Large Pollen Grains Research Articles

Pollen Morphology in Relation to Taxonomy and Plant Geography of Resedaceae

Pollen morphological studies on 5 genera and 23 species have been made in the present investigation. Resedaceae is a stenopalynous family. Out of the three tribes, the tribe Cayluseeae is quite distinct pollen morphologically due to larger pollen size, apertural granules and exine ornamentation. The tribe Resedeae and Astrocarpae show close affinity. Reseda arabica Boiss. has larger pollen grains and stands apart in the tribe Resedeae. In this character it approaches the Caylusea sp. of the tribe Cayluseeae but in other pollen character they differ.The apertural granules in this family is interesting. Its nature, origin and significance will be useful.These apertural granules in this family suggest its closer relationship with the tribe Cleomae of the family Capparaceae from the palynological point of view.

Describing heterostyly, pollen, and sexual organ reciprocity in Rourea chrysomalla (Connaraceae), a rare and threatened species from the Brazilian Cerrado

Rourea chrysomalla is a rare and endemic plant species from the Brazilian Cerrado, presumably threatened and lacking records within conservation units. In this study, we recorded and characterized, for the first time, the floral and pollen dimorphism, as well as the reciprocity of sexual organs among different morphs of R. chrysomalla. For this purpose, fertile individuals were observed over three years in two natural populations and supplemented by herbarium data. This species is distylous and distinctly exhibits two types of flowers, each characterized by stamens arranged in two whorls of unequal lengths: L-styled and S-styled morphs, both occuring in similar proportions in the two populations. Cross-pollination among anthers of any stamen whorl in L-styled flowers and stigmas in S-styled flowers is more precise in the two morphs, while anthers in S-styled flowers are less reciprocal with the stigmas in L-styled flowers. S-styled flowers exhibit larger pollen grains compared to L-styled flowers, with no differences between the two whorls of stamens. The balanced proportion of floral morphs provides equal opportunities for pollen donation and reception, and reciprocity between morphs is essential for the conservation of R. chrysomalla due to its limited distribution and low population density in the central Brazilian savanna.

Species of the Western Palaearctic Genus Tetralonia Spinola, 1838 (Hymenoptera, Apidae) with Atypical Pollen Hosts, with a Key to the pollinosa-Group, Description of New Species, and Neotype Designation for Apis malvae Rossi, 1790

The long-horn bee genus Tetralonia consists of 35 Western Palaearctic species that are associated mostly with the family Asteraceae as host plants. A minority of the species are, however, exclusively associated with other host plants that have particularly large pollen grains, such as those in the plant families Caprifoliaceae, Malvaceae, and Onagraceae. This work presents a taxonomic account and morphological description of the assemblages of Tetralonia species with atypical (non-Asteraceae) host plants. It includes a key to the pollinosa-group, which contains most of the species, a description of three regionally restricted new species, namely T. eoacinctella Dorchin sp. nov., T. epilobii Dorchin sp. nov., and T. stellipilis Dorchin sp. nov., a lectotype designation for Eucera cinctella Saunders, 1908 [=Tetralonia cinctella (Saunders, 1908)], and a neotype designation for Apis malvae Rossi, 1790 [=Tetralonia malvae (Rossi, 1790)]. In addition, the name Eucera macroglossa Illiger, 1806 is confirmed as a synonym of Apis malvae Rossi, 1790; Tetralonia macroglossa ssp. xanthopyga Alfken, 1936 is officially placed in synonymy with Apis malvae Rossi, 1790; and Macrocera confusa Pérez, 1902 is listed as a doubtful synonym of Tetralonia scabiosae Mocsàry, 1879 (syn. nov.).

