Surface Of Pollen Grains Research Articles

Combatting the antigenicity of common ragweed pollen and its primary allergen Amb a 1 with cold atmospheric pressure air plasma

Airborne allergens, especially those originating from various types of pollen, significantly compromise the health and well-being of individuals on a global scale. Here, cold atmospheric pressure plasma (CAP) created in ambient air was used to treat highly allergenic and invasive Ambrosia artemisiifolia pollen. Immunoassays were used to evaluate the impact of CAP on the principal A. artemisiifolia allergen Amb a 1, demonstrating that > 90 % reduction in antigenicity could be achieved. Chemical analyses using Fourier Transform infrared revealed that CAP induced significant alterations to proteins on the surface of pollen grains, resulting in a 43 % increase in the amide I peak area and a 57 % increase in the amide II peak area. These findings were corroborated by Raman and X-ray photoelectron spectroscopy, which indicated that the protein modifications induced by CAP were due to carbonylation and nitration/nitrosylation processes. Beyond protein transformations, CAP also induced notable oxidation and modification of lipid-like compounds, polysaccharides and sporopollenin. Evident transformations at the chemical level translated into morphological changes at the grain surface, manifesting as increased roughness via significant outer-layer etching. These findings underscore the potential of CAP technology as a viable approach for mitigating against the allergenicity of pollen, providing a deeper understanding into the underlying chemical mechanisms.

Morphological study of sexual reproductive disorders in Ligusticum chuanxiong

Chuanxiong Rhizoma is a well-known Sichuan-specific herbal medicine. Its original plant, Ligusticum chuanxiong, has been cultivated asexually for a long time. L. chuanxiong has sexual reproductive disorders, which restricts its germplasm innovation. However, there is little research on the reproductive system of L. chuanxiong. This study is based on a comparative anatomical research approach, using morphological dissection, paraffin sectioning, staining and compression, and combined with scanning electron microscopy technology, to observe and compare the flowers, fruits, and seeds at various stages of reproductive growth of L. chuanxiong and its wild relative L. sinense. The results showed that the meiosis of pollen mother cells is abnormal in L. chuanxiong anthers, and the size and number of microspores are uneven and inconsistent in the tetrad stage. tapetum cells are not completely degenerated during anther development. During the pollen ripening stage, there are fine cracks in the anther wall, while most anthers could not release pollen normally. The surface of mature pollen grains is concave and partially deformed, and the pollens are all inactive and cannot germinate in vitro. The starch, polysaccharides, and lipids in the pollen were insufficient. The filaments of L. chuanxiong are short at the flowering stage and recurved downward. Double-hanging fruits were observed in the fruiting stage, being wrinkled; with shriveled seeds. Compared with L. sinense at the same stage, the anthers of L. sinense developed normally, and the pollen grains are vigorous and can germinate in vitro. The double-hanging fruits of L. sinense are full and normal; at the flowering period, the filaments are long and erect, significantly higher than the stigma. Mature blastocysts are visible in the ovary of both L. chuanxiong and L. sinense, and there is no significant difference in stigmas. The conclusion is that during the development of L. chuanxiong stamens, the meiosis of pollen mother cells is abnormal, and tetrad, tapetum, filament and other pollen structures develop abnormally. L. chuanxiong has the characteristic of male infertility, which is an important reason for its sexual reproductive disorders.

Application of Scanning Electron Microscopy to Study Morphological and Anatomical Features of Sea Buckthorn Leaves

