the Amaranthaceae family, optimizing diagnostics, treatment and prevention of pollinosis.

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.