Relationship between pollination syndromes, pollen morphology and plant ecology in Quaternary deposits of the Cerrado

This study presents morphological descriptions and ecological information for 58 terrestrial pollen taxa and seven water-related pollen taxa from the Brazilian Cerrado, obtained from two sediment cores, Lake Feia (LFB1) and Getulio Swamp (VGE-17), encompassing the last 5000 and 15,000 cal yr BP, respectively. The relationships between the ecological and morphological traits (pollination syndrome, vegetation stratum and grain size) within each of the two depositional environments were investigated. In the LFB1 core, the pollen assemblages were dominated by arboreal pollen from closed physiognomies and lower storey trees (<10 m in height), while a combination of closed and open physiognomies was observed in the pollen assemblages from the VGE-17 core. The vast majority of the pollen taxa exhibited the entomophilous pollination syndrome, and a higher influx of entomophilous pollen was observed in both cores. Anemophilous and anemophilous/entomophilous syndromes were less well represented. Small and medium pollen grain classes were the most abundant, while the large pollen grain class was rare. The influx of small pollen grains was slightly more abundant in the lake record, while in the swamp record medium pollen grains were more abundant. Our results show that swamps and lakes differ in their representation of local versus regional pollen and in their sensitivity and responses to water-level changes. Landscape physiognomy also influences pollen dispersion: a closed physiognomy increases the local pollen signal, while a more open physiognomy results in better representation of local and regional signals.

Pollen morphology of Pinus sibirica (Pinaceae) mountain populations in the North-Eastern and South-Eastern regions of Altai

The influence of the climate humidity, mountain elevation and weather in the year of observations on the pollen morphology of the Siberian stone pine was studied. We compared the populations growing in the humid NorthEastern region of Altai (Mount Kolyushta, precipitation 867 mm/year, elevation 1350-1900 m) and the arid South-Eastern region of Altai (the Yuzhno-Chuysky ridge, precipitation 129 mm/year, elevation 1800-2100 m). It has been established that in an arid climate the body of a pollen grain is more spherical shape and larger in size, in a humid climate it is more ellipsoidal shape and smaller in size. It has been suggested that the tendency towards the formation of a spherical shape of the body of pollen grains is associated with the conditions of existence in an arid climate. Larger pollen grains were also formed in the lower mountain belts of both regions and in a year with warmer weather. Temperature has much less effect on the size of the air sacs, in contrast to the humidity of the region. In a humid climate, the sacs had an elongated shape, in an arid climate they were more rounded, but at the same time they did not differ significantly in volume. It is shown that the studied populations are more distant from each other in terms of the regional humidity factor, although the elevation and the weather also significantly influenced the pollen morphology of the Siberian stone pine.

Pollen-feeding behavior of diverse insects on Geranium delavayi, a flower with large, accessible pollen grains.

Why have pollen grains evolved to be exceptionally large in some species? Pollen-feeding hypothesis suggests that if the proportion of pollen amounts for feeding is reduced in a flower, the low allocation to pollen number would allow pollen grains to be larger. To examine whether species with large pollen grains experience low pollen consumption, the behavior of insects feeding on nectar and pollen was observed and pollen transfer efficiency was estimated for four visitor types in Geranium delavayi. To see whether bees actively collected pollen, the numbers of grains in pollen baskets and on the body were compared. Both nutritional value (total protein and lipid) and chemical defense (phenolic metabolites) in pollen against pollen feeders were measured. Bumblebees and honeybees foraged for nectar, rarely groomed pollen into corbiculae, and had >5× higher pollen transfer efficiency than smaller solitary bees and flies, which were pollen eaters that removed more pollen but deposited less. Pollen grains were characterized by low protein and high lipid content with a low protein-lipid ratio, an unfavorable combination for bumblebees. Three secondary metabolites were significantly higher in pollen grains (7.77 mg/g) than in petals (1.08 mg/g) or in nectar (0.44 mg/g), suggesting stronger chemical defense in pollen. Our results indicated that large bees took nectar but little of the nutritionally poor and highly toxic pollen. These data support one prediction of the pollen-feeding hypothesis, that species with few and large pollen grains would also have low pollen-consumption rates.