Introduction. Scanning electron microscopy is a modern method that allows us to study not only the morphological features of objects, but also to conduct micro-X-ray structural analysis. Currently, the method is being actively introduced into the study of biological objects (including plant ones). Sea buckthorn (Hippophaë rhamnoides L.) leaves are a non-pharmacopoeial type of medicinal plant raw materials. Further study of the morphology, anatomy and phytochemical composition of leaves can contribute to the production of new, including combined, medicines, which will require the development of a pharmacopoeia article for this medicinal plant raw material.Aim. The aim of the study was to study the morphological and anatomical features of sea buckthorn leaves by scanning electron microscopy.Materials and methods. The object of the study was dried whole leaves of sea buckthorn (Hippophaë rhamnoides L.), collected in the Voronezh region in 2021 during the period of mass fruit maturity. To carry out the study by scanning electron microscopy, pieces of leaves were previously sprayed with gold on an automatic spraying unit Q150R ES (Quorum Technologies Ltd., United Kingdom) to increase conductivity. Micrographs were obtained using an electron microscope JSM-6510LV (JEOL Ltd., Japan).Results and their discussion. The morphology and some features of the anatomical structure of sea buckthorn leaves were studied and the main microdiagnostic signs (surface character, types of trichomes, the presence of stomata) were clarified. The content of elements (silicon, potassium, aluminum, carbon and calcium) was determined during the microrentgenostructural analysis. Micrographs of pollen grains of the plant were obtained, the presence of the element iron in them was established.Conclusion. For the first time, the method of scanning electron microscopy was used to study the morphological and anatomical features of sea buckthorn leaves. The main diagnostic signs of leaves and their location have been clarified. It has been established that carbon predominates in the composition of the raw material elements, and calcium also accumulates. The accumulation of aluminum, silicon and potassium in numerous hairs densely covering the upper, and especially the lower, surfaces of the leaf blade is assumed. The morphology of the surface of pollen grains of sea buckthorn, having a spherical shape with a spiny shell, has been established. Pollen grains, in addition to carbon, are characterized by the accumulation of iron and silicon.

On the exine ultrastructure of fossil ginkgoaleans: In situ pollen of Sorosaccus Harris

The morphology and exine ultrastructure have been studied of pollen grains from pollen cones of Sorosaccus sibiricus Prynada from the Ust’-Baley (Aalenian, Siberia), Sorosaccus sp. from the Vladimirovka (Aalenian-Bajocian, Siberia), and S. ex gr. sibiricus Prynada from the Tyrma (Tithonian–Berriasian, Russian Far East) localities. The pollen grains are boat-shaped and monosulcate. A finely granulate pattern is discernible under high magnification of light microscope in pollen grains from Vladimirovka and Tyrma; SEM shows that this pattern is formed by flat verrucae. TEM shows that sculptural elements are present on the surface of pollen grains from Ust’-Baley, although it is not evident in LM and SEM. By previous data on modern and fossil members, we believed that ginkgoalean pollen grains can be differentiated from similar boat-shaped monosulcate pollen of other affinities by a ratio of ectexinal sublayers (a thick homogeneous tectum, a thin infratectum of one row of structural elements, and a thin foot layer) in combination with an ectexine that is greatly reduced in the aperture region. Freshly obtained data have revealed another set of characters, with a less prominent tectum by comparison to underlying sublayers, an infratectum with small granules within the alveoli, and a prominent verrucate surface pattern that is distinguishable even in transmitted light. Ginkgoaleans are characterized by more than one set of ultrastructural characters of the exine.

Quantifying the Influence of Pollen Aging on the Adhesive Properties of Hypochaeris radicata Pollen.

Simple SummaryPollination is the transfer of pollen from a plant’s male part (anther) to the corresponding female part (stigma). It is a fundamental biological process that ensures plant reproduction. Most studies investigate pollination from a biological perspective, but the underlying physical processes are poorly understood. Many plants rely on insects to transport pollen and the forces with which pollen adhere to insects and floral surfaces are fundamental for successful pollination. We quantified pollen adhesion by measuring the forces necessary to detach Hypochaeris radicata (catsear, a common insect-pollinated plant) pollen from glass and studied for the first time how the adhesion forces change with pollen aging. Our results show that newly formed adhesion bonds between H. radicata pollen and glass are stronger for fresh pollen than for old ones. On the other hand, when H. radicata pollen age in contact with glass, the adhesion between pollen and glass strengthens over time. These effects are probably caused by the viscous liquid covering most pollen (pollenkitt) changing its viscoelastic properties as it dries.Although pollination is one of the most crucial biological processes that ensures plant reproduction, its mechanisms are poorly understood. Especially in insect-mediated pollination, a pollen undergoes several attachment and detachment cycles when being transferred from anther to insect and from insect to stigma. The influence of the properties of pollen, insect and floral surfaces on the adhesion forces that mediate pollen transfer have been poorly studied. Here, we investigate the adhesive properties of Hypochaeris radicata pollen and their dependence on pollen aging by quantifying the pull-off forces from glass slides using centrifugation and atomic force microscopy. We found that the properties of the pollenkitt—the viscous, lipid liquid on the surface of most pollen grains—influences the forces necessary to detach a pollen from hydrophilic surfaces. Our results show that aged H. radicata pollen form weaker adhesions to hydrophilic glass than fresh ones. On the other hand, when a pollen grain ages in contact with glass, the adhesion between the two surfaces increases over time. This study shows for the first time the pollen aging effect on the pollination mechanism.

