Morphological Features Of Pollen Grains Research Articles

Taxonomic significance of pollen morphology of selected taxa of Bassia, Sedobassia, Spirobassia and Neokochia (Chenopodiaceae/Amaranthaceae sensu APG IV)

ABSTRACT Based on molecular phylogenetic and morphological studies, new genera Sedobassia Freitag & G. Kadereit and Spirobassia Freitag & G. Kadereit were described in the tribe Camphorosmeae (Chenopodiaceae/Amaranthaceae sensu APG IV). Palynomorphological peculiarities are often used in taxonomy as additional diagnostic features. Pollen grains from 26 herbarium specimens belonging to 13 taxa of Bassia, Sedobassia, Spirobassia and Neokochia genera in Eurasia and North America were acetolyzed and studied using both light microscopy and scanning electron microscopy. Dry pollen grains were also studied. The structure of columellae of pollen grains was analyzed for the first time in the current study. The aim of this research was to provide data on their pollen characteristics and to evaluate the taxonomic value of these data for generic and species-specific identification. Pollen grains are pantoporate, spheroidal in shape, circular in outline, slightly undulate, undulate or straight on the edges; medium or small-sized. Pores are circular, with distinct or indistinct margins. Exine sculpture is nanoechinate; tectum psilate or psilate-perforate. Pore membranes with nanoechini. Taxonomic relevance of the most important characters of pollen grains is discussed (pollen diameter, pore number, pore diameter, distance between pores and between pore centers, C/D value, nanoechini density, presenсe/absence of perforations, structure of columellae, number of nanoechini on pore membranes). Pollen morphology proved to be an important additional source of information for species-specific identification. This study provides new data and analyzes the morphological features of pollen grains of Bassia (in the currently accepted circumscription), palynomorphological similarities, and differences between the taxa of Bassia, Sedobassia, Spirobassia, and Neokochia genera.

The effect of herbicides on morphological features of pollen grains in Prunus serotina Ehrh. in the context of elimination of this invasive species from European forests

Prunus serotina Ehrh. is an alien invasive neophyte widespread in European forests. So far, no effective methods of its elimination have been developed. For this reason, the aim of our study was to determine how herbicides affect the morphological characteristics of pollen grains. This knowledge may be crucial to control this invasive species. The current study was carried out in a research area of 2.7 ha located in the Zielonka Forest near Poznań, Poland (N 52°31′58.016″, E 17°05′55.588″). We tested morphological differences among ten features of P. serotina pollen, based on the samples collected from 15 control trees compared to the 50 trees treated with five different herbicides. In total 1950 pollen grains were measured. We confirmed the adopted hypotheses of long-term herbicide influence on P. serotina pollen. Pollen grains from the control trees had a longer equatorial axis, were more elongated in shape and had the largest range of exine thickness compared to the pollen from the herbicide-treated samples. Exine thickness in the control sample was on average 0.74 µm, ranging from 0.42 to 1.19 µm. The average values and the ranges of this trait in the samples treated with herbicides were larger (e.g. average exine thickness was from 0.90 to 0.95 µm). There were differences in the P/E ranges of variability between the control and herbicide-treated samples. In the control sample the P/E ratio was 1.32–2.04 and elongated forms of pollen shapes prevailed, while in the herbicide-treated samples it ranged from 1.03 to 1.47. The share of deformed pollen grains in the herbicide-treated samples was lower than expected, ranging from 8.7 to 25.3%, while in the control samples it was 6%. Logo and Mustang turned out to be the most effective among the herbicides used in the described research. The two used application methods were found to have an effect on pollen quality.

Pollen morphological study and temperature effect on the pollen germination of cashew (Anacardium occidentale L.) varieties