Acoustofluidic trapping device for high-NA multi-angle imaging

In the life sciences, there has been growing awareness that the traditional 2D cell culture model has its limitations in advancing our understanding of the mechanisms that underlie cell behavior, as the behavior and response of cells depend on the 3D microenvironment. Studying models such as suspended cell clusters and organoids is a step toward closing the gap between in vitro and in vivo studies. The fact that sample confinement and contact with surfaces have an impact on cells creates a need for contact-less tools for the inspection of live biological samples. Recently, we developed an acoustofluidic chip to trap and manipulate sub-millimeter-sized biological samples, and here, we demonstrate that this device can be adapted to support high-resolution imaging and illumination scanning for multi-view image acquisition. After coupling acoustic bulk waves into a microfluidic chip, the sample is levitated by an optically transparent transducer in the vertical direction. Two orthogonal side-transducers give additional control over the sample. By tuning the relative strengths of the three transducers and thus inducing an acoustic torque, we can transiently rotate the sample into various orientations for image acquisition. Under different operating conditions, exciting other modes, we can also induce sustained rotation of samples by means of other torque contributions and around axes perpendicular to the imaging axis, which is important to avoid “missing cone” artifacts in the tomographic reconstruction of the sample. We will discuss the modifications to our previously established device that were necessary to comply with the requirements for high-NA imaging and high-NA illumination. We provide a characterization of the performance and show examples of rotation and reorientation of biological samples, such as large pollen grains and cancer spheroids.

Cytology and pollen morphology of Bougainvillea glabra ‘Elizabeth Angus’, a cultivar with low pollen fertility

In this study, we analysed the pollen morphology, male gametophyte development, and callose deposition dynamics of Bougainvillea glabra ‘Elizabeth Angus’ to explore the period and mode of pollen abortion and the relationship between pollen morphology and fertility. Fertile pollen grains of ‘Elizabeth Angus’ and B. spectabilis ‘Pink Panther’ were larger than sterile pollen grains. Compared with the control ‘Pink Panther’, proportion of ‘Elizabeth Angus’ pollen grains with columellae was lower. Many abnormal phenomena were observed in pollen mother cells (PMCs) during meiosis, including laggard chromosomes, uneven chromosome separation, chromosome separation asynchrony, pentads, and micronuclei. At the early uninucleate stage, microspore development was abnormal, with deformed and shrunken pollen grains. Callose deposition was normal at meiosis and the tetrad stages of PMCs, but abnormal at the early mononuclear stage, with blocked microspore development. The complex abnormal chromosomal behaviour and delayed callose degradation in the early mononuclear stage during meiosis may account for the low pollen fertility of ‘Elizabeth Angus’. The size of the pollen grains and the morphology of the outer wall were associated with fertility; the larger pollen grains showed superior fertility, and the fertility of the pollen grains was associated with a certain number of columellae in the pollen wall. This study provides a theoretical basis for the genetic breeding of Bougainvillea.

Higher frequency of legitimate pollinators and fruit set of autotetraploid trees of Libidibia ferrea (Leguminosae) compared to diploids in a mixed tropical urban population.

In mixed-ploidy populations, newly formed polyploids initially occur at low frequencies when compared to diploids. However, polyploidy may lead to morphological and phenological changes, which promote reproductive isolation and favor polyploid establishment and reproductive success. Additionally, previous studies have shown that polyploidy can confer some adaptive advantages to organisms in stressful environments. Here, we investigate variation in reproductive phenology, floral traits and reproductive success between diploid and autotetraploid trees of Libidibia ferrea (Mart. Ex Tul.) L.P. Queiroz (Leguminosae) in a mixed tropical urban population, a stressful environment. We assessed ploidy levels, flowering and fruiting phenology, flowering synchrony, floral and reproductive biology, pollination and fruit and seed set. We tested the hypothesis that autotetraploid individuals have a higher frequency of pollinators and higher fruit and seed set per inflorescence (as a proxy of reproductive success) than diploids in an urban green space. Libidibia ferrea is a good model to test our hypothesis because it is self-incompatible (i.e. relies on pollinators to set fruits). In the urban ecosystem studied, we found that diploids flowered for 6-7 months/year and autotetraploids for 3-5 months/year. Flowering synchrony was low between and within cytotypes and even though autotetraploids and diploids exhibited some overlap in flowering period, diploids flowered alone for 2-3 months. Autotetraploids had significantly more flowers per inflorescences, larger flowers and larger pollen grains (as expected for polyploids), but also a higher frequency of visits by legitimate pollinators including two exclusive ones, and higher fruit and seed set per inflorescence when compared to diploids, despite having a shorter flowering period. Our findings reveal some advantages for polyploids over their related diploids in a tropical urban green space. Also, our results highlight the need for more studies that seek to understand abiotic mechanisms affecting reproductive output of polyploids in urban ecosystems.

