Large Pollen Grains Research Articles

Cirsiumtatakaense (Compositae), a new species from Taiwan.

A new species of Cirsium, Cirsiumtatakaense Y.H.Tseng & C.Y.Chang, from central-southern Taiwan is described and illustrated. This species is similar to C.kawakamii Hayata in leaf shape, achene and chromosome number (2n = 64), but can be readily distinguished from C.kawakamii by the narrower leaf lobes, usually higher number of florets and phyllaries, the purplish-red corolla (vs. white) and larger pollen grains. A key to the species of Cirsium in Taiwan is also presented.

Polyploidy in Fruit Tree Crops of the Genus Annona (Annonaceae).

Genome duplication or polyploidy is one of the main factors of speciation in plants. It is especially frequent in hybrids and very valuable in many crops. The genus Annona belongs to the Annonaceae, a family that includes several fruit tree crops, such as cherimoya (Annona cherimola), sugar apple (Annona squamosa), their hybrid atemoya (A. cherimola × A. squamosa) or pawpaw (Asimina triloba). In this work, genome content was evaluated in several Annona species, A. triloba and atemoya. Surprisingly, while the hybrid atemoya has been reported as diploid, flow cytometry analysis of a progeny obtained from an interspecific cross between A. cherimola and A. squamosa showed an unusual ploidy variability that was also confirmed karyotype analysis. While the progeny from intraspecific crosses of A. cherimola showed polyploid genotypes that ranged from 2.5 to 33%, the hybrid atemoyas from the interspecific cross showed 35% of triploids from a total of 186 genotypes analyzed. With the aim of understanding the possible implications of the production of non-reduced gametes, pollen performance, pollen size and frequency distribution of pollen grains was quantified in the progeny of this cross and the parents. A large polymorphism in pollen grain size was found within the interspecific progeny with higher production of unreduced pollen in triploids (38%) than in diploids (29%). Moreover, using PCR amplification of selected microsatellite loci, while 13.7% of the pollen grains from the diploids showed two alleles, 41.28% of the grains from the triploids amplified two alleles and 5.63% showed up to three alleles. This suggests that the larger pollen grains could correspond to diploid and, in a lower frequency, to triploid pollen. Pollen performance was also affected with lower pollen germination in the hybrid triploids than in both diploid parents. The results confirm a higher percentage of polyploids in the interspecific cross, affecting pollen grain size and pollen performance. The occurrence of unreduced gametes in A. cherimola, A. squamosa and their interspecific progeny that may result in abnormalities of ploidy such as the triploids and tetraploids observed in this study, opens an interesting opportunity to study polyploidy in Annonaceae.

Palaeoenvironmental reconstructions during the Meso- to Neolithic transition (9.2–5.3 cal. ka BP) in Northwestern France: Palynological evidences

Sedimentological, palynological, and micropalaeontological studies carried out throughout the first half of the Holocene, during the Mesolithic/Neolithic transition in the Bay of Brest (i.e. 9200–9000 and 6600–5300 cal. BP) and in the Bay of Douarnenez (i.e. 9200–8400 cal. BP), allowed characterizing coastal environmental changes under the increasing influence of the relative sea-level rise. The gradual flooding of the two studied sites implied a transition from river valleys to oceanic bays as revealed by the gradual retreat of salt marsh environments, as detected through palynological analysis. In addition, these high-resolution studies highlight the regional imprint of the North Atlantic millennial climate variability in north-western coastal environments. Two cold climate events are indeed suggested to have been locally marked by a moisture increase, mainly detected by increases in Lingulodinium machaerophorum, Corylus, and Alnus percentages at 8550 cal. BP in the Bay of Douarnenez and at 6250 cal. BP in the Bay of Brest. Moreover, regarding the Neolithic transition timing in the Bay of Douarnenez, large pollen grains of Poaceae (i.e. Cerealia-type pollen grains) have been detected at around 8600 cal. BP, that is, 1500 years before the general accepted cereal cropping appearance in Western France. These results, consistent with other palynological studies conducted in the French Atlantic coast, could underline a Mesolithic ‘proto-agriculture’ in Brittany.

