Pollen Morphological Characters Research Articles

Pollen morphology of Artemisia L. (Asteraceae) in Turkey and its systematic value

The objective of the current investigation is to use scanning electron and light microscopy to obtain pollen morphological information for all Artemisia taxa growing in Turkey. In addition, statistical analyses were performed and a dichotomous key was prepared for the identification of taxa using pollen characters. Pollen grains of Artemisia are radially symmetrical, isopolar, oblate-spheroidal, and prolate-spheroidal, with the polar axis ranging from 15.23–27.20 µm. The equatorial diameter ranges from 16.48–27.47 µm. Artemisia taxa typically have tricolporate, tricolpate pollen. However, pantocolporate, pantocolpate, and syncolporate pollen grains are rarely present in A. austriaca and A. armeniaca. Our study showed that, although other Artemisia taxa have an ornamentation that is microechinate-granulate, A. incana, A. taurica var. vanensis, and A. spicigera differ by their microechinate ornamentation. Furthermore, we found that A. chamaemelifolia contains the highest number of microechinae per 25 µm2, whereas A. fragrans had the fewest. Additionally, the average number of granules differs between taxa. The number of granules per 25 µm2 is the highest in A. scoparia and the lowest in A. santonicum subsp. santonicum. Furthermore, the UPGMA (unweighted pair group method with arithmetic mean) dendrogram indicated that there are three different groups of taxa based on pollen morphological characteristics from 26 taxa. The average number of granules per 25 µm2, as determined by the principal component analysis, plays a significant role in this classification scheme.

The pattern of natural variability of palynomorphological features with the example of some <i>Nierembergia</i> and <i>Bouchetia</i> species (Solanaceae) and natural system of bio-variety

On the example of pollen morphological features of 8 species of Nierembergia and 2 species of Bouchetia (family Solanaceae), the properties of individual variability are described. Most of the studied characters (structure of apertures, ultrastructure of the sporoderm, surface sculpture, dimensions) do not have significant differences at the individual and intraspecific levels; taxonomically significant variability of morphological features of pollen is manifested at the level of the genus and suprageneric groups. The genera differ significantly in the sculpture of the pollen grain surface – striate in Nierembergia and tuberculate in Bouchetia. Pollen contained in one bud, anther or tetrad (fully completed gametophytic generation, where there is no death – all descendants of one ancestor without exception), is considered as an extreme model (maximum completeness with minimum complexity) to study the properties of natural morphological variability and the causes of its occurrence. It was found that pollen characters (sculpture, number and location of apertures) have the same pattern of variability (continuous and transitively ordered series), which embodied at different taxonomic levels in different characters. The natural variability of pollen morphological features is ordered not into a genealogical clade, but into a cline – continuous, geometrically ordered and transitive series (taxon-nonspecific and rank-independent). In this system of parallelisms, homological series are inseparable from non-homological ones, and typical forms, from deviations. The origin of typical and deviant forms cannot be explained separately (typical – genealogically, and deviant – as parallelism, convergence, chance or regularity). The individual variability of pollen forms is geometrically ordered and is not the result of random disturbances, failures of the hereditary program, or pathology. The typical form turns out to be a harmonious part of a geometrically ordered series of pure forms, free from functional and historical connotations. The similarity of pollen forms in these series is determined by their geometry and does not depend on affinity, homology, functionality (improvement, exercise, adaptation). The natural system of pollen forms is formed not by the structure of supposed affinity of supposed taxa (universalia, general concepts, the result of speculation that requires confirmation and admits refutation), but the structure of the observed parallelisms of the variability of individual living bodies. Evolutionary novelty (the current state, the observed variability) arises initially ordered in a pre-established form.

Pollen morphology of twenty three species of Allium L. (Amaryllidaceae) species from Turkey

