Pollen Surface Research Articles

Pollen morphology of eight tribes of Asteraceae from Universitas Indonesia Campus, Depok, Indonesia

Salamah A, Luthfikasari R, Dwiranti A. 2019. Pollen morphology of eight tribes of Asteraceae from Universitas Indonesia Campus, Depok, Indonesia. Biodiversitas 20: 152-159. Asteraceae is one of the largest flowering plant families in the world consisting of a high diversity of species that possess many macro-morphological characters. Ecological pressures have resulted in this highly varied morphology. Our research aims to describe the pollen morphology of the Asteraceae for species occurring in Depok Campus of Universitas Indonesia. Pollens of 14 species from eight tribes were extracted using acetolysis method and observed under a light microscope. The result showed that pollen unity, shape and pollen surface appeared to be differentiating characters of the Asteraceae from other families, while polarity and symmetry characters can be distinguishing characters at higher levels of the family such as subdivisions. Aperture characters were useful to differentiate between tribes. The shape of pores and size of pollen were not useful in differentiating between tribes, but may differentiate between lower taxa. The results of this study could be used as supporting data for regrouping taxa within the Asteraceae using morphological features.

Arabidopsis Protein Kinase D6PKL3 Is Involved in the Formation of Distinct Plasma Membrane Aperture Domains on the Pollen Surface.

Certain regions on the surfaces of developing pollen grains exhibit very limited deposition of pollen wall exine. These regions give rise to pollen apertures, which are highly diverse in their patterns and specific for individual species. Arabidopsis thaliana pollen develops three equidistant longitudinal apertures. The precision of aperture formation suggests that, to create them, pollen employs robust mechanisms that generate distinct cellular domains. To identify players involved in this mechanism, we screened natural Arabidopsis accessions and discovered one accession, Martuba, whose apertures form abnormally due to the disruption of the protein kinase D6PKL3. During pollen development, D6PKL3 accumulates at the three plasma membrane domains underlying future aperture sites. Both D6PKL3 localization and aperture formation require kinase activity. Proper D6PKL3 localization is also dependent on a polybasic motif for phosphoinositide interactions, and we identified two phosphoinositides that are specifically enriched at the future aperture sites. The other known aperture factor, INAPERTURATE POLLEN1, fails to aggregate at the aperture sites in d6pkl3 mutants, changes its localization when D6PKL3 is mislocalized, and, in turn, affects D6PKL3 localization. The discovery of aperture factors provides important insights into the mechanisms cells utilize to generate distinct membrane domains, develop cell polarity, and pattern their surfaces.

Pollen morphology of Quercus sect. Ilex and its relevance for fossil pollen identification in southwest China

Pollen grains of 16 modern species of Quercus were examined by scanning electron microscopy (SEM) and light microscopy (LM). The focus of this investigation was on a small group (c. eight species) of alpine, sclerophyllous oaks that may form a monophyletic group within sect. Ilex. The data were combined with published data for Polar axis (P) and Equatorial diameter (E) for more than 80 species. Based on pollen morphology Quercus pollen grains were divided into three types: (1) The Cyclobalanopsis type is smallest (generally < 23 μm) in size, with P/E ratios of approximately 1.08 and a psilate or fine-grained surface; (2) Quercus sect. Ilex type is 23–29 μm, the P/E ratio is approximately 1.24 (prolate) and it has a rugulate pollen surface; (3) the Quercus sect. Quercus type is generally > 29 μm in size, has a P/E ratio of approximately 1.04, and a clearly verrucate pollen surface. Based on a comparison with modern pollen size and ornamentation, fossil pollen grains of the Quaternary Qinghai Lake core can be assigned to the Chinese southwest mountain oak group of Quercus sect. Ilex (in particular Quercus semecarpifolia). In addition, we show that the pollen percentages of Quercus rapidly increased to the highest level during the glacial period. Using SEM for the identification of fossil Quercus pollen grains is essential to ensure the accuracy of differentiating evergreen Quercus types (sect. Ilex versus sect. Cyclobalanopsis) during the last glacial period in southwest China.