Reproductive diversity, polyploidy, and geographical parthenogenesis in two Eriotheca (Malvaceae) species from Brazilian Cerrado

Breeding systems have been associated with polyploidization and genomic change, which have a central role in the diversification of Angiosperms. Polyploidy commonly leads to isolated populations and species, and sometimes to apomixis, as observed for some woody plants of Cerrado, the Neotropical savannas in Central Brazil. Eriotheca gracilipes and E. pubescens are common trees in this region, and present both sexual and sporophytic apomictic individuals. We studied here how morphological features and breeding systems are linked to ploidy and genome size differences, and how these features may help to understand cytotypes distribution. We confirmed breeding systems by hand pollination experiments and complemented histological analyses to describe the apomixis and sexual process for individuals with previously defined ploidy levels. We used flow cytometry and morphometry data to verify the relationships among cytotypes. Fruit and seed features were also measured for extensive samples of both species to observe environmental correlates such as altitude of occurrence and distribution of each embryony pattern and cytotypes. In both species, agamic complexes included individuals with nucellar polyembryony associated to putatively neopolyploid, hexaploid cytotypes, while lower ploidy individuals were sexual and self-sterile. Higher genome sizes were also associated with larger pollen grains and stomata, besides other more complex morphological trends. Embryonic patterns were consistent for each site, individuals, and along years, although the percentage of polyembryonic seeds and number of embryos per seed varied. Monoembryonic sexual individuals were associated with higher elevation, allegedly last glacial maximum Cerrado refuges, while polyembryonic sporophytic apomicts appeared in lower areas.

Viability estimation and morphological characterization of pollen Datura suaveolens Willd (Solanaceae)

The species Datura suaveolens W. belongs to the family Solanaceae. It is a natural shrub species of the Himalayas, is widely distributed in South America and Brazil. In Brazil it is cultivated for medicinal and ornamental purposes. The objective of this work was to perform the morphological characterization and verify the pollen viability of the D. suaveolens species by means of colorimetric tests in order to determine the best dye for the species. Flower buds of Datura suaveolens were collected with occurrence in the municipality of Alta Floresta, MT. The experiment was carried out at the Cytogenetic and Tissue Culture Laboratory at the State University of Mato Grosso, Alta Floresta University Campus. For the estimation of pollen viability, three different dyes were evaluated: lugol, Alexander’s reactive and acetic orcein. For the pollen morphology, forty pollen grains stained with 3% safranin were analyzed. The morphological parameters analyzed were: equatorial diameter, polar diameter, size and shape and opening of the pollen grains. The diameter measurements were measured with the help of ImageJ software. The Alexander’s reactive is the most recommended colorimetric method for the pollen viability analysis of Datura Suaveolens because it revealed the highest average of viable pollen and presents a better visual distinction between viable and non-viable pollen. The Datura Suaveolens species has large pollen grains with Oblate-Spheroidal shape, the opening of the pollen is 3-pore type. The mean polar diameter of the species is 70.99 μm and the equatorial diameter is 67.94 μm.

Separation of the optical and mass features of particle components in different aerosol mixtures by using POLIPHON retrievals in synergy with continuous polarized Micro-Pulse Lidar (P-MPL) measurements