A peptide-mediated, multilateral molecular dialogue for the coordination of pollen wall formation

The surface of pollen grains is reinforced by pollen wall components produced noncell autonomously by tapetum cells that surround developing pollen within the male floral organ, the anther. Here, we show that tapetum activity is regulated by the GASSHO (GSO) receptor-like kinase pathway, controlled by two sulfated peptides, CASPARIAN STRIP INTEGRITY FACTOR 3 (CIF3) and CIF4, the precursors of which are expressed in the tapetum itself. Coordination of tapetum activity with pollen grain development depends on the action of subtilases, including AtSBT5.4, which are produced stage specifically by developing pollen grains. Tapetum-derived CIF precursors are processed by subtilases, triggering GSO-dependent tapetum activation. We show that the GSO receptors act from the middle layer, a tissue surrounding the tapetum and developing pollen. Three concentrically organized cell types, therefore, cooperate to coordinate pollen wall deposition through a multilateral molecular dialogue.

Quantitative assessment of coagulation of atmospheric particles onto airborne birch pollen grains

The coagulation of airborne particles on the surface of allergenic pollen grains is poorly described in the literature. However, particles deposited on the surface of pollen grains could have an effect on allergy and its symptoms. Observations of pollen surface alterations reported in the literature are either qualitative or are tainted by sampling artifacts that overestimate surface particulate pollution. Birch pollen grains (BPGs) were sampled in the atmosphere during pollination to quantitatively assess the extent of particulate deposition on allergenic pollen surfaces. Airborne PGs were collected with a cascade impactor ensuring no sampling artifact unlike pollen samplers usually used in this type of study. Counting, sizing and elemental analysis of particles adhering on pollen surfaces were performed by SEM/EDX. 68% of PGs did not carry any particle on their visible surface while the remaining 32% had between 1 and 16 particles on their surface. On average, polluted BPGs carried 2 ± 1 particles, representing an average surface coverage of 0.95%. We hypothesized that the main coagulation process was particle deposition by gravitational settling. Collision velocity calculations indicate that coagulation due to gravitational settling is prevalent under typical pollination atmospheric conditions. However, the effects of electric charges carried by pollen are largely unknown and may significantly alter coagulation rates. The presence of particle-polluted allergenic pollens appears to be common in the urban atmosphere, even under low air pollution conditions. The impact of chemical pollution of BPGs due to the presence of particulate matter (including soot particles) remains relatively unknown, both on the allergy and on the reproductive capacity of the trees.

Comparison of the characterization of allergenic protein 3 (Pla a3) released from Platanus pollen grains collected in Shanghai during the spring of 2019 and 2020.

Due to the COVID-19 pandemic in early 2020, large-scale industrial production has been stagnant and reduced, the urban air quality has been greatly improved. It provided an excellent opportunity to explore the effects of air pollutants on the sensitization of pollen allergen proteins in the environment. Platanus pollen grains sampled in the spring of 2019 and 2020 were used for detailed characterization and analysis. Scanning electron microscopy, Fourier transform infrared, X-ray spectroscopy (XPS), trypan blue staining, and western blot analysis were employed to characterize Platanus pollen protein released from pollen grains. Our data showed that the viability of the pollen grains in 2019 was lower compared that in 2020, and the pollen grains collected in 2019 had a higher absorption peak of protein functional groups. The XPS spectra assay result demonstrated that the binding energy of the high-resolution components had not variation on the surface of pollen grains, but relative content of nitrogen and peptide chain in the pollen grains sampled in 2019 were higher than in 2020. These results suggested that more protein in the pollen grains was released onto the surface of pollen grains. In addition, western blot assay showed that the expression of Pla a3 protein in pollen grains sampled in 2019 was significantly higher than that in 2020, revealing that air pollutants could enhance the expression of Pla a3 proteins in Platanus pollen.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10453-021-09731-6.

