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Journal articles on the topic 'Pollen grain size'
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Hao, Kai, Zhi-Xi Tian, Zi-Chen Wang, and Shuang-Quan Huang. "Pollen grain size associated with pollinator feeding strategy." Proceedings of the Royal Society B: Biological Sciences 287, no. 1933 (2020): 20201191. http://dx.doi.org/10.1098/rspb.2020.1191.
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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.
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De Freitas, Jéssica Mena Barreto, Andrielle Wouters Kuhn, Viviane Dal-Souto Frescura, Liliana Essi, and Solange Bosio Tedesco. "Differences in stomatal and pollen grain dimensions and pollen