Temperature is one of the main environmental factors that affects plant growth and development. Flowering phenology mainly pollination is highly sensitive to temperature extremes. Thus, pollen tests can be used as a tool to screen temperature tolerant crops. In present study, the in vitro pollen germination method was used for screening cashew varieties at different temperatures. The pollens of five cashew varieties comprising three early (VRI-3, Vengurla-4 and Ullal-3), one mid (Bhaskara) and one late (Madakkathara-2) were screened in field (in vivo) as well as at controlled temperatures from 5 to 50°C. The morphological features of pollen grains were also studied using Scanning Electron Microscopy (SEM). Significant differences in polar axis (P), equatorial axis (E) and P/E ratio were observed among five cashew varieties. Early varieties had high P and E. Pollen germination under in vivo was high for early types with optimum temperature (Topt) of 25°C while it was low in mid and late types with Topt of 30°C. The in vitro study further confirmed this finding, pollen germination at 25°C was 75% in early types while it was 57.8 and 50.5% for mid and late types respectively at 30°C. However, mid and late varieties exhibited better tolerance to high temperature beyond 40°C suggesting their wider adaptability to high temperature. The high reducing sugars mainly glucose and fructose in pollens of early varieties may be correlated to high pollen germination in response to temperature. Overall, the varietal differences in pollen behaviour can be used to select cashew varieties for evaluating their adaptability to temperature extremes during flowering across various regions.

Palynomorphological diversity among the Asteraceous honeybee flora: An aid to the correct taxonomic identification using multiple microscopic techniques.

This study aimed to characterize the palynological morphology of melliferous species of family Asteraceae belonged to seven tribes which were categorized into 15 genera and were studied under light and scanning electron microscopy. The pollen grains were acetolyzed, measured, and described qualitatively. Quantitative data were analyzed by descriptive and multivariate statistical analysis. The species were analyzed considering 11 quantitative pollen characteristics. The study revealed that the pollen grains are circular, triangular, angular, semi-angular, quadrangular, pentagonal and hexagonal amb, and 3-colporate or 3-colpate. The size of the pollen is variable among the species, ranged from 56.1 to 23.2μm. Three pollen types: oblate spheroidal (eight species), prolate spheroidal (six species), and suboblate (two species) were observed. The surface pattern of the exine varies from echinoperforate, echinate, echinate microperforate, fenestrate, echinoperforate reticulate, microreticulate, echinate perforate, tectate, and scabrate. Exine thickness was calculated minimum in Cichorium intybus (2.47 μm) and maximum in Taraxacum campylodes (5.15 μm). A key to studied bee floral species, based on the morphological features of pollen grains, is also provided. The palynomorphological characters here analyzed can be potentially used to correctly identify the Asteraceous honeybee floral species most commonly plants visited by honeybees in the study area.

Исследование влияния пыльцевых зерен на цвет меда из цветков Melilotus officinalis (L.) Pall.

Introduction. According to the Federal State Statistics Service, the Siberian Federal district produced 8,464.06 tons of natural polyand monofloral honey in 2019. The share of the Altai region was 45.37%, Krasnoyarsk region – 7.8%, regions, Omsk – 7.0%, and Novosibirsk – 6.3%. The color of honey is one of the main identifying characteristics of products. It largely depends on the chemical composition of pollen grains of honey plants. Therefore, it is relevant to study the color of honey from the nectar of Melilotus officinalis (L.) Pall.
 Study objects and methods. The research featured honey samples produced from the nectar of Melilotus officinalis (L.) flowers. The honey was centrifuged and pumped in 2018 on the territory of the Altai region. The research involved standard methods, as well as an authentic method for determining the dominant pollen grains. The method was based on preserving the morphological features of pollen grains and did not change their spatial location, thus making it possible to determine their real content in honey.
 Results and discussion. The honey color was affected by pollen grains of honey-bearing plants: 1) Melilotus officinalis (L.) Pall. (84.89%) > Fagopyrum tataricum (L.) Gaertn. (1.0%) > Convolvulus arvensis L. (0.97%) > Origanum vulgare (L.) (0.97%) > Brassicaceae Burnett, nom. cons. (11.20%); 2) Melilotus officinalis (L.) Pall. (49.24%) > Dracocephalum nutans L. (7.58%) > Trifolium pratense L. (9.09%) > Brassicaceae Burnett, nom. cons. (18.18%) > Sonchus arvensis L. (2.07%); 3) Melilotus officinalis (L.) Pall. (54.05%) > Helianthus annuus L. (14.87%) > Linaria vulgaris Mill. (2.70%) > Arctium tomentosum Mill. (4.05%) > Trifolium repens L. (8.47%) > Brassicaceae Burnett, nom. cons. (10.81%). Color and nutritional value depended mostly on two factors. The first factor was represented by flavonoid compounds (leucoanthocyanins, catechins, flavonols, etc.) of pollen grains of Melilotus officinalis (L.) Pall., Brassicaceae Burnett, nom. cons., and Helianthus annuus L. Their contents were 5.2, 3.1, and 2.8%, respectively. The other factor involved carotenoids – Trifolium pratense L., Trifolium repens L. and Origanum vulgare (L.). Their contents were 50.0, 37.3, and 28.7 mg/kg, respectively.
 Conclusion. The research featured honey from the flowers of Melilotus officinalis (L.) Pall. obtained from the South of the Siberian Federal District. Its color proved to be one of the main sensory properties necessary for establishing the botanical profile of the plants. The color depended on the secondary pollen grains of honey plants, containing flavonoid compounds and carotenoids.