Abnormal anther development leads to lower spikelet fertility in rice (Oryza sativa L.) under high temperature during the panicle initiation stage

BackgroundDecreased spikelet fertility is often responsible for reduction in grain yield in rice (Oryza sativa L.). In this study, two varieties with different levels of heat tolerance, Liangyoupeijiu (LYPJ, heat susceptible) and Shanyou63 (SY63, heat tolerant) were subjected to two temperature treatments for 28 days during the panicle initiation stage in temperature/relative humidity-controlled greenhouses: high temperature (HT; 37/27 °C; day/night) and control temperature (CK; 31/27 °C; day/night) to investigate changes in anther development under HT during panicle initiation and their relationship with spikelet fertility.ResultsHT significantly decreased the grain yield of LYPJ by decreasing the number of spikelets per panicle and seed setting percentage. In addition, HT produced minor adverse effects in SY63. The decreased spikelet fertility was primarily attributed to decreased pollen viability and anther dehiscence, as well as poor pollen shedding of the anthers of LYPJ under HT. HT resulted in abnormal anther development (fewer vacuolated microspores, un-degraded tapetum, unevenly distributed Ubisch bodies) and malformation of pollen (obscure outline of the pollen exine with a collapsed bacula, disordered tectum, and no nexine of the pollen walls, uneven sporopollenin deposition on the surface of pollen grains) in LYPJ, which may have lowered pollen viability. Additionally, HT produced a compact knitted anther cuticle structure of the epidermis, an un-degraded septum, a thickened anther wall, unevenly distributed Ubisch bodies, and inhibition of the confluent locule, and these malformed structures may be partially responsible for the decreased anther dehiscence rate and reduced pollen shedding of the anthers in LYPJ. In contrast, the anther wall and pollen development of SY63 were not substantially changed under HT.ConclusionsOur results suggest that disturbed anther walls and pollen development are responsible for the reduced spikelet fertility and grain yield of the tested heat susceptible variety, and noninvasive anthers and pollen formation in response to HT were associated with improved heat tolerance.

Morphogenesis of the sporoderm of Pollinia of Anoectochilus roxburghii

The pollen grains of Anoectochilus roxburghii aggregate in pollinia. The aim of this study was to analyse the structural characteristics of pollinium development in A. roxburghii. Features of the pollinia begin to form in the sporogenous cells, in which some cell walls begin to differentiate to form the outline of the pollinia. During development of the microspore mother cells (MMCs), the nucleus and organelles penetrate the cell walls (cytomixis) between MMCs within a pollinium, but not between the MMCs among different pollinia. A thick callose wall forms on the surface of the pollinia, but not between MMCs inside the pollinium. After meiosis, a sporopollenin exine forms on the surface of the pollinia, but not on the surface of pollen grains inside the pollinium. The mature pollen of A. roxburghii is bicellular and consists of a vegetative cell and a generative cell.

Organic and aqueous extraction of lipids from birch pollen grains exposed to gaseous pollutants.

The lipid fraction of birch pollen grains (BPGs) is not yet fully described, although pollen lipid molecules may play a role in the allergic immune response. The mechanisms by which atmospheric pollutants modify allergenic pollen grains (PGs) are also far from being elucidated despite high potential effects on allergic sensitization. This work is a contribution to a better description of the lipid profile (both external and cytoplasmic) of BPGs and of alterations induced by gaseous air pollutants. Several lipid extractions were performed using organic and aqueous solvents on BPGs following exposure to ozone and/or nitrogen dioxide and under conditions favoring the release of internal lipids. Ozone reacted with alkenes to produce aldehydes and saturated fatty acids, while nitrogen dioxide was shown to be unreactive with lipids. NO2 exhibited a protective effect against the reactivity of alkenes with ozone, probably by competition for adsorption sites. The decreased reactivity of ozone during simultaneous exposure to NO2/O3 raised the possibility of a Langmuir-Hinshelwood mechanism. Oxidation reactions induced by exposure of BPGs to ozone did not substantially modify the extraction of lipids by aqueous solvent, suggesting that the bioaccessibility of lipids was not modified by oxidation. On the contrary, the rupture of PGs appeared to be a key factor in enhancing the bioaccessibility of bioactive lipid mediators (linoleic and α-linolenic acids) in an aqueous solution. The internal lipid fraction of BPGs has specific characteristics compared with external lipids, with more abundant hexadecanoic acid, tricosanol, and particularly unsaturated fatty acids (linoleic and α-linolenic acids). Several mechanisms of action of gaseous pollutants on allergenic pollen were identified in this study: gaseous air pollutants can (i) modify the external lipid fraction by reactivity of alkenes, (ii) adsorb on the surface of PGs and be a source of oxidative stress after inhalation of PGs, and (iii) promote the release of cytoplasmic bioactive lipids by facilitating pollen rupture.