OsPKS1 is required for sexine layer formation, which shows functional conservation between rice and Arabidopsis

The sporopollenin precursors, as a general constituent of sexine, are synthesized in the tapetum and deposited on the pollen surface after transportation and processing. The polyketide synthase condenses the acyl-CoA into a hydroxyalkyl α-pyrone, which is predicted to be a component of the sporopollenin precursors. In this study, we found that the rice POLYKETIDE SYNTHASE 1 (OsPKS1) was the orthologue of Arabidopsis POLYKETIDE SYNTHASE A/LESS ADHESIVE POLLEN 6 (PKSA/LAP6) through sequence alignment. The OsPKS1 knockout mutants obtained by Crispr-Cas9-mediated editing exhibited a complete male sterile phenotype. Cytological observations revealed that abnormal bacula deposition and ubisch body structures for sexine formation led to pollen rupture in ospks1. The expression analysis showed that the OsPKS1 was highly expressed in tapetal cells and anther locules from stage 9 to stage 11 during anther development in rice. Subcellular localization demonstrated that the OsPKS1 protein was preferentially localized to the ER. The genomic sequence of OsPKS1 driven by the PKSA/LAP6 promoter restored the sexine pattern of Arabidopsis pksa/lap6. These results indicated that OsPKS1 is required for sexine layer formation in rice and functionally conserved in the sporopollenin synthesis pathway.

Physical and Biochemical Characterization of Chemically Treated Pollen Shells for Potential Use in Oral Delivery of Therapeutics

Allergen-free pollen shells obtained from natural pollen grains have recently attracted attention as microcapsules for oral therapeutic delivery. We have recently developed a chemical treatment method that enables successful retrieval of hollow pollen shells from diverse species. A comprehensive characterization is critical to characterize the effects of chemical treatment which will not only benchmark the pollen treatment process but can also lay the foundation of quality control procedures to check allergen-removal efficiency during pollen treatment. Therefore, in this study, we followed the effects of chemical treatment on 4 different pollen species using electron microscopy, elemental analysis, gel electrophoresis, confocal microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. These analyses revealed that acetone treatment removed lipids from the pollen surface. Phosphoric acid treatment removed proteins and nucleic acids from the pollen core and transformed esters into carboxylic acids. Potassium hydroxide hydrolysis changed carbohydrate composition of the pollen wall. Chemically treated pollen shells exhibited hydroxyl and carboxyl functional groups on their surface. Overall, we propose that confocal microscopy could be used as a rapid scanning technique to visualize the removal of biomolecules, whereas Fourier-transform infrared combined with gel electrophoresis could be used as a more objective approach for analysis and benchmarking.

Relationship between laser light scattering and physical properties of airborne pollen

Pollinosis (allergy to pollen) causes social and health problems around the world. Monitoring the actual amount of airborne pollen is essential to dealing with this problem. However, as measurements are usually done with the human eye using a microscope, enormous amounts of time and skilled labor are needed. We developed an automatic pollen monitor that uses laser optics to measure pollen more easily. With this method, unique ranges of light scattering intensities for each taxon of pollen, or “extract windows,” are searched and parameters for extracting subject pollen from observed data are clarified. These extract windows are determined using a scatter plot for the forward and side scattering intensities, based on the correlation coefficient between data from the automatic monitor and a Hirst-type sampler. In this paper, we present an analysis of data obtained by Le Réseau National de Surveillance Aérobiologique in Lyon, France in 2013 and by MétéoSuisse in Payerne, Switzerland in 2014 and 2015. Scattering intensities derived from the locations of extract windows for five pollen taxa were compared with physical properties of the pollen grains, clarifying that a positive relationship exists between the size of pollen and the intensity of forward scattering. We also investigated the ratio between side and forward scattering intensity and pollen surface characteristics using frequency analysis, finding a strong relationship between this ratio and the frequency spectrum of pollen surface structures. Larger roughness sizes on the pollen surface showed a clear relationship with the ratio between side and forward scattering intensity.