Analysis of pollen morphological characteristics in Iranian Onobrychis Miller (Fabaceae) taxa

We verified the taxonomic importance of pollen grain characteristics, based on pollen morphology of 44 populations of 36 Onobrychis Miller taxa belonging to two subgenera and six sections, chiefly for delimitation of taxa, sections, and subgenera. We evaluated 1100 pollen grains (25 per taxon) and tested them by 13 qualitative and quantitative characteristics using scanning electron microscopy and light microscopy. For 19 Onobrychis species, pollen descriptions are presented for the first time. We used Image Tools, MVSP, and SPSS software for statistical analyses. Pollen grains of all the taxa were tricolpate, single, radially symmetrical, and isopolar. We identified three shape classes according to the polar/equatorial axes length ratio: prolate (the dominant), perprolate, and subprolate. The outline shapes in polar view were almost identical, while the taxa were different in the equatorial view of pollen grains. We found the following three exine sculpture types occurred in the species studied: reticulate, suprareticulate, and microreticulate. Our results suggest that Onobrychis pollen morphological characters were relatively homogeneous, which agreed with previous investigations. Nevertheless, our analyses revealed significant variation in pollen characters among the studied taxa, whereas the outputs of principal components analysis and hierarchical clustering vaguely confirmed the arrangement of the Onobrychis species into subgenera and sections according to Flora Iranica. Therefore, the morphological features of pollen grains in Onobrychis taxa have limited taxonomic importance for delimitation of subgenera, sections and species.

Systematic importance of morphological features of pollen grains of species from Erica (Ericaceae) genus.

The Erica genus has as yet not been investigated satisfactorily in terms of palynology. Its complicated taxonomic system, large number of species, as well as its extensive but disrupted range of occurrence, all contribute to the fact that few researchers have undertaken investigations of this species. It was assumed that the research results would be representative thanks to a complex comparative analysis of all diagnostical, morphological pollen features performed on properly selected plant material, representing the most important distinguished intrageneric taxons at the present time (45 species from all five subgenera and 22 sections), both discriminated pollen dispersal units (tetrads and monads) as well as the main centres of genus occurrence and diversification (species from Europe, the Republic of South Africa (RSA) and Madagascar). The study revealed that the diagnostic features of the pollen grains studied were: pollen dispersal unit, exine ornamentation, P/E ratio, tetrad diameter (D) and length of polar axis (P). On the basis of these traits, 14 Erica species (six creating monads and eight—tetrads) were distinguished which, in the case of pollen features, constitutes a significant number. Other heaths created small groups, usually containing two or three species, but up to seven species. The present study, based on the highest number of Erica species (45) analysed so far, corroborated the view that an examination of palynological features may assist in clarifying classification systems for the large and taxonomically very difficult Erica genus, in particular, at the level of the subgenus and section, but also at species level. The results obtained indicate the need to continue palynological investigations on the Erica genus.

Three-dimensional label-free imaging and analysis of Pinus pollen grains using optical diffraction tomography

The structure of pollen grains is related to the reproductive function of the plants. Here, three-dimensional (3D) refractive index maps were obtained for individual conifer pollen grains using optical diffraction tomography (ODT). The 3D morphological features of pollen grains from pine trees were investigated using measured refractive index maps, in which distinct substructures were clearly distinguished and analyzed. Morphological and physiochemical parameters of the pollen grains were quantified from the obtained refractive index (RI) maps and used to quantitatively study the interspecific differences of pollen grains from different strains. Our results demonstrate that ODT can assess the structure of pollen grains. This label-free and rapid 3D imaging approach may provide a new platform for understanding the physiology of pollen grains.