The pollen morphology of 23 Allium L. species, grown in Turkey, belonging to the sections; Rhizirideum, Schoenoprasum, Cepa, Molium, Brevispatha, Scorodon, Acanthoprason and Melanocrommyum, were investigated by LM (light microscopy), TEM (transmission electron microscope), and SEM (scanning electron microscopy). This paper presents detailed pollen morphological features are given for these taxa. Common characteristics of pollen of Allium species investigated are ellipsoidal and heteropolar, bilateral symmetry; pollen grains are shed as monads. They are monosulcate (extended sulcate types) and monosulcate-operculate. The sculpturing of the exine, pollen membrane ornamentation, lumina shape, and sulcus membrane with a fragmented operculum are found to be characteristic features for separating species. Based on these properties three main pollen types were determined with three different exine sculpturing. The characteristic structures of pollen ornamentation, observed in SEM micrographs, are striate­perforate, striate­regulate-perforate and regulate-perforate. Sulcus membrane ornamentations are psilate, psilate-perforate, rugulate and regulate-perforate. The exine is semitectate and the tectum perforate. Columellae were found to be simplicolumellate. Bangladesh J. Plant Taxon. 30(1): 1-19, 2023 (June)

A taxonomic study on pollen morphology, karyotype features, floral and fruit pigment components of 13 taxa of Lonicera L.

Due to extensive introduction and breeding, the taxonomic relationships of Lonicera L. are unclear. Alternative scientific methods are needed to explore the classification of these new Lonicera. In this paper, the pollen morphology characteristics, karyotype features, and floral and fruit pigment components of 13 taxa of Lonicera were analyzed by means of scanning electron microscopy, karyotype analysis, High Performance Liquid Chromatography Mass Spectrometry (HPLC-MS) and Gas Chromatography-Mass Spectrometry (GC-MS). The 13 representatives of Lonicera were divided into groups of four, three, three and three taxa through the analysis of pollen morphology characteristics, karyotype features, floral composition and fruit pigment composition, respectively. Lonicera ruprechtiana and Lonicera tatarica always clustered together. Five hybrids, including Lonicera korolkow × Lonicera maackii and Lonicera korolkow × Lonicera tatarica No. 8 can generally be clustered with their parents. These results indicate that the analysis of pollen morphology characteristics, karyotype features, and floral and fruit pigment composition has value and significance for the study of systematic classification and relationships, and the conclusions of this study partially support morphological taxonomy.

Evaluation of grass pollen quality control for allergy test kit production using pollen morphological characters

Grass pollen is one of the leading causes of allergies in throughout the world. The symptom level depends on the personal immunity. Pollen allergy test kits are suitable for detecting allergic symptoms, which they are produced from pure pollen of specific species. The production of pollen allergy testing kits requires accurate botanical standards and identification for the process of quality control of raw materials basing on Thai Food and drug ministration (Thai FDA). To produce allergy test kit, we focused on the pollen of these 6 common grass species and also use pollen morphological characters for detection and identification. Therefore, this study focused on the method for qualification control and standardization for prototype product of grass pollen allergy testing kit. Six common grass species as Megathyrsus maximus (Jacq.) B.K.Simon & S.W.L. Jacobs, Oryza sativa L., Sorghum bicolor (L.) Moench, Urochloa eminii (Mez) Davidse, Urochloa mutica (Forssk.) T.Q.Nguyen and Zea mays L.). The criteria were: 1) common in Thailand and Southeast Asia; 2) high density in the atmosphere; and 3) severity of the allergic reaction. The modified acetolysis were applied for samples preparation. The pollen morphological (polar and equatorial axes, exine, porus, annulus and ornamentation) were observed and measurement under light and scanning electron microscope. The character matrix was analyzed based on a regression tree and Tukey’s HSD test to assess support for the different pollen morphological characters. The distinguished character is ornamentation. The results were successfully described the pollen species and showed that the pollen morphologies were useful for contaminated detection. In addition, this method was suitable applied for qualification control of the raw materials for grass pollen allergy testing kits production.

Pollen morphology of Scorzonera s.l. (Asteraceae, Cichorieae, Scorzonerinae) occurring in Iran