Pollen typification and palynotaxonomy of subfamily Salsoloideae Ulbr. (Chenopodiaceae Vent.) in the flora of South Transcaucasia

The article presents the results of a comparative palyno-morphological analysis of the representatives of the Salsoloideae subfamily (Chenopodiaceae) in South Transcaucasia. Out of 25 species belonging to 13 genera of Salsoloideae subfamily in South Transcaucasia, pollen morphology of 23 species from 12 genera was investigated, as well as an analysis of the pollen characteristics was conducted. Data on five key features of pollen (on LM level) were statistically analyzed including pollen diameter, pore number, pore diameter, exine thickness, and mesoporium width. The results indicated that within the Salsoloideae subfamily of South Transcaucasian flora the first three features may be considered diagnostic. The application of a scanning electron microscope (SEM) has revealed the fourth diagnostic feature of the pollen within the Salsoloideae subfamily, specifically, the number of spinules on the unit surface of the pollen, which enables, in several cases, to conduct intergeneric or interspecific differentiation. Based on the obtained data, typification of pollen within the Salsoloideae subfamily of South Transcaucasia was carried out for the first time. As a result, two morphological types and four subtypes combined in two palynogroups were distinguished. The subdivision into palynogroups is based on differences in the size of pollen grains. Only species Climacoptera crassa with pollen of average sizes (26–33/29 μm in diameter) is included into the monotypic Palynogroup I, all other investigated species with small pollen grains (10–25 (27)/22 μm in diameter) are joined in Palynogroup II. Allocation of species into two different Types of Palynogroup II is based on the presence of a significant difference in the size of small pollen grains of individual species. In particular, species with relatively large pollen grains (&gt; 20 μm in diameter) are included in Type 1, while species with relatively small ones (≤ 20 μm in diameter) are joined in Type 2. And finally, the distribution of species into the subtypes and variations of Palynogroup II is based on differences in pore number and size. The identified key palyno-morphological features made it possible in some cases to specify the taxonomic boundaries, as well as the relationship between taxa within the subfamily Salsoloideae.

Comparative pollen morphology and its systematic implications in Resedaceae in Iran

The pollen morphology of Resedaceae in Iran has been studied using light and scanning electron microscopy and described in detail for the first time. Although most of the species had prolate or perprolate pollen grains, variation was observed in other diagnostic pollen characters. Based on exine ornamentation, the pollen grains could be divided into six main types: reticulate, macroreticulate, microreticulate, reticulate‐striate, rugulate and perforate, and eight subtypes. In addition, the studied species varied in pollen size, shape in equatorial and polar views, aperture features and ornamentation, representing Resedaceae as a eurypalynous family. The largest pollen grains belonged to Reseda lutea L., while R. aucheri subsp. rotundifolia (Kotschy ex Müll.Arg.) Rech.f. had the smallest ones. Furthermore, species of Ochradenus, Oligomeris and Reseda showed diagnostic palynological characteristics that may provide a better understanding of the taxonomy of Resedaceae. A dichotomous key based on pollen morphology to the 27 Resedaceae taxa native to Iran are also presented.

Managing Exacerbations in Thunderstorm Asthma: Current Insights.