Abstract. The application of the POLIPHON (POlarization-LIdar PHOtometer Networking) method is presented for the first time in synergy with continuous 24/7 polarized Micro-Pulse Lidar (P-MPL) measurements to derive the vertical separation of two or three particle components in different aerosol mixtures, and the retrieval of their particular optical properties. The procedure of extinction-to-mass conversion, together with an analysis of the mass extinction efficiency (MEE) parameter, is described, and the relative mass contribution of each aerosol component is also derived in a further step. The general POLIPHON algorithm is based on the specific particle linear depolarization ratio given for different types of aerosols and can be run in either 1-step (POL-1) or 2 steps (POL-2) versions with dependence on either the 2- or 3-component separation. In order to illustrate this procedure, aerosol mixing cases observed over Barcelona (NE Spain) are selected: a dust event on 5 July 2016, smoke plumes detected on 23 May 2016 and a pollination episode observed on 23 March 2016. In particular, the 3-component separation is just applied for the dust case: a combined POL-1 with POL-2 procedure (POL-1/2) is used, and additionally the fine-dust contribution to the total fine mode (fine dust plus non-dust aerosols) is estimated. The high dust impact before 12:00 UTC yields a mean mass loading of 0.6±0.1 g m−2 due to the prevalence of Saharan coarse-dust particles. After that time, the mean mass loading is reduced by two-thirds, showing a rather weak dust incidence. In the smoke case, the arrival of fine biomass-burning particles is detected at altitudes as high as 7 km. The smoke particles, probably mixed with less depolarizing non-smoke aerosols, are observed in air masses, having their origin from either North American fires or the Arctic area, as reported by HYSPLIT back-trajectory analysis. The particle linear depolarization ratio for smoke shows values in the 0.10–0.15 range and even higher at given times, and the daily mean smoke mass loading is 0.017±0.008 g m−2, around 3 % of that found for the dust event. Pollen particles are detected up to 1.5 km in height from 10:00 UTC during an intense pollination event with a particle linear depolarization ratio ranging between 0.10 and 0.15. The maximal mass loading of Platanus pollen particles is 0.011±0.003 g m−2, representing around 2 % of the dust loading during the higher dust incidence. Regarding the MEE derived for each aerosol component, their values are in agreement with others referenced in the literature for the specific aerosol types examined in this work: 0.5±0.1 and 1.7±0.2 m2 g−1 are found for coarse and fine dust particles, 4.5±1.4 m2 g−1 is derived for smoke and 2.4±0.5 m2 g−1 for non-smoke aerosols with Arctic origin, and a MEE of 2.4±0.8 m2 g−1 is obtained for pollen particles, though it can reach higher or lower values depending on predominantly smaller or larger pollen grain sizes. Results reveal the high potential of the P-MPL system, a simple polarization-sensitive elastic backscatter lidar working in a 24/7 operation mode, to retrieve the relative optical and mass contributions of each aerosol component throughout the day, reflecting the daily variability of their properties. In fact, this procedure can be simply implemented in other P-MPLs that also operate within the worldwide Micro-Pulse Lidar Network (MPLNET), thus extending the aerosol discrimination at a global scale. Moreover, the method has the advantage of also being relatively easily applicable to space-borne lidars with an equivalent configuration such as the ongoing Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) on board NASA CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) and the forthcoming Atmospheric Lidar (ATLID) on board the ESA EarthCARE mission.

Induction of Tetraploids in Impatiens (Impatiens walleriana) and Characterization of Their Changes in Morphology and Resistance to Downy Mildew

Garden impatiens (Impatiens walleriana), a very important floricultural crop in the United States, has been devastated by impatiens downy mildew (IDM) in recent years. This study was conducted to determine if induced tetraploidy could improve impatiens resistance to downy mildew. Tetraploids were induced by colchicine and confirmed by chromosome counting. Compared with diploids, induced tetraploids showed significant morphological changes, including larger and thicker leaves with larger and fewer stomata; thicker and fewer stems; larger and fewer flowers; and larger pollen grains with higher stainability. In detached leaf and in vivo inoculation assays, tetraploids exhibited improved downy mildew resistance, with lower disease severity, disease incidences, and sporangia densities. Plasmopara obducens, the causal agent of IDM, underwent a similar development process in the leaf tissue of diploids and tetraploids. These results suggest that induced tetraploidy can result in significant changes in impatiens leaf and plant morphology and can increase impatiens resistance to downy mildew to a certain extent.