Pollen characters of 48 species of Scorzonera s.l. distributed in Iran were investigated by using light and scanning electron microscopy. The pollen grains are isopolar, radially symmetric, generally 3-zonocolporate, rarely 2-colpororate or 4-colporate. The pollen grains are oblate-spheroidal in shape (P/E=0.89 to 0.99) with the polar axes 37.1–58.1 µm and the equatorial axes 38.8–60.6 µm. We adopted the four pollen types recognized by Blackmore based on the number and position of their lacunae. For the first time, some pollen grains of S. longipapposa and S. tortuosissima were shown to have 26 (24+2) lacunae. We compared pollen morphological characters with the findings of the most recent systematic treatment. Type A with 6 lacunae was observed in Takhtajaniantha pusilla and S. parviflora, type B with 18 lacunae in Gelasia, type C with 20 lacunae in Pseudopodospermum and type D with 24 lacunae in Ramaliella, S. renzii and the Podospermum clade (except S. laciniata) in Scorzonera. We also observed 15 or 18 lacunae in S. rupicola. The pollen in Scorzonera appears to evolve toward reduction of spines in S. parviflora, extension of spines in the Podospermum clade, enlargement of the space between ridges and increase in the number of lacunae (S. longipapposa and S. tortuosissima). 26 pollen characters of the examined species were analysed by UPGMA and PCA. Pollen size, spine size, distance between spines, number and arrangement of spines between two equatorail lacunae, exine thickness, spine length/P or E, dimensions of lacunae and polar area were shown to contribute significantly to understanding the morphology of Scorzonera.

The morphological diversity of pollen in the genus Gossypium

BackgroundPlant pollen has diverse morphological characteristics that can be consistently passed down from generation to generation. Information on pollen morphology is thus immensely important for plant classification and identification. In the genus Gossypium, however, in-depth research on pollen morphology is lacking, with only few reports on limited cotton species. To evaluate the diversity of pollen in Gossypium, we therefore conducted a comprehensive analysis of the pollen morphology of 33 cotton species and varieties using scanning electron microscopy.ResultsThe 33 analyzed cotton samples exhibited common pollen morphological features, including spherical shapes, radial symmetry, echination, panporation, and operculation, while the pollen size, spine shape, spine density and length showed distinctive features. Pollen size varied significantly among species, with diameters ranging from 62.43 μm in G. harknessii to 103.41 μm in G. barbadense. The exine had an echinate sculptural texture, and spines were mostly conical or sharply conical but occasionally rod-like. Spine density varied from 173 in G. incanum to 54 in G. gossypioides, while spine length ranged from 3.53 μm in G. herbaceum to 9.47 μm in G. barbadense. In addition, the 33 cotton species and varieties were grouped at a genetic distance of 3.83 into three clusters. Cluster I comprised five allotetraploid AD-genome cotton species, four D-genome species, and one K-genome species. Cluster II included 13 diploid species from A, B, D, E, and G genomes, whereas Cluster III only consisted one E-genome species G. incanum.ConclusionsAlthough pollen characteristics alone are not enough to resolve taxonomic and systematic relationships within the genus Gossypium, our results add to knowledge on palynomorphology and contribute to phenological information on these taxa. Our findings should aid future systematic and phylogenetic studies of the Gossypium genus.

Heterostyly and pollen dimorphism of <i>Menyanthes trifoliata</i>

<i>Menyanthes trifoliata</i> L., a heterostyly plant, is an endangered species in Korea. Floral morphology has been published for <i>M. trifoliata</i>, but few works have concentrated on pollen dimorphism differences accompanied by floral dimorphism. Here, we conducted a comparative morphological study of two morphs to investigate a dimorphism system with Korean populations. Pollen morphological characteristics were observed with a light microscope and a scanning electron microscope. For the pin type, pollen size is 36.01 ± 2.01 µm, whereas for the thrum type it is 41.28 ± 2.58 µm in terms of the equatorial diameter. The two morphs have a small apocolpium field at 5.62 ± 0.30 for the pin type and 6.24 ± 0.70 for the thrum type. The configuration of the aperture was tricolpate with a striate ridge in the two morphs. However, they have different pollen shapes and sizes, stigma shapes, and apocolpium sizes. <i>M. trifoliata</i> only has different pollen sizes and shapes between European populations and Korean populations. Nevertheless, Korean populations also show pollen dimorphism correlated with their floral dimorphism.

The 3D Pollen Project: An open repository of three-dimensional data for outreach, education and research