Selection of morphological features of pollen grains for chosen tree taxa.

ABSTRACTThe basis of aerobiological studies is to monitor airborne pollen concentrations and pollen season timing. This task is performed by appropriately trained staff and is difficult and time consuming. The goal of this research is to select morphological characteristics of grains that are the most discriminative for distinguishing between birch, hazel and alder taxa and are easy to determine automatically from microscope images. This selection is based on the split attributes of the J4.8 classification trees built for different subsets of features. Determining the discriminative features by this method, we provide specific rules for distinguishing between individual taxa, at the same time obtaining a high percentage of correct classification. The most discriminative among the 13 morphological characteristics studied are the following: number of pores, maximum axis, minimum axis, axes difference, maximum oncus width, and number of lateral pores. The classification result of the tree based on this subset is better than the one built on the whole feature set and it is almost 94%. Therefore, selection of attributes before tree building is recommended. The classification results for the features easiest to obtain from the image, i.e. maximum axis, minimum axis, axes difference, and number of lateral pores, are only 2.09 pp lower than those obtained for the complete set, but 3.23 pp lower than the results obtained for the selected most discriminating attributes only.

Pollen morphology of certain species of the family Lamiaceae in Saudi Arabia.

The intention of the present wok is to provide an account on the pollen morphological features of Lamiaceae in Saudi Arabia as a basis for future studies of Lamiaceae pollens in the region. Pollen morphology of 20 species belong to 16 genera of the Lamiaceae has been investigated using Light Microscope (LM) and Scanning Electron Microscope (SEM). The study revealed that the pollen grains were characterized by 3-zonocolpate or 6-zonocolpate. Size of the pollen is variable between the genera but not among the species of the same genus. The surface pattern of the exine varies from fine reticulate, rough reticulate, mega-reticulate, reticulate-perforate, bireticulate-perforate or granulate, leading to 6 types of pollen grains. These variations revealed by this study implies that pollen Morphology may be of significant value sharing in solving problems in the classification of Lamiaceae members. A Key to the species, based on the morphological features of pollen grains, is also provided.

Morphological Features of Pollen Grains in Portulaca

The morphological features of pollen grains collected from the broad-leaved and cylindrical-leaved Portulaca species of the Hawaiian Islands were investigated. The variation in size and surface pattern were examined using scanning electron microscopy and statistical analysis. Pollens of the Portulaca were apolar grains of monads exhibiting apertures, colpi, and relatively thin echini. Of particular interest was the differing size of pollen grains among the species studied. Pollens of the broad-leaved Portulaca were considerable in size with a length of about <TEX>$73{\sim}86{\mu}m$</TEX>, while the cylindrical-leaved Portulaca tended to have smaller pollen grains ranging from 50~65 in diameter. The smallest pollens were found in cultivar 2 having an average of <TEX>$43{\mu}m$</TEX>. The pollen was intectate, and the exine surface appeared granulous, having sculptured elements of spinules and puncta. Two types of puncta were discerned; one forming an operculum, and the other, a simple perforation. Numerous spinules and small puncta were found throughout the cylindrical-leaved Portulaca. In the present study, morphological features of pollen grains from ten Hawaiian Portulaca species, including endemic and unknown taxa, revealed the aforementioned pattern of variation. This paper aim to provide morphological information that could be of phylogenetic value within the Hawaiian Portulaca.

Comparison of pollen grain morphological features of selected species of the genusCrataegus(Rosaceae) and their spontaneous hybrids