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

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

Screening A. ventricosa populations for 2n gametes

Sexual polyploidization via the formation of 2n gametes has been acknowledged as the most significant evolutionary mode of polyploidization among plant species. The present study was conducted in order to determine whether 2n gametes are present in the C-genome diploid Avena ventricosa Bal. ex Coss., a species that contributed to the evolution of the cultivated hexaploid species (Avena sativa L). Individual plants belonging to four different Cypriot populations, were screened for pollen grain size variation with the aim to distinguish 2n gametes. Avena ventricosa ARI00-845 was identified to produce large pollen grains at a low percentage (1.21%). Subsequent analysis using flow cytometry confirmed the presence of 2n gametes in the pollen. Cytogenetic analyses of pollen mother cells revealed cells with twice the typical chromosome number at metaphase I (i.e., 28 chromosomes). We postulate that irregularities in cell wall formation preceding meiosis could have contributed to the mode of chromosome doubling.

Pollen parameters estimates of genetic variability among newly selected Nigerian roselle (Hibiscus sabdariffa L.) genotypes

Estimates of some pollen parameters where used to assess the genetic diversity among some newly selected Nigerian Roselle (Hibiscus sabdariffa L.). Standard procedures were used to determine the pollen parameters such as: percentage pollen fertility, percentage pollen sterility, pollen diameters as well as anther diameters. The cytological results revealed significant (P ≤ 0.05) variation in the diameters of anther cap and pollen grains. Anther morphology and pollen grain morphology of the H. sabdariffa genotypes under light microscope showed fair diversity in the Anther and pollen grain sizes. The Roselle genotypes were grouped according to their anther sizes into small (< 400 μm), medium (400-700 μm) and large (> 700 μm); such character should be included in examining genetic diversity in this crop. The dendrogram produced from the cluster analysis of the different genotypes of the roselle based on diameters of the pollen grains and that of the anther cap-sizes also separate the genotypes into different groups. The results obtained in terms of percentage pollen fertility also showed some interesting variations. It is not untrue that larger pollen grain could serve as a better pollinizer than a smaller pollen grain; moreover, successes in crossing among such plants could be dependent on the sizes of the pollen. The pollen grain size variations obtained from this study is of good taxonomic value. The variation in the anther and pollen grain sizes could also be as a result of different genetic make of the Roselle genotypes and could serve as important diagnostic tool in differentiating Nigerian Roselle genotypes and achieving the cytotaxonomy of the crop. It is therefore concluded that there exist genetic variability among the pollen grains and anthers of the new selected Nigerian Roselle (H. sabdariffa) genotypes; these characters are good taxonomic parameters that could be used in evaluating genetic diversity of the crop in the study area. It is recommended that other pollen viability staining techniques should be employed to ascertain the level of the pollen fertility among the Roselle Genotypes. In addition, DNA-PCR technique should be used to further confirm the variability observed in this present study.Keywords: Anther Caps, Pollen diameters, Pollen fertility, Pollinizer, Variations, Dendrogram

Spines vs. microspines: an overview of the sculpture exine in selected basal and derived Asteraceae with focus on Asteroideae.

This study presents a detailed examination of the echinate and microechinate sculpturing in relation to the size of pollen grains in 31 selected species of Asteraceae belonging to the subfamilies Barnadesioideae, Mutisioideae, Carduoideae and Asteroideae. The aims were to recognize sculpturing patterns, under LM and SEM, within large and small pollen of both basal and derived species and to explore the features that could have taxonomic value to apply in palynological disciplines. The detailed examination of the exine surface showed both the relevance and limits of sculptural patterns for taxonomy. Under LM, the microechinate sculpture gave little taxonomic information, whereas in the echinate sculpture, three exine types and two subtypes were recognized. Type I included microechinate exine, which is commonly present in large pollen grains of the basal lineages. Types II (subtypes IIa and IIb) and III included echinate and smaller pollen grains. In these types, spines were always regularly arranged and, were characterized by the length, shape, tip, perforations and distribution. Type IIa included more or less conical spines usually with a distended base, less than 4µm in length, present in species of different tribes like Astereae, Eupatorieae, Helenieae, Gnaphalieae, Senecioideae and Heliantheae to a lesser extent. Type IIb includes slender spines with narrower bases, longer than 4µm, present in species of Coreopsideae, Heliantheae, Tageteae and Eupatorieae to a lesser extent. Type III included spines with swollen base, blunt tip and perforations over their entire surface. This type was present in only one of the basal species-Carduus thoermeri-and in one species of the derived tribe Helenieae, Gaillardia megapotamica. Probably, this is due to evolutionary convergence.