Pollen is vitally important in the natural world, the scientific research which studies it, and society at large. Pollen is beautiful and immensely resilient, records millions of years of evolutionary, ecological and climatic change, underpins globally critical ecosystem functions and services, helps solve crimes, could revolutionise medicine – and, as one of humanity's most significant allergens, irritates hundreds of millions of people around the world.However, engaging non-specialists with pollen-related research can be challenging, because pollen's microscopic nature means all interactions with it must be visual, predominantly through static two-dimensional images (which obscure the grains' full 3D nature and beauty), complex stratigraphic diagrams (which can be impenetrable to non-specialists), or specialist microscopy (which adds complexity and expense). A recent development has been to use accurate and larger-than-life 3D-printed models, allowing audiences to interact with pollen and related research in new, tactile ways.This paper introduces the 3D Pollen Project, an open-access repository of 3D pollen scans and surface files. Confocal laser scanning microscopy was used to produce accurate series of tightly-focused cross-section images through pollen grains, which were reconstructed to produce 3D-printable surface files; both specific methods and underpinning general principles are outlined to enable others to emulate the work. Matching the refractive indices of sample mountant and objective lens immersion medium is shown to be particularly important for producing high-quality scans. The 35 species included in the 3D Pollen Project to date cover a broad (if Euro-centric) geographic distribution and a comprehensive suite of pollen's morphological features. These models, made available online for free download, have been used in a very wide range of contexts around the world, in outreach, education and research. Finally, future steps for the 3D Pollen Project are discussed: growing its coverage into a truly globally representative sample of global pollen diversity; enhancing the quality of its data; and developing the ways in which its resources are used.

Palynomorphological Observations on the Genus Sabulina Rchb. (Caryophyllaceae) from Turkey Using Light Microscopy and Scanning Electron Microscopy.

Pollen morphology of 28 taxa belonging to the genus Sabulina Rchb. (Caryophyllaceae) from Turkey was examined and compared using light microscopy and scanning electron microscopy. The current study aimed to describe the palynological characteristics of the Sabulina taxa and to assess the diagnostic value of these features for taxonomic implications. The pollen grains of Sabulina are radially symmetrical, apolar, rarely isopolar, and pantopolyporate with 8-28 pores. Their shape is prolate-spheroidal with the A axes (long axes) 19.5 μm and the B axes (short axes) 19-39.5 μm. Exine sculpturing is microechinate-punctate in all taxa. Principal component analysis was used to evaluate the significant pollen morphological characters for distinguishing the taxa, with three components accounting for 95.112% of the total variance. Numerical analysis revealed that pollen sizes, pore diameters, pore numbers, distance between pores, spinule density, and punctum numbers are particularly the most useful variables for separating the Sabulina taxa. The results also display a partial relationship between the Sabulina taxa clusters based on pollen morphology and the systematics of these taxa based on general macromorphology.

Assessment of Morphological, Anatomical and Palynological Variation in the Medicinal Plant Disporopsis longifolia Craib (Asparagaceae) for Botanical Quality Control

Disporopsis longifolia Craib is an Asian medicinal plant belonging to the Asparagaceae family. The plants are well known for their steroidal saponins and phenolic compounds and are traditionally used as tonics for back pain, bellyache, cough, diabetes, asthma, pneumonia and rheumatism. However, they are challenging to identify to species level using morphology. This raises a serious concern for their medicinal applications where botanical quality control is essential. The most appropriate morphological, anatomical and pollen characters for species diagnosis were therefore determined. Synonyms were identified and lectotypification provided. The morphological characters were described from 76 fresh and dried specimens to include a broad range of materials from differing habitats and locations. Paraffin and peeling methods were applied for anatomical studies of leaves and stems and a modified acetolysis method was undertaken for pollen morphology. This paper compares the new character data to published data from other species in the genus, namely D. aspersa, D. fuscopicta, D. jinfushanensis, D. pernyi and D. undulata. This is the first report of such anatomical and pollen morphology characters for D. longifolia. The results provide accurate morphological, anatomical and palynological characters for quality control and are best applied in combination with each other.

An insight into pollen morphology and evaluation of pollen viability, germination and mineral composition of some coconut (Cocos nucifera L.) genotypes