Amaranthaceae pollen grains as indicator of climate change in Lublin (Poland)

Previous studies have demonstrated that plants are a very good indicator of global environmental variations. The responses of many plant species to climate change are confirmed by aerobiological research. This paper presents an analysis of many parameters of pollen seasons in the Amaranthaceae family based on measurements of pollen concentrations in atmospheric air. Pollen samples were collected with the volumetric method at a sampling site in Lublin (Poland) in 2001–2019. The obtained data were verified using statistical analyses. Moreover, the presence of pollenkitt on the pollen grain surface was examined in fresh anthers using scanning electron and light microscopes, since there are some difficulties in identification of Amaranthaceae pollen grains deposited on microscopic slides in aerobiological analysis.The pollen season in Amaranthaceae began on average on June 23 and ended on October 5, i.e. it lasted 105 days. The peak value and annual pollen sum were characterized by the highest variability in the study years in comparison with other season characteristics. The annual pollen sum was in the range from 183 to 725. Maximum concentrations were most often recorded in the second half of August, which is associated with the greatest risk of development of pollen allergy symptoms in sensitive subjects during this period. The results obtained in the 19-year study revealed that the pollen seasons began 14 days earlier. Similarly, the end of the season was accelerated by 24 days. The response of these plants to climate change also include the reduced pollen production by representatives of this family, which was manifested by a decrease in the annual sum of daily airborne pollen concentrations, on average by 35%, and a reduction in the maximum pollen concentration, on average by more than 60%. We found that temperature in May and June had an effect on pollen release, and relative air humidity in May influenced pollen concentrations. We noted significant similarities in the pollen release rate during the last 8 years of the study. The scanning electron microscopy examinations showed that the pollen grain surface in the representative of this family was covered completely or partially with pollenkitt. Hence, the apertures characteristic for pollen in this family were poorly visible. The presence of pollenkitt on the surface of these polyaperturate pollen grains may play an important role in preventing water loss during pollen migration in the air. Our research has demonstrated the response of plants flowering in summer to climate change. The results not only have practical importance for public health in the aspect of allergy risk but can also help to assess environmental changes.

Nutritional and techno-functional properties of monofloral bee-collected sunflower (Helianthus annuus L.) pollen

The aim of this study was to examine nutritional (total lipid, carbohydrate, protein and ash content, fatty acids and protein profile) and techno-functional properties of monofloral bee-collected sunflower pollen (Helianthus annuus L.). The content of water, total protein, carbohydrate, lipid and ash was 24.99, 14.36, 82.01, 1.62 and 2.01 g/100g DW, respectively, with the total energy value of 400.06 kcal/100 g DW. The fatty acid profile revealed the presence of five fatty acids with the stearic acid as dominant one (31.4%) followed by α-linoleic (20.7%), pentadecanoic (18.2%), heneicosanoic (17.1%) and palmitic (12.5%) acids. FTIR analysis of bee pollen grains confirmed the presence of the main pollen chemical constituents such as proteins, water, carbohydrates and lipids, but also the presence of sporopollenin and polyphenols. Raman spectroscopy analysis indicated that the surface of pollen grains was rich in carotenoids. Low protein (3.64 g/100g DW) but high carbohydrate (77.09 g/100 g DW) solubility of bee pollen was observed. The good emulsifying properties (ESI, 19.98 min; EAI, 80.54 m2/g) and excellent oil (2.43 g/g DW) but poor water (0.87 g/g DW) absorption capacities were also registered. On the other hand, the sunflower bee pollen did not show foaming properties. These findings indicate to its applicability as useful nutritional, lipophilic and anti-foaming food ingredients.