Poaceae Pollen from Southern Brazil: Distinguishing Grasslands (Campos) from Forests by Analyzing a Diverse Range of Poaceae Species.

This aim of this study was to distinguish grasslands from forests in southern Brazil by analyzing Poaceae pollen grains. Through light microscopy analysis, we measured the size of the pollen grain, pore, and annulus from 68 species of Rio Grande do Sul. Measurements were recorded of 10 forest species and 58 grassland species, representing all tribes of the Poaceae in Rio Grande do Sul. We measured the polar, equatorial, pore, and annulus diameter. Results of statistical tests showed that arboreous forest species have larger pollen grain sizes than grassland and herbaceous forest species, and in particular there are strongly significant differences between arboreous and grassland species. Discriminant analysis identified three distinct groups representing each vegetation type. Through the pollen measurements we established three pollen types: larger grains (>46 μm), from the Bambuseae pollen type, medium-sized grains (46–22 μm), from herbaceous pollen type, and small grains (<22 μm), from grassland pollen type. The results of our compiled Poaceae pollen dataset may be applied to the fossil pollen of Quaternary sediments.

Pollen morphology of Nothofagus (Nothofagaceae, Fagales) and its phylogenetic significance

Abstract Nothofagaceae (southern beeches) are a relatively small flowering plant family of trees confined to the Southern Hemisphere. The fossil record of the family is abundant and it has been widely used as a test case for the classic hypothesis that Antarctica, Patagonia, Australia and New Zealand were once joined together. Although the phylogenetic relationships in Nothofagus appear to be well supported, the evolution of some pollen morphological traits remains elusive, largely because of the lack of ultrastructural analyses. Here we describe the pollen morphology of all extant South American species of Nothofagus, using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy (LM), and reconstruct ancestral character states using a well-supported phylogenetic tree of the family. Our results indicate that the main differences between pollen of subgenera Fuscospora (pollen type fusca a) and Nothofagus (pollen type fusca b) are related to the size of microspines (distinguishable or not in optical section), and the thickening of colpi margins (thickened inwards, or thickened both inwards and outwards). In particular, Nothofagus alessandrii, the only extant South American species of subgenus Fuscospora, presents distinctive pollen features that have not been observed in any other species of the genus (i.e. a large granular infratectum and spongy apertural endexine). Species of subgenus Lophozonia are characterized by having the largest pollen grains, with polygonal outline in polar view, microspines distinguishable in optical section, long and non-thickened colpi, and a thin endexine. The reconstruction of character states for the node corresponding to the common ancestor to genus Nothofagus leads us to conclude that the ancestral form of Nothofagaceae should have had: equatorial diameter &lt; 40 μm, circular outline in polar view, microspines distinguishable in optical section, short colpi thickened inwards, and a thin endexine. These features are fully consistent with those present in Nothofagidites senectus Dettmann &amp; Playford, the oldest fossil species of Nothofagaceae recorded in Campanian-Maastrichtian sediments of Gondwana.

Pollen morphology of the tribe Sorbarieae (Rosaceae)

The pollen morphology of the tribe Sorbarieae (Adenostoma, Chamaebatiaria, Sorbaria, and Spiraeanthus) and two related genera Gillenia and Lyonothamnus was investigated by light, scanning electron, and transmission electron microscopy. Sorbarieae pollen was monad, tri-colporate, small to medium in size (P = 10.2–40.0 μm, E = 10.8–32.4 μm), and oblate to prolate in shape (P/E = 0.74–1.88). The sexine ornamentation was striate, but four different types could be divided: striate-psilate, striate-plicate, striate-microechinate, and striate-perforate. The pollen wall stratification typically consisted of unbranched columellae and a continuous endexine. As an additional palynological characteristic, orbicules (small sporopollenin granules) were observed in all taxa and thus a possible synapomorphic character of Sorbarieae as a whole. The pollen characteristics are useful to recognize certain taxa. Gillenia is the only genus with both a pore flap on the aperture and the perforated sexine. Lyonothamnus has a significantly thick exine and relatively larger pollen grains, which is compared to that of Sorbarieae. Some quantitative characteristics (e.g., pollen and colpus size, exine thickness, and ridge width of striae) identified using principal components analysis (PCA) may have diagnostic importance among the taxa in the tribe.