The aim of our study was to verify, on the basis of statistical analyses of nine quantitative morphological features of pollen grains, the hypothesis that pollen grains of three parental species of Crataegus (C. laevigata, C. monogyna, C. rhipidophylla) differed from the pollen of three spontaneous hybrids of these species (C. × macrocarpa, C. × media, C. × subsphaericea). Contrast analysis revealed that a majority of the pollen features of hybrid species were characterized by significantly higher mean values than those of parental species. Analysis of pollen shape classes indicated that the parental species clearly differed from each other in contrast with hybrids, which were characterized by a similar proportion of pollen in individual pollen shape classes. Statistical analyses showed that the pollen grains of two parental species, C. laevigata and C. monogyna, were most similar to one another. Pollen grains of typical C. rhipidophylla were similar to the pollen of hybrids and the mean values of almost all studied pollen features [P, E, Exp, Exp/P, Le, d, d/E (PAI)] of C. rhipidophylla var. rhipidophylla were intermediate between those of C. monogyna and C. rhipidophylla var. lindmanii. This corroborates Zielinski's conjecture that C. rhipidophylla is probably an old, conserved hybrid between C. monogyna and C. calycina (= C. lindmanii = C. rhipidophylla var. lindmanii). According to the analysis of canonical variables, C. × macrocarpa and C. × media pollen grains were most similar. C. × subsphaericea and C. rhipidophylla var. rhipidophylla and C. rhipidophylla var. lindmanii formed another pair (group), and C. monogyna and C. laevigata constituted separate ‘single species groups’. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172, 555–571.

Palynomorphological features of Suaeda acuminata (C.A. Mey.) Moq., Suaeda prostrata Pall. and Tamarix ramosissima Ledeb.

The pollen morphology of Suaeda acuminata, S. prostratа and Tamarix ramosissima from Ukrainian flora has been studied with light and scanning electron microscopy. The main morphological features of pollen grains of three taxa, which spread within halophytes vegetation, are determined. The results has considered as potential useful for identification of the fossil pollen under paleopalynological or paleoecological study.

Pollen morphology of some Turkish &lt;i&gt;Campanula&lt;/i&gt; spp. and their taxonomic value

Detailed pollen morphological structures of 12 Turkish species of Campanula L., e.g. C. argaea, C. cymbalaria, C. glomerata subsp. hispida, C. latiloba subsp. latiloba, C. lyrata subsp. lyrata, C. olympica, C. persicifolia, C. pterocaula, C. rapunculoides subsp. cordifolia, C. rapunculus var. rapunculus, C. stricta var. stricta, C. pamphylica subsp. tokurii have been studied under light (LM) and scanning electron microscopes (SEM) for the first time. LM and SEM investigations show that the pollen grains of 12 taxa are more or less oblato-sphaeroidal, triporate (and/or tetraporate), tectum-scabrate, or with circular amb. The exine sculpture is granulate-scabrate in C. argaea, C. lyrata subsp. lyrata, C. stricta var. stricta, C. glomerata subsp. hispida and C. pamphylica subsp. tokurii; but those of C. cymbalaria, C. latiloba subsp. latiloba, C. olympica, C. persicifolia, C. pterocaula, C. rapunculoides subsp. cordifolia and C. rapunculus var. rapunculus are rugulate-scabrate.   Key words: Campanula, Pollen grains, Pollen morphology doi:10.3329/bjb.v37i1.1561 Bangladesh J. Bot. 37(1): 33-42, 2008 (June)

POLLEN STUDY IN RELATION TO BEE PASTURAGE

The importance of a full knowledge of bee pasturage is well known to the practical bee-keeper. Almost complete treatises about bee flora exist in all the chief honey producing countries. So far as South India is concerned, the industry is still in its infancy. Except for the records of Ramachandran (1937) and Venkatasubbayya (1938), no detailed informa- tion appears to be available and the present study was undertaken to supple- ment the information provided by them. But the attempt to ascertain plant sources for honey and pollen has in almost all studies reported in India, mainly been confined to the location of flowers actually visited by bees. This method cannot be deemed satis- factory, for it may be that plant sources growing at a long distance away from the apiary are missed. Also the worker's personal prejudices as to the usefulness or otherwise of a particular source may sometimes vitiate the reliability or completeness of the list of plants arrived at. The study of the external morphology of pollen grains has always formed a subject of absorbing interest to botanists. Pope (1925) and Wode- house (1928 and 1935) have studied the morphological features of pollen grains which are characteristic of the several families, the genera and the species of plants. From their observations, it seems possible that such characters as the size and shape of the pollen grains, the number and arrangement of germ pores and furrows, the character of reticulations and of spines, and the texture of the surface can be utilized in ascertaining bee pasturage. The present author is not aware of any work in which the pollen characters have been utilized for ascertaining bee pasturage in India. From the observations made on the pollen carried by the bees, the plants that are visited by them have been located and the seasons and the hours during which such visits are made have also been determined.