• Pollen morphology of eight coconut accessions differed in origin, stature, breeding behaviour and tolerance to abiotic stresses were characterised with scanning electron microscope. • Variations in pollen size, shape and exine ornamentation pattern was observed between the coconut genotypes. • Pollen physiological features such as pollen viability, germination and pollen tube length and pollen nutrient composition were evaluated for the eight coconut genotypes. • The results obtained revealed differences in pollen morphological features which can potentially be used for cultivar identification and the information on pollen viability, germination and pollen mineral contents amongst genotypes can support conservation and crop improvement studies of the genotypes. The micro-morphological characteristic of the pollen grain is one of the most important diagnostic traits use for identification and characterization of plants even to the accession levels. In this study, pollen grains characterization of eight different coconut ( Cocos nucifera L.) accessions were carried out. Morphometric observations and structure analysis of the pollen grains were performed using light and scanning electron microscopy. The variation in length and width observed ranged from 55.06 -71.25 µm and 24.38 -36.27 µm amongst the accessions. The pollen grains exhibited an ellipsoidal to elliptical shape with the exine ornamentation ranging from granulate to reticulate. Pollen viability, germination and pollen tube length were significantly different amongst the tested accessions. While pollen viability varied from 92.35 to 96.5%, germination rate and pollen tube length (after 2 h) ranged from 16.05 - 31.59% and 234.95 μm to 414.96 μm respectively. Pollen mineral composition from different accessions also varied significantly with Malayan Orange Dwarf (MOD) recording higher phosphorus (0.93%), calcium (0.64%) and magnesium (0.38%) content while highest potassium (1.01%), sodium (0.71%), iron (149.35 ppm) zinc (119.59 ppm) and boron (45.05 ppm) content was noticed in San Ramon Tall (SNRT). This investigation highlights the fact that these pollen morphological features could be potentially used for differentiating the selected accessions thereby supporting their conservation and crop improvement studies.

A New Pollen Aperture in Schleichera oleosa (Lour.) Oken from Madhya Pradesh, Central India, and its Taxonomic and Evolutionary Significance

Angiosperms demonstrate a surprisingly frequent phenomenon of variability in the gross pollen morphological characteristics. In thepresent study, we recorded and described a new aperture in the pollen grains of Schleichera oleosa (Lour.) Oken, a monotypic genusof the soapberry family Sapindaceae, from Madhya Pradesh, central India, based on the LM and CLSM observations. This condition istermed the tetra-zono-parasyncolporoidate condition. A new pollen aperture has been recorded in this monotypic genus with theusual one (tri-zono-parasyncolporoidate condition), and this phenomenon of the occurrence of a new with increased number of pollenaperture is known as pollen aperture heteromorphism. The study will further help identify this taxon from the sedimentary archives asone of the indicators of the warm and humid (moist) climate and increased monsoonal rainfall.

Pollen morphology of some selected species of the tribes Brassiceae, Conringieae, Isatideae, and Plagiolobeae (Brassicaceae) in Iran, and its taxonomic significance

ABSTRACT Pollen morphology of 12 species, representing tribes Brassiceae, Conringieae, Isatideae, and Plagiolobeae genera were studied using light microscopy (LM) and scanning electron microscopy (SEM). The results demonstrated that the polar diameter, pollen exine ornamentation, mesocolpium width, and exine thickness have important systematic significance. The results revealed that pollen grains in these genera were tricolpate and their shapes varied from prolate to perprolate, with the polar axis ranging from 30.28 to 41.05 µm and the equatorial axis from 17.21 to 23.36 µm. However fine details are characteristic of distinguishing pollen grains in the species of the genera. The exine ornamentation varied among genera within the tribes and species within the same genus. Three pollen types are distinguished based on lumen size. All the studied tribes’ pollen were heterogeneous with ornamentation reticulate, ornamentation microreticulate (Conringia orientalis, Plagioloba derakii), and ornamentation macroreticulate (Moricandia sinaica). The exine thickness ranged from 0.75 to 2.60 µm. Pollen characteristics support: (i) two distinct pollen types viz., Conringia austriaca and Iljinskaea planisiliqua types in all four tribes; (ii) the similarity of the pollen shape tribes Isatideae and Brassiceae; (iii) confirmation of the transfer of P. crenulata from Zuvanda to Plagioloba, and I. planisiliqua from Conringia to Iljinskaea, respectively. Plagioloba clavata have great variations in the pollen morphological characters in Plagioloba and needs to be further studied. The key to the species of the genera was also provided.