Can selection on a male mating character result in evolutionary change? A selection experiment on California wild radish, Raphanus sativus.

Whenever more pollen grains arrive on stigmas than necessary to fertilize ovules, sexual selection is possible. However, the role of sexual selection remains controversial, in part because of lack of evidence on genetic bases of traits and the response of relevant characters to selection. In an experiment with Raphanus sativus, we selected on tendency to sire seeds in the stylar or basal regions of fruits. This character is likely related to pollen tube growth rate, and seed position affects rates of abortion and seed predation. We measured differences among families in seed siring and related characters and evaluated responses to selection. All replicates showed strong effects of pollen donor family on proportion of seeds sired per fruit in mixed pollinations. Most also showed effects of pollen donor family on number of pollen grains per flower and pollen diameter. Two of four replicates showed a response to selection on position of seeds sired. In responding replicates, we found trade-offs in pollen grain size and number; plants with larger pollen grains sired more seeds in the basal region. Our data suggest a genetic basis for pollen donor ability to sire seeds in competition. The significant response to selection in two replicates shows that position of seeds sired can respond to selection. Thus, all components for sexual selection to occur and affect traits are present. Variation in results among replicates might be due to changes in greenhouse conditions. Environmental effects may contribute to the maintenance of variation in these fitness-related characters.

Blyxa kasaragodensis,a new species of Hydrocharitaceae from the ponds in the laterite plateau of Malabar coast, Kerala, India

A new aquatic species Blyxa kasaragodensis, collected from the ponds in the lateritc plateau of the Malabar coast, Kerala, India, is described and illustrated. This new species is similar to Blyxa octandra and Blyxa quadricostata in the dioecious nature, elongation of petals at the anthesis and in the number of stamens, but it shows many variations from the similar species such as purplish leaves, submerged male flowers, globular anther lobes, presence of compound pollen grain, large pollen grains, apetalous female flowers and long tail of the seeds. The pollination of Blyxa kasaragodensis takes place with the help of water and the mechanism is new to the genus Blyxa.

Toward a new rapid method to assess plant species in a bee pollen diet

Honey bee diet surveys require an accurate knowledge of the pollen supply and a rapid counting method for microscopic analyses. Referring to the literature, we aimed at reducing the number of pollen grains counted in order to decrease the time spent for each sample. For this, we compared counts on whole transects to alternative methods of counting by sub-sampling, using the non-acetolysed palynological method. For each pellet sample, a drop of a homogenized suspension was dried, degreased, and mounted onto a slide dressed with glycerol gelatin. The counting was performed through a digital camera fitted on a microscope. The study was carried out in two phases. Phase 1 was a test of slide homogeneity, carried out on a 10-slide set with one replicate. For each slide, we compared an exhaustive count of each present taxon on a whole transect divided in four quarters. Phase 2 was a search for an alternative counting method. The work was performed over the first six samples with replicates retaining exactly the same transect, but counting only one microscope field in three, then four, and finally one in five. Data analyses were carried out with Chi-square tests on taxa that were present in more than 5% of the sample. Phase 1 showed some cases of heterogeneity in microscope slides, leading to an error hazard when counting in a continuous mode up to a defined grain number. In phase 2, the comparison of alternative countings to full transects verified the linearity of the counting results. Suitable results were given by the reading method “one in three”. We improved the accuracy of this method for the particular case of samples containing large pollen grains, e.g., Zea mays, which are unevenly disseminated on the slide.