Epidemic thunderstorm asthma (ETSA) occurs following a thunderstorm due to the interaction of environmental and immunologic factors. Whilst first reported in the 1980s, the world’s largest event in Melbourne, Australia, on November 21, 2016 has led to a wealth of clinical literature seeking to identify its mechanisms, susceptibility risk factors, and management approaches. Thunderstorm asthma (TA) typically presents during an aeroallergen season in individuals sensitized to perennial rye grass pollen (RGP) in Australia, or fungus in the United Kingdom, in combination with meteorological factors such as thunderstorms and lightning activity. It is now well recognized that large pollen grains, which usually lodge in the upper airway causing seasonal allergic rhinitis (SAR), are ruptured during these events, leading to sub-pollen particles respirable to the lower respiratory tract causing acute asthma. The identified risk factors of aeroallergen sensitization, specifically to RGP in Australians with a history of SAR, and individuals born in Australia of South-East Asian descent as a risk factor for TA has been key in selecting appropriate patients for preventative management. Moreover, severity-determining risk factors for ETSA-related asthma admission or mortality, including pre-existing asthma or prior hospitalization, poor inhaled corticosteroid adherence, and outdoor location at the time of the storm are important in identifying those who may require more aggressive treatment approaches. Basic treatments include optimizing asthma control and adherence to inhaled corticosteroid therapy, treatment of SAR, and education regarding TA to increase recognition of at-risk days. Precision treatment approaches may be more beneficial in select individuals, including the use of allergen immunotherapy and even biologic treatment to mitigate asthma severity. Finally, we discuss the importance of environmental health literacy in the context of concerns surrounding the increased frequency of ETSA due to climate change and its implications for the frequency and severity of future events.

Confirmation of distyly in Perovskia and floral dimorphism of P. abrotanoides (Salviinae: Lamiaceae)

Heterostyly is a specialised reproductive system with a reciprocal arrangement between the stamen and style, and often associated with tubular actinomorphic flowers. Accordingly, heterostyly is extremely rare in Lamiaceae, a representative zygomorphic flower group. However, some evidence indicates the occurrence of heterostyly in Perovskia. To confirm the existence of heterostyly, 288 herbarium specimens of Perovskia were observed, and a detailed floral morphological study was conducted on P. abrotanoides as a representative to diagnose the evolution of heterostyly. All examined specimens could be divided into two groups: a long-styled morph (L-morph) and a short-styled morph (S-morph), while P. abrotanoides, P. angustifolia, P. atriplicifolia, P. botschantzevii, and P. scrophulariifolia were recognized as distylous taxa. In P. abrotanoides, L-morph flowers possessed a larger calyx, a longer corolla, stigma, and anther, while significantly larger pollen grains and wider corolla were detected in S-morphs. Micromorphological structure and distribution patterns of trichomes were identical to both floral morphs, but the stomatal size on leaves and density of specific trichomes were somewhat different between morphs. Collectively, all data indicate a stable distylous condition of P. abrotanoides as the first case showing general heterostylous syndrome within Lamiaceae.

Pollen morphology and its taxonomic significance of the genus Crucianella L. (Rubiaceae) in Iran

AbstractThe Pollen morphology of nine species of Crucianella L. and ten subspecies of C. gilanica representing two sections: Roseae and Crucianella, was investigated using light microscopy (LM) and scanning electron microscopy (SEM). All the studied species (except for C. angustifolia) are palynologically described here for the first time. The results revealed considerable pollen character variation among the studied species. The pollen grains are monads, isopolar, radial symmetrical and relatively small. The largest pollen grains were observed in C. angustifolia (P = 24.12 µm, E = 26.04 µm), while the smallest pollen was found in C. gilanica subsp. carduchorum (P = 16.32 µm, E = 12.57 µm). The outline pollen grains varied from subcircular to circular in polar view and elliptical to quadrangular and circular in equatorial view. The shape of pollen changed from spheroidal to oblate‐spheroidal, prolate‐spheroidal, suboblate, subprolate and prolate. The pollen grains are zonocolpate and their number of colpi ranges from 6 to 10. The results showed five different types of sexine ornamentation: perforate, reticulate, microreticulate, microfoveolate and psilate. The sexine of all examined specimens is covered with microspines. The current survey shows that the pollen morphological characters of the studies species are taxonomically informative and may provide good help in identification purposes. We used multivariate analysis to determine the potential contribution of palynological data to the species relationships. The result of cluster analysis and principal component analysis showed pollen morphological affinities between the two studied sections.