Evaluation of hirst-type sampler and PM10 impactor for investigating adhesion of atmospheric particles onto allergenic pollen grains

Hirst-type sampler (HTS) is the standard equipment for pollen sampling while cascade impactors are commonly used for particulate matter (PM) samplings. In this work, we investigated the feasibility of using such devices to reliably assess the atmospheric PM adhesion onto pollen grains (PGs). Birch PGs were deposited on sampling substrates and then exposed to ambient PM in each type of sampling device operating simultaneously. In the HTS, the surface of PGs was significantly polluted with PM during sampling (93.5% of polluted PGs with on average 4 particles per PG with a mean diameter of 2.2 µm). A modified entrance slit was tested and proved to significantly reduce the PM sampling artifact (28% of polluted PGs), although not completely canceling it. In contrast, in the PM10 impactor, all PGs remained free from particulate pollutants. We concluded that the PM pollution of PGs reported in previous studies using a HTS may be overestimated. While PG samplings using a HTS might provide insights into the co-exposure to allergenic pollen and other ambient PM, a size-selective aerosol sampler proves to be more appropriate for a reliable assessment of the extent of PM pollution of airborne pollen in order to give a realistic depiction of the physical and chemical state of ambient PGs that could be inhaled.

Pollen Beads: A New Carrier for Propolis Active Compounds.

Pollen and propolis are two bee products with highly health promoting properties. But there are some limitations of raw propolis usage not only in daily consumption but also in putting it in food formulations. Propolis should be extracted to convert it into consumable form and ethanol is the first choice as a solvent. But ethanol consumption, either in health-wise or religious aspect, is one of the factors limiting the usage of propolis extract. The strong taste and strong smell of propolis are other factors. The immobilization of propolis active compounds could be a tool for overcoming either all or some of these factors. This study was aimed at the immobilization of propolis active constituents on the surface of whole pollen grains. Chemical composition of raw propolis was determined by using GC-MS technique. Total phenolic content and antioxidant activity of the samples were measured spectrophotometrically. The release property of the beads was determined. Immobilization efficiency was 53%. Total phenolic and flavonoid content of pollen, propolis and pollen-propolis beads were measured. It was determined that pollen-propolis beads contain more phenolics than pollen and propolis itself. Ferric reducing activity of the samples was also investigated and pollen-propolis beads showed better activity. Release behavior of pollen and pollen-propolis beads was studied in simulated digestive systems. Better release properties of pollen-propolis beads were achieved in all tested systems as well. These findings support the immobilization of propolis active compounds on the surface of whole pollen grains. It could be concluded that the product obtained, pollen-propolis beads, could be considered as a more valuable healthy product since the synergistic action of pollen and propolis.

Pollen morphology of some species of the genus Quercus L. (Fagaceae) in the Southern Caucasus and adjacent areas

The palynomorphology of 19 modern species of the genus Quercus L. native to Armenia and adjacent regions, including the Caucasus and Transcaucasia, the Mediterranean region (especially Turkey), as well as Iran, Iraq and Afghanistan, was studied using light microscopy (LM) and scanning electron microscopy (SEM). The work revealed two main types of apertures (3-zonocolpate, 3-zonocolp-porate) as well as six morphological types of pollen based on three main types of exine ornamentation (tuberculate, verrucate, rugulate). We suggest that two main groups of exine ornamentation developed from a common initial type. The first group covers all species of the subgenus Quercus and also Q. suber and Q. alnifolia of the subgenus Heterobalanus. The second group is limited to the morphological type Q. ilex (species Q. ilex, Q. coccifera, subgenus Heterobalanus). On the other hand, the presence of widespread interspecific and introgressive hybridization within the genus Quercus indicates an ongoing process of speciation. This also has an effect on pollen features, which are very similar in a number of species but also vary in individual samples even within the same species. The morphological uniformity of the pollen surface (especially for the subgenus Quercus), the presence of islets of secondary sporopollenin on the surface of pollen grains, as well as orbicules in anthers, do not indicate general primitiveness of representatives of this genus but most likely denote a relatively high degree of speciation activity within this group.

The Biology of Pomegranate Pollen: All about Formation, Morphology, Viability, Germination and Events relating to Sperm Nuclei