Pollen morphological characters variation among species of Strobilanthes s.l. from Sumatra, Indonesia and its taxonomic implications

Abstract. Suratman, Suranto, Muzzazinah, Purnomo. 2022. Pollen morphological characters variation among species of Strobilanthes s.l. from Sumatra, Indonesia and its taxonomic implications. Biodiversitas 23: 4636-4648. The objective of this study was to evaluate pollen morphological characters variation and its taxonomic value among species of Strobilanthes s.l. from Sumatra. A total of 32 species from four genera previously recognized within the subtribe Strobilanthineae were used for pollen morphology observations using Light Microscope (LM) and Scanning Electron Microscope (SEM). A total of ten pollen morphological characters (both quantitative and qualitative) were observed in this study. In general, a great variation occurs in the majority of investigated pollen morphological characters. A similarity dendrogram among species of Strobilanthes s.l. based on pollen morphological character data revealed two major clusters. Cluster I consist of 25 species that differed from species in Cluster II in having pollen type I, pollen type II and pollen type III with a similarity coefficient of 0.61. Cluster II consists of seven species and has pollen type IV, pollen type V, pollen type VI and pollen type VII with a similarity coefficient of 0.46. An identification key to the species of Strobilanthes s.l. based on pollen morphology is also established for easy discrimination of the investigated taxa. This study revealed that pollen morphology was taxonomically useful character for identification and taxa delimitation of Strobilanthes s.l., especially at the species level. The results of this study also support earlier works through molecular studies, statistical analysis, gross morphology observations and leaf anatomy studies that all segregate genera of the subtribe Strobilanthinae should be merged under a single and well-defined genus as Strobilanthes s.l.

Tricolporate pollen of caesalpiniaceae medicinal plants at Kotla Vijaya Bhaskara Reddy botanical garden in Cyberabad, Telangana

This paper presents the study of a tricolporate pollen morphology of 08 Caesalpiniaceae medicinal plant taxa viz. Bauhinia purpurea L., Caesalpinia pulcherrima( L.) SW.,Cassia fistula L., Delonix regia (Hook.) Raf., Peltophorum pterocarpum (DC.) K.Heyne., Senna auriculata L., S. sophera (L.), Roxb. and Tamarindus indica L. The flower buds of these plants were collected from blocked category of Cyberabad area i.e. Kotla Vijaya Bhaskara Reddy Botanical Garden. By using Erdtman’s (1960) acetolysis technique, the collected flower buds were processed. The result of the study showed that Caesalpiniaceae tricolporate pollen grains have diversity in their pollen morphological characters like Polarity, Symmetry, Shape, Aperture and Sporoderm. The observations of this study will be useful for authentic identification of the taxa of Caesalpiniaceae.

Palynological diversity of highly medicinal rare, endangered, and threatened plants from Western Himalaya, India

The present study investigated the palynological diversity of highly medicinal Rare, Endangered, and Threatened (RET) plant species dwelling in higher altitudes of Western Himalaya, India. The pollen morphology of 32 plant species covering 29 genera, 23 families, and 18 orders of Angiosperms was analyzed by Light Microscopy (LM) and Scanning Electron Microscopy (SEM). The families of the studied plant species have been arranged and discussed following the evolutionary sequence as per the updated version of Angiosperm Phylogeny Group ІV. The studied pollen characters were found to be helpful in the delimitation of taxa at the species level. In the studied monocots, the species belonging to order Zingiberales, Asparagales, and Liliales followed the general trend of having primitive inaperturate to advance monosulcate pollen except for Alismatales which had inaperturate pollen and placed after the orders mentioned above in the APG ІV classification system. The pollen aperture of the eudicot group in the present study followed the evolutionary pattern from tricolpate to tricolporate and triporate, which corroborated previous reports. All the investigated species of both monocot and eudicot groups had monad pollen units suggesting their primitiveness on the evolutionary scale except for the Rhododendron companulatum (Ericales), having evolutionarily advanced tetrad arrangement. The current study found primitive exine ornamentation in Ranunculales to advance in Asterales, Lamiales, Gentianales, and Boraginales and confirms the results of the previous studies. The data on the pollen morphological features of the studied species generated in the present study will help understand these important high-altitude plant species' reproductive biology and conservation aspects.