Uptake of ozone and modification of lipids in Betula Pendula pollen

Pollen allergy risk is modified by air pollutants, including ozone, but the chemical modifications induced on pollen grains are poorly understood. Pollen lipidic extract has been shown to act as an adjuvant to the allergenic reaction and therefore, the modification of lipids by air pollutants could have health implications. Birch pollen was exposed in vitro to ozone to explore the reactivity of O3 on its surface and on its lipidic fraction. Uptake coefficients of ozone were determined for ozone concentration of 117 ppb on the surface of native birch pollen (8.6 ± 0.8 × 10−6), defatted pollen (9.9 ± 0.9 × 10−6), and for crushed pollen grains (34±3 × 10−6). The mass of ozone uptaken was increased by a factor of four for crushed pollen compared to native pollen showing a higher susceptibility to ozone of cytoplasmic granules and broken pollen grains. A total mass of extractible lipids of 27 mg per gram of birch pollen was found and a fraction of these lipids was identified and quantified (fatty acids, alkanes, alkenes and aldehydes). The distribution of lipids was modified by ozone exposure of 115 and 1000 ppb for 16 h with the following reactivity: consumption of alkene, formation of aldehydes and formation of nonanoic acid and octadecanoic acid. The quantity of ozone trapped in the lipidic fraction during 15 min at 115 ppb is enough to contribute to the reactivity of one-third of the alkenes demonstrating that pollen could be susceptible to an atmospheric increase of ozone concentration even for a very short duration complicating the understanding of the link between pollen allergy and pollution.

Comparative morphological study of three species of Saraca L. (Fabaceae) by the statistical approach to find out the logic of potent morphological markers

The genus Saraca L. (Fabaceae s.l.) has 11 species among which three are distributed in India. This study is done for these three species as S. indica L., S. declinata (Jack) Miq., and S. thaipingensis Cantley ex Prain which are taxonomically recognized and identified by morphological characters, both of vegetative and reproductive. As a common trend of taxonomic study key to the identification of taxa is based on contrast pairs of lead characters considering as good characters to the taxonomic work when these characters are different in different taxa. The present study is emphasized here again to find out the marker characters for identity with the approach of preparation of ternary plot considering 82 characters through statistical method. Morphological characters like the texture of ovary, the presence of hood on anther and distribution of hairs on anther, bract and stigma morphology, shape and size of the seed, pollen surface etc. are found to be potent morphological markers for these three species of Saraca. The marker character to prepare a better key of identity is also established by this method. Earlier works on taxonomy also support this finding. The results show the relationship and character correlation amongst the species as S. declinata is more close to S. thaipingensis than S. indica. This work approaches a basis to strengthen a part of classical taxonomy.

Pollen fillers for reinforcing and strengthening of epoxy composites

Pollen grains have the potential to be effective plant-based biorenewable fillers in polymer matrices due to their high modulus, strength, chemical stability, and unique nanoscale architectures. In this work, we present evidence for the effectiveness of pollen as a reinforcing filler in epoxy matrices, characterized as a function of pollen loading and surface treatment. Composites prepared with unmodified native defatted ragweed pollen (D) displayed decreased mechanical properties and increasing glass transition temperatures (Tg) with increasing pollen loading. A soft interphase was observed to form around native pollen that is likely due to incompletely cured epoxy, resulting in decreased mechanical properties. However, pollen treated via a common base-acid (BA) surface preparation was a load-bearing, toughening filler in epoxy composites, displaying simultaneously increased tensile strength (by 47%) and strain at break (by 70%), improving interfacial morphology (absence of soft interphase), and increasing Tg at 10 wt% pollen loading. Elastic modulus improves by 14% with 10 wt% BA pollen loading, and fitting of the modulus with the Halpin-Tsai and Counto models results in an estimated pollen exine modulus of 8 GPa, the first reported pollen modulus measurement from composite studies. Improvements in mechanical properties in BA pollen versus D pollen likely result due to crosslinks with the epoxy matrix due to the presence of protic functional groups (hydroxyls or carboxyls) on the BA surface. BA-treated ragweed pollen shows promise as a toughening filler for imparting higher strength to polymers without increasing mass.