Morphological characterization and in vitro germination of heat-treated pollen in Eucommia ulmoides

AbstractPolyploid breeding has the potential to increase the economic secondary metabolites of Eucommia ulmoides. However, pollination with induced ploidy-mixed pollen has failed to produce polyploids (GAO, 2006). In this investigation, the morphological characterization and in vitro germination of heat-induced ploidy-mixed pollen of E. ulmoides were analysed to determine why there is no polyploid production. Heat-treated pollen grains were easily distinguished as large and small according to their length. The large pollen grains were significantly longer than both untreated and heat-treated small samples, suggesting that they were probably 2n pollen. Rather than the three germinal pores in small pollen, the large grains typically had four pores and, in some cases, shallow furrows, which might affect their germination. Although the maximal germination rates of the treated small and large pollen were not significantly different, the large pollen germinated tardily during the early stages of incubation. The small pollen maintained its growth during the incubation, but the tube growth of large pollen almost stopped after 24 h incubation. Both vegetative and generative nuclei in the large pollen moved into tubes later than in small pollen and the frequency of mitosis in generative nuclei of large pollen was low. Therefore, the tardy germination, poor tube growth, and weak activity of both vegetative and generative nuclei probably caused the poor competition of large pollen in certation. Finally, techniques to increase the competition of highploidy pollen and the prospect of 2n female gamete induction in the polyploid breeding program of E. ulmoides are discussed.

The Production of Tetraploid Swainsona formosa by Colchicine Mutagenesis

Swainsona formosa, a legume native to Australia, is a spectacular flowering plant that is used as a hanging basket, container or cut flower plant. Its breeding programme had been emphasized on the production of better flower quality through ploidy modification to produce tetraploid plants. Colchicine, an antimitotic chemical, had been sucessfully used to induce tetraploidyzation in S. formosa. Up to 50% of plants with double chromosome number (2n = 4x = 32) were produced by seedling application of colchicine at 0.01%–0.1%. Concentrations below 0.01% or above 0.1% were found not effective in inducing chromosome doubling. Tetraploid S. formosa were charaterized by larger leaflets, bigger size but lower density of stomata, larger flowers with longer peduncles and larger pollen grains with lower viability. In general, colchicine can be used effectively to induce polyploidyzation in S. formosa and this method should find application in breeding programme.

Flowering biology and pollen production of four species of the genus Rosa L.

Wild growing rose species are of great importance as a source of pollen for insects. Oil extracted from the petals of various &lt;em&gt;Rosa&lt;/em&gt; species is used in perfumery, cosmetic industry, and therapeutics. In our study, we compared the flowering duration and flower lifespan, the number of stamens and pistils, the mass and size of pollen grains as well as the anatomical features of the petals of four &lt;em&gt;Rosa&lt;/em&gt; species: &lt;em&gt;R. canina&lt;/em&gt;, &lt;em&gt;R. ×damascena&lt;/em&gt;, &lt;em&gt;R. gallica&lt;/em&gt;, and &lt;em&gt;R. rugosa&lt;/em&gt;. Moreover, we examined the pollen loads collected by bumblebees foraging on rose flowers in order to determine the attractiveness of pollen of this genus to insects. We showed the flower lifespan to vary (3.5–8 days) in the roses studied and revealed high variation in the number of stamens (82–260) and pistils (17–65) as well as in the mass of pollen produced. The flowers of &lt;em&gt;R. rugosa&lt;/em&gt; produced the highest amount of pollen (26.7 mg per flower), while the flowers of &lt;em&gt;R. canina&lt;/em&gt; the least (3.3 mg per flower), which is associated with differences in the number of stamens developed in the flowers between these species. The largest pollen grains were found in &lt;em&gt;R. &lt;/em&gt;×&lt;em&gt;damascena&lt;/em&gt; and &lt;em&gt;R. gallica&lt;/em&gt;. We demonstrated that &lt;em&gt;R. ×damascena&lt;/em&gt; produces the thickest petals and that scent-emitting papillae found on the adaxial surface of the petals differ in size and shape in the rose species investigated.