&lt;p&gt;&lt;strong&gt;Palynological observations on the genus &lt;em&gt;Gundelia &lt;/em&gt;L. (Asteraceae) growing in Turkey&lt;/strong&gt;&lt;/p&gt;

The pollen morphology of 17 taxa of Gundelia, of which 13 taxa are endemic to Turkey, was investigated by light microscopy (LM) and scanning electron microscopy (SEM). In this study, the pollen morphology of 16 taxa except G. tournefortii was investigated for the first time. The quantitative data were analyzed by descriptive statistics and multivariate statistics. The pollen grains are oblate spheroidal and prolate spheroidal in shape with the polar diameter of 37.01–61.2 μm and the equatorial diameter of 31.2–63.4 μm. The smallest pollen grains were observed in G. anatolica, G. rosea and G. tournefortii, while the largest pollen grains were observed in G. vitekii, G. komagenensis and G. colemerikensis. Pollen ornamentation is echinate in LM and echinate-microperforate in SEM. Statistically, the relationships between pollen characters of the examined taxa were identified using Principal Component Analysis (PCA) and Clustering Analyzis. In addition, a dendrogram was constructed by applying UPGMA based on the determined 15 pollen morphological characters, and the degree of their relationship was discussed. Polar axis, equatorial diameter and colpus length were the major explanations of the pollen morphological characters’ total variation in PCA. Pair group method was used to divide the main pollen taxa into three groups based on the pollen morphology by using arithmetic averages analysis (PCA scatterplot and cluster analysis). As a result, the pollen shape, polar axis, equatorial diameter and spine length were important characters distingushing the taxa from each other. We found some matches and mismatches between pollen and morphological characters, whose significance requires further study.

A comparative study on morphological and fruit quality traits of diploid and polyploid carambola (Averrhoa carambola L.) genotypes

Artificially induced polyploid crops are generally associated with improved agronomic characteristics. Triploids and tetraploids previously created from the diploid carambola (Averrhoa carambola L.) cultivar 'B17′ (2n = 22) were used as experimental materials. The plody level of this new genetic material was checked by the combination of flow cytometry and by chromosome counting. The morphological characteristics and fruit quality of diploid and polyploid carambola were evaluated under field conditions. The results revealed that plants of different ploidy levels demonstrated significantly different phenotypic traits. Compared with their diploid counterparts, polyploids in general had greater vigor and biomass. Triploid and tetraploid plants produced stronger branches and petioles, more leaflets, thicker and larger leaves, larger pollen grains and flowers, bigger and heavier fruits as compared with that of diploid plants. However, a great decrease in the number of flowers was observed in polyploid plants, with 50 % reduction in the triploids as compared with the diploids. Furthermore, the majority of pollen from triploid plants was abnormal with collapsed structure and two different types of pollen grains were observed in the tetraploids using scanning electron microscope. Additionally, a general improvement in the quality of polyploid fruits was found when compared with diploid ones. In particular, the shelf life of polyploid fruits was much longer than their diploid counterparts. A comparative study was conducted among parental diploid carambola plants and their triploid and tetraploid deliverable offsprings based on morphological, physiological and agronomical traits. This study is expected to contribute into the breeding process for the production of new polyploid carambola varieties which will be characterized by special agronomical characteristics, better quality and longer self life period of their fruits.

Supergene evolution via stepwise duplications and neofunctionalization of a floral-organ identity gene

Heterostyly represents a fascinating adaptation to promote outbreeding in plants that evolved multiple times independently. While l-morph individuals form flowers with long styles, short anthers, and small pollen grains, S-morph individuals have flowers with short styles, long anthers, and large pollen grains. The difference between the morphs is controlled by an S-locus "supergene" consisting of several distinct genes that determine different traits of the syndrome and are held together, because recombination between them is suppressed. In Primula, the S locus is a roughly 300-kb hemizygous region containing five predicted genes. However, with one exception, their roles remain unclear, as does the evolutionary buildup of the S locus. Here we demonstrate that the MADS-box GLOBOSA2 (GLO2) gene at the S locus determines anther position. In Primula forbesii S-morph plants, GLO2 promotes growth by cell expansion in the fused tube of petals and stamen filaments beneath the anther insertion point; by contrast, neither pollen size nor male incompatibility is affected by GLO2 activity. The paralogue GLO1, from which GLO2 arose by duplication, has maintained the ancestral B-class function in specifying petal and stamen identity, indicating that GLO2 underwent neofunctionalization, likely at the level of the encoded protein. Genetic mapping and phylogenetic analysis indicate that the duplications giving rise to the style-length-determining gene CYP734A50 and to GLO2 occurred sequentially, with the CYP734A50 duplication likely the first. Together these results provide the most detailed insight into the assembly of a plant supergene yet and have important implications for the evolution of heterostyly.