Morphological variation in pollen grains of Mucuna (Leguminosae): new biogeographic and evolutionary patterns

Mucuna comprises 105 species with an overall pantropical distribution and is divided into three subgenera: M. subg. Mucuna, M. subg. Stizolobium and M. subg. Macrocarpa. Although phylogenetic studies have supported the occurrence of three main clades, evolutionary relationships among them are not fully resolved. The objective of this study was to examine pollen grain morphology from representatives of all three subgenera and map these onto the phylogenetic trees generated by analysis of other characters. Pollen grain surface, form, size, and aperture number were compared. A Bayesian inference tree using matK sequences was constructed. The results indicate that the representatives of M. subg. Macrocarpa have the smallest pollen grains in the genus (a synapomorphic character here identified for this subgenus) and that species of subgenus Mucuna (those with umbelliform inflorescences) have the largest pollen grains. Additional morphological diversity of the pollen grain surface was noted: reticulate and/or micro-reticulate (in all three subgenera), perforate, gemmate or verrucose (only in M. subg. Mucuna). For all studied taxa, the pollen grains are triaperturate, except for two species of M. subg. Mucuna, which have tetraperturate pollen. The phylogenetic tree obtained using the matK marker resolved M. subg. Stizolobium as the earliest diverging lineage in Mucuna. Based on this phylogeny, a reticulate ornamentation pattern of the pollen surface may represent the ancestral state for the genus, while the larger pollen size and the foraminate, gemmate, and verrucose ornamentations are derived characteristics within the genus. These putative derived ornamentations have been observed only in neotropical species.

Ebenus zekiyeae (Fabaceae), a New Species from Turkey

Ebenus zekiyeae Aytac & Yildirim sp. nova (Fabaceae) is described and illustrated from Erzurum, eastern Anatolia, Turkey. It grows on dry, stony slopes and morphologically resembles E. reesei. Its diagnostic characters are discussed. The leaflet and pollen surface of E. zekiyeae were examined using scanning electron microscopy. Distributions of E. zekiyeae and E. reesei and an identification key to Turkish taxa of Ebenus are provided.

RESULTS OF SSR ANALYSIS, PROPERTIES OF PLANT MORPHOLOGY AND BIOCHEMICAL COMPOSITION OF CHINESE BROCCOLI – A NEW VEGETABLE CROP FOR RUSSIA

The results of estimation of growth and development parameters, SSR analysis, electron microscopic examination of the surface of pollen and seeds, biochemical composition (ascorbic acid, carotenoids, carotenes, macro- and microelements content in the stem part of plant) of 8 Chinese broccoli, Brassica oleracea var. alboglabra samples grown in the unheated greenhouse of the Central Siberian Botanical Garden SB RAS, Novosibirsk (54°49′33″ N, 83°06′34″ E) and phy- totron of N. I. Vavilov Institute of Plant Genetic Resources (VIR) have been presented. Through the study, the large surface cellularity of B.oleracea var. alboglabra (cv. “Siji Xianggu jie lan” [“SX”]) seeds was similar with seed coat surface of B.oleraceae var. capitata f. alba cv. "Slava". A scanning electron microscopic study of Chinese broccoli pollen (cv. “SX”) revealed the formation of colpate pollen with ellipsoidal shape with a size of 32.9 ± 0.76 x 17.8 ± 0.42 μm, characterized by foveolate ornamentation with a length-to-diameter ratio – 1.85.The duration of the period from emergence stage to thickening of a stalk and flower-bud formation of cv. “SX” continued for 49-54 days. Сlose correlation was established between the largest diameter of the stem and the length of the leaf petiole (r=0,87, p &lt; 0,001) and between the length of the leaf petiole and the weight of the stem (r=0,77, p &lt; 0,001). As a result of molecular screening of Chinese broccoli using 5 SSR markers (Na10D09, Ol12F02, Ra2E12, BC 7 и BC 65) the greatest polymorphism was in the test with the BC 7 marker - five alleles from 160 to 295 bp in size. In the “SX” variety single flowering (10%) occurred on 59 ... 63 day and mass flowering (75%) – on 65 ... 68 day. The stem part of B. oleracea var. alboglabra is a fairly good source of vitamin C, accumulating as much as 32-46 mg/100 g, and also increased concentration of K, Ca, Mg and Cu. At the end of the season the fruits, together with the phytomass of stems are well-seasoned for 3-4 weeks forming viable seeds with germination above 85% corresponding to the Russian state standard (GOST 32592-2013) for white cabbage seeds.