The effect of diagenesis and acetolysis on the preservation of morphology and ultrastructural features of pollen

Pollen morphology on its own and in conjunction with other characteristics has elucidated the origin and evolution of various plant groups. Previous studies of fossil pollen rarely discuss the effects of diagenesis and sample preparation on pollen characteristics, i.e., variability in staining, pollen morphology, and pollen wall ultrastructural characteristics. This paper examines the effect of acetolysis on reflectance and spectral epi-fluorescence measurements. Based on empirical studies, different species under similar experimental conditions display different reflectance values, indicating individual species respond differently to similar post-depositional thermal events. The quantitative pollen fluorescence spectra showed significant variability, but there is an overall increase in the mean wavelength of maximum emission with acetolysis. Increases in these spectral parameters are used to infer thermal maturation and diagenetic pathways in fossil pollen. The paper also discusses observations made on fossil pollen of a known thermal maturity using Pearson's Pollen/Spore Color Standard. Assessment of pollen thermal maturity using this color standard can be an indicator of the quality of morphological and ultrastructural information that can be extracted from fossil pollen. Increasing thermal maturity of pollen may have an effect on staining variability. Based on observations, staining for brightfield or electron microscopy in fossil pollen, although useful for improving contrast in the specimen, must be used with caution when interpreting pollen wall structure. Although single fossil pollen investigations are useful, replication of these studies on similar or the same specimens from the same locality or various localities will collectively provide more information for elucidation of the morphology and ultrastructure of the once living pollen, and is helpful in sorting out characteristics that may be artifacts from post-depositional diagenesis.

Pollen characters and their evolutionary and taxonomic significance: using light and confocal laser scanning microscope to study diverse plant pollen taxa from central India

Increasing the taxonomic resolution of fossil pollen identification and establishing the kinship and similarity among phylogenetically related plant groups are inevitable for advancing the Quaternary palaeoecological, palaeoclimatological and palaeoenvironmental research. We, in the present study, examined and determined the pollen morphological characteristics of nine plant taxa belonging to seven families from central India by a combined light microscopic (LM) and confocal laser scanning microscopic (CLSM) study. The prime object was to observe, document and describe, as well as illustrate the prevalent variation in pollen shape, size, aperture number and diameter, diameter of the polar axis and equatorial distance, as well as exine thickness and pattern (i.e. pollen wall architecture) of the studied plant taxa. Pollen identification key was developed to demonstrate variations in pollen features and delimit taxa for correct identification. Principal component analysis (PCA) suggests exine and aperture number as dominant characters, as well as hierarchical clustering analysis (HCA), applied to the pollen morphological characters of nine plant taxa to understand the variability among the taxa, and to cluster them, respectively, suggest three clusters. The cophenetic correlation coefficient also substantiates the three group of clustering. The present study has significance in taxonomy and systematics, as well as in phylogeny and evolution. In addition, the preservation potential of different pollen grains has been ascertained, based on the pollen wall architecture. The study, moreover, will improve the precise fossil pollen identification, which is critical for advancing Quaternary palaeoecology in India and also in similar tropical and subtropical areas of the globe.

Pollen of Pterocarya (Juglandaceae) representatives from natural habitats and St. Petersburg environments

Background. Comparative palynomorphological studies of naturally occurring and introduced Pterocarya Kunth representatives reveal the taxonomic significance of pollen morphological features and pollen characters of cultivated plants. The quality of pollen material and the potential of the plants from the Botanical Garden of BIN RAS for introduction are characterized.Materials and methods.Pollen grains were investigated using light, confocal laser scanning and scanning electron microscopes. Fertility was assessed using the standard acetocarmine method.Results.Comparison of pollen morphology in cultivated and naturally growing plants of this genus was made for the first time. Pollen fertility of two cultivated species (Pterocarya rhoifolia Siebold et Zucc., and P. stenoptera DC.) was very high, generally over 90%. Fertility of P. fraxinifolia (Lam.) Spach grains varied from 28 to 73% in different years, which is a low or medium level of pollen quality. Morphologically, pollen grains of all 12 specimens from five taxa are flattened, medium sized, 21–45 μm in diameter, with 4–8 pores; pores are located mainly at or near the equator. The pores are round or oval, with a limbus. Exine is three-layered, thickened near the pore. The sculpture is microechinate. The low-fertile P. fraxinifolia specimen contains small pollen grains, as well as grains in tetrads and dyads. The data on the introduction of the genus in St. Petersburg are presented.Conclusion.The palynonomophological description is diagnostic for the genus Pterocarya. The Pterocarya pollen is well distinguishable from other wind-pollinated taxa; however, species identification by pollen for spore-pollen analysis is not practicable. Morphologically, the most diverse are the grains of the low fertile specimen P. fraxinifolia. The limited possibility of seed propagation of P. fraxinifolia is probably explained by low pollen fertility. The pollen quality of the introduced P. rhoifolia and P. stenoptera is high.