Pollen grain size associated with pollinator feeding strategy.

Angiosperm pollen grain diameter varies greatly from a few microns to over 100, but the selective forces driving the interspecific variation in pollen size remain unclear. Although both pre- and post-pollination hypotheses have been proposed, empirical evidence remains scarce. Here we propose that visits by pollen-foraging pollinators have selected against large pollen grains. An association between pollinator behaviour and pollen grain size was confirmed by field studies of 80 flowering species in natural communities, showing that pollinators positively collected pollen in those species with relatively smaller pollen grains but rarely did so in species with larger ones. Allowing for the confounding effects of pollinator type, flower size or style length and pollen grain number, we found a significant effect of pollen-foraging behaviour on variation in pollen grain size, particularly in bee-pollinated plants. While these results suggest that many plant species whose pollen is collected or consumed by pollinators produce small pollen grains, it remains unclear whether pollen grain size is directly affected by pollinator foraging habit or indirectly mediated by pollen number trade-offs.

Buckwheat heteromorphic self-incompatibility: genetics, genomics and application to breeding.

Common buckwheat (Fagopyrum esculentum Moench 2n = 2x = 16) is an outcrossing crop with heteromorphic self-incompatibility due to its distylous flowers, called pin and thrum. In pin plants, a long style is combined with short stamens and small pollen grains; in thrum plants, a short style is combined with long stamens and large pollen grains. Both the intra-morph self-incompatibility and flower morphology are controlled by a single genetic locus named the S locus; thrum plants are heterozygous (Ss) and pin plants are homozygous recessive (ss) at this locus. Self-incompatibility is an obstacle for establishing pure lines and fixation of agronomically useful genes. Elucidation of the molecular mechanism of heterostylous self-incompatibility of common buckwheat has continued for a quarter of a century. Recent advances in genomic and transcriptomic analyses using next-generation sequencing have made it possible to determine the genomic region harboring the buckwheat S locus and to identify novel genes at this locus. In this review, we summarize the current knowledge on buckwheat heterostyly gained from conventional and molecular genetics and genomics. We also discuss the application of these studies to breeding of common buckwheat.

Morphological, anatomical, physiological, and cytological studies in diploid and tetraploid plants of Ispaghul (Plantago ovata Forsk.)

Ispaghul (Plantago ovata Forsk.) as an important medicinal plant has obtained a remarkable reputation due to therapeutic applications of seed mucilage. To determine the effect of in vitro-induced polyploidy on various characteristics of P. ovata, the terminal bud of two true leaves seedlings were separately treated with colchicine [0.1, 0.3 and 0.5% (w/v) for 6, 12 and 24 h] and trifluralin [7.5, 15 and 22.5% (w/v) for 24, 48 and 72 h] solutions. The ploidy level of induced tetraploids was determined via chromosome counting of root tip cells, and then confirmed through flow-cytometric analysis. Comparison the morphological, physiological, anatomical features of intact diploids and induced tetraploids revealed that tetraploids had considerable more height, thicker leaf, larger spike and seed, larger pollen grain and more seeds per spike. Moreover, the amount of chlorophyll (a, b, and total) and carotenoids, as well as chloroplast number in guard cells was further in tetraploids than diploids. Unlike density, stomata size in tetraploids was bigger than that one in diploids. It was also observed that seeds of tetraploids had more mucilage than diploids. In summary, we firstly developed the P. ovata tetraploids and suggested 0.3% colchicine for 24 h and 22.5% trifluralin for 72 h as the optimum treatments for inducing tetraploidy in P. ovata.