Pollen morphology of Chinese Sileneae and its systematic significance

ABSTRACTPollen morphology of 58 species and two subspecies of the genera Agrostemma, Cucubalus, Lychnis and Silene of Chinese Sileneae was studied using scanning electron microscopy. Among them, 50 species and one subspecies were reported for the first time. The results demonstrate that the number of pores and pollen surface ornamentation have important systematic significance. The surface ornamentation can be divided into four types, namely microechinate-perforate, microechinate-punctate, microechinate-reticulate and microechinate-punctate-perforate. The palynological characteristics support that (i) Cucubalus and Lychnis should be classified into Silene; (ii) Agrostemma and Silene are sister groups; and (iii) the infrageneric classification of Silene still needs further study.

Effect of aperture number on pollen germination, survival and reproductive success in Arabidopsis thaliana.

Pollen grains of flowering plants display a fascinating diversity of forms, including diverse patterns of apertures, the specialized areas on the pollen surface that commonly serve as the sites of pollen tube initiation and, therefore, might play a key role in reproduction. Although many aperture patterns exist in angiosperms, pollen with three apertures (triaperturate) constitutes the predominant pollen type found in eudicot species. The aim of this study was to explore whether having three apertures provides selective advantages over other aperture patterns in terms of pollen survival, germination and reproductive success, which could potentially explain the prevalence of triaperturate pollen among eudicots. The in vivo pollen germination, pollen tube growth, longevity and competitive ability to sire seeds were compared among pollen grains of Arabidopsis thaliana with different aperture numbers. For this, an arabidopsis pollen aperture series was used, which included the triaperturate wild type, as well as mutants without an aperture (inaperturate) and with more than three apertures. Aperture number appears to influence pollen grain performance. In most germination and longevity experiments, the triaperturate and inaperturate pollen grains performed better than pollen with higher aperture numbers. In mixed pollinations, in which triaperturate and inaperturate pollen were forced to compete with each other, the triaperturate pollen outperformed the inaperturate pollen. Triaperturate pollen grains might provide the best trade-off among various pollen performance traits, thus explaining the prevalence of this morphological trait in the eudicot clade.

Propolis in Livestock Nutrition

Our article provides the first demonstration about two theories concerning how it is produced. In his theory, Kustenmacher showed that in the summer, when plants profusely secrete oily balsamic substances on the surface of pollen, bees regurgitate them onto the comb and the walls of the hive, thereby producing propolis. Rosch showed that in late summer and autumn, bees collect resinous plant-derived substances and process them into propolis. As a substance of plant origin, propolis has a variable composition, depending on the plant species from which intermediates for its preparation are derived and the wealth of soil on which these plants grow. Propolis shows beneficial health effects, especially antibacterial, anti-inflammatory and anticancer activities, which make it a very important component of medication or supplement for human and animal healthcare. For this reason, propolis is one of the most widely used natural added to fodder. Since 1995, propolis has been recognized as a dietary supplement in Argentina.

Examination of pollen morphology of some Aethionema (Brassicaceae), from Turkey

Pollen morphology of 23 species of taxonomically difficult genus Aethionema W.T.Aiton was examined by light microscopy (LM) and scanning electron microscopy (SEM). Pollen grains have showed significant variation in aperture number and type. Generally pollen is tricolpate, but tricolpate-syncolpate, tetracolpate, or merely syncolpate apertures also occur and make a heteromorphic assemblage. Pollen shape is prolate, prolate-spheroidal, subprolate, spheroidal or suboblate, and pollen ranges from 9.4 to 29 µm (P), 6.2 to 23.9 µm (E). Five main pollen types were identified based on the sculpturing of the exine. The pollen shape, size, surface ornamentation, muri and lumina shape and size are found as important and useful features for distiguishing of the taxa

Pollen flora of Kastamonu university campus i: brassicaceae

Plants used in this study were collected from Kastamonu University campus and its surrounding in Turkey. Samples prepared according to Wodehouse (1935) technique, and they were examined by light microscopy to study the characteristic of pollen grains. Pollen grains of studied taxa observed as isopolar, radially symmetric with tricolpate aperture and prolate-spheroidal, subprolate and prolate pollen shape. Polar axis range between 15.30-43.53 µm while equatorial axis between 13.48-29.09 µm. Alyssum strigosum pollen measured as biggest pollen while Strigosella africana pollen is the smallest. Pollen surface ornamentation determined as reticulate. Exine thickness and intine thickness were varied between 0.4-2.3 µm, 0.1-0.9 µm, respectively. The characters like as polar axis, equatorial axis, pollen shape, pollen surface ornamentation, intine and exine thickness determined as important features for systematics of taxa