Investigation of pollen biology (i.e. morphology, viability, germination capacity, development of pollen tube and sperm nuclei) of pomegranates, an andromonoecious species, was aimed in this study with the aid of microscopy. Pollens were collected from the Punica granatum L. cv. ‘Caner II’ at different phenological stages. Morphological features showed that the pollen is prolate with smooth exine surface. Viability was higher in the staminate flowers but germination capacity was better in the bisexuals. Pollen germination begins after it leaves the microsporangium. During pollen tube elongation, the pollen cytoplasm, vegetative nucleus and generative cells are transported within the pollen tube. Before entering the pollen tube, the generative cell undergoes mitosis and form two haploid generative cells. Differences in pollen viability and germination ratio of the flower types were found to be insignificant. Polar length was maximum (28.5 μm) in both sexual morphs and minimum (26.8 μm) in the perfect flower. The width of pollen grains ranged from 15.9 μm to 17.1 μm in both types. Perfect and functional male flowers had small pollen (15.9-27.3 μm) with grooves on the surface without perforations. The surface displayed regular continuities where it was between the protrusions. The surface of pollen grains from both of flowers was striate, with more parallel longitudinal ridges in functional male flower. The pollen from both sexes is about the same size. These findings not only provide information on basic features of pomegranate pollen and its pollination biology, but also can help understand breeding and decide strategies to develop better cultivars.

Atmospheric particulate matter adhesion onto pollen: a review

From anther dehiscence to its atmospheric journey, airborne pollen grains can come into contact with other particulate matter (PM) and the external wall of pollen grains can be polluted by adhered atmospheric particles. Pollen and PM are some of the most common asthma triggers. The aim of this review was to discuss literature reporting pollen–particle complexes in the outdoor environment so their potential role in enhancing the risk of allergy could be examined. Twenty-five studies report pollen–particle complexes observed in outdoor conditions. PM adhesion onto the pollen surface was investigated in the literature by three different experimental approaches: direct collection from anthers, bulk exposure of pollen to PM in polluted areas, and direct sampling of airborne pollen during pollination. Four processes are proposed to explain deposition of PM on the surface of pollen grains: sticking of particles to anthers and pollen during dehiscence, airborne pollen-particles coagulation, wet and dry scavenging of pollen and particles, and co-deposition of PM and pollen in the respiratory system. Despite potential adverse health effects, the magnitude of pollution of pollen by PM is poorly understood. To address this issue, we suggest the following guidelines for research: (1) Possible artifacts during sampling and handling of anthers must be carefully avoided; (2) Control pollen grains (i.e. non-polluted) should be carefully selected; (3) A better knowledge of pollen atmospheric deposition and resuspension is needed; (4) The health effects of pollen-particles complexes need more attention regarding symptoms and allergic sensitization; (5) Use of individual pollen samplers could give a depiction of the degree of pollution of pollen that is actually inhaled.

Infrared drying of bee pollen: effects and impacts on food components

Infrared radiation drying being one of the innovative drying methods was chosen to perform comparative study at different infrared power levels at 50, 62, 74 and 88 W. Quality attributes such as protein, fat, ash, carbohydrate, vitamin C content, solubility index and colour of infrared dried bee pollen samples were evaluated. The infrared power has a significant effect on the drying and quality characteristics especially colour. Drying time was reduced from 170 to 50 min when the infrared power level increased from 50 W to 88 W. Morphological changes on the surface of bee pollen grains increased with increasing the infrared power. The bee pollen infrared dried at 50 W retained its quality characteristics better than the bee pollens infrared dried at other power levels.

Pollen morphology of selected species of tribes Ingeae and Mimoseae (Mimosoideae—Leguminosae) occurring in the Atlantic Forest of the state of Rio de Janeiro, Brazil

The present work investigates the pollen of 14 taxa of the subfamily Mimosoideae (Leguminosae) occurring in the Atlantic Forest of the state of Rio de Janeiro, Brazil. The objective was to characterize the pollen grains of representatives of the subfamily Mimosoideae and to offer the knowledge for the taxonomy. Pollen grains were acetolyzed, measured, described and illustrated using light microscopy. Surface and aperture detail of non-acetolyzed pollen grains were observed and electromicrographed using scanning electron microscopy. The data were statistically analyzed in accordance with sample size. Only polyads were observed in the tribe Ingeae (Abarema Pittier, Albizia Durazz., Calliandra Benth. and Inga Mill.), while two types of pollen units were found in the tribe Mimoseae; the bitetrad type (Mimosa bimucronata (DC) Kuntze, Mimosa elliptica Benth., Mimosa pellita Humb. & Bonpl. ex Willd., and Piptadenia trisperma (Vell.) Benth.); and the polyad type (Anadenanthera colubrina (Vell.) Brenan, Mimosa ceratonia L., and Piptadenia pterosperma (Benth.) Brenan.). Thus, it can be concluded that the present evaluation of palynological characters allowed the separation of majority of the species studied and that the genera of the subfamily are eurypalynous.