Sporogenesis, gametogenesis and pollen morphology of Solanum japonense and S. septemlobum (Solanaceae)

Solanum japonense Nakai and S. septemlobum Bunge are medicinal plants used chaotically in traditional Chinese medicine because they have the same Chinese name, Shuyangquan. In this study, anther wall development, microsporogenesis, male gametophyte development, megasporogenesis and female gametophyte development of S. japonense and S. septemlobum were studied using traditional paraffin section technology for the first time, and their pollen morphologies were compared using scanning electron microscopy. The results showed that both species exhibit dicotyledonous anther wall development, dual tapetum origination, secretory tapetum development, simultaneous microsporocyte cytokinesis, tetrahedral tetrad, coexistent 2-celled and 3-celled mature spheroidal pollen grains that are circular along the equatorial view and have tricolporate groves, 2 locules per ovary, axial placenta, anatropous, unitegmic and tenuinucellate ovule, linear megaspore tetrad, as well as monosporic Polygonum type of embryo sac, where the chalazal megaspore develops into the functional megaspore and the other three megaspores degenerate. However, the pollen grains of S. japonense are circular along the polar view, while those of S. septemlobum are triangular; the pollen surface ornamentation of S. japonense is granulate-verrucate-punctate, while that of S. septemlobum is granulate-punctate-fossula. These results enrich the embryological data of Solanum and provide palynological bases for the classification of these two species. https://doi.org/10.2298/ABS170724048L Received: July 24, 2017; Revised: October 20, 2017; Accepted: November 9, 2017; Published online: November 22, 2017 How to cite this article: Liu Y, Gu L, Liu J. Sporogenesis, gametogenesis and pollen morphology of Solanum japonense and S. septemlobum (Solanaceae). Arch Biol Sci. 2018;70(2):313-20.

Palynological features of eleven &lt;i&gt;Aethionema&lt;/i&gt; taxa from Turkey and their systematic implications

Pollen morphology of 11 taxa, including 2 endemic of the genus Aethionema W.T. Aiton from Turkey was examined under light and scanning electron microscopes. The pollens of Aethionema are mostly isopolar and bilaterally symmetric; spheroidal, prolate, perprolate and subprolate with the polar axes 14.07-26.41 μm and the equatorial axes 7.85-22.02 μm; mostly tricolpate, rarely 2-colpate; surface ornamentation is micro or macro reticulate. The exine thickness varies between 0.66 and 1.91 μm, and in tine thickness ranges from 0.27 to 0.85 μm. It is found that dimension of pollen grains, surface ornamentation, apocolpidium and amb diameter are taxonomically significant.Bangladesh J. Plant Taxon. 24(2): 197-204.

INP1 involvement in pollen aperture formation is evolutionarily conserved and may require species-specific partners.

Pollen wall exine is usually deposited non-uniformly on the pollen surface, with areas of low exine deposition corresponding to pollen apertures. Little is known about how apertures form, with the novel Arabidopsis INP1 (INAPERTURATE POLLEN1) protein currently being the only identified aperture factor. In developing pollen, INP1 localizes to three plasma membrane domains and underlies formation of three apertures. Although INP1 homologs are found across angiosperms, they lack strong sequence conservation. Thus, it has been unclear whether they also act as aperture factors and whether their sequence divergence contributes to interspecies differences in aperture patterns. To explore the functional conservation of INP1 homologs, we used mutant analysis in maize and tested whether homologs from several other species could function in Arabidopsis. Our data suggest that the INP1 involvement in aperture formation is evolutionarily conserved, despite the significant divergence of INP1 sequences and aperture patterns, but that additional species-specific factors are likely to be required to guide INP1 and to provide information for aperture patterning. To determine the regions in INP1 necessary for its localization and function, we used fragment fusions, domain swaps, and interspecific protein chimeras. We demonstrate that the central portion of the protein is particularly important for mediating the species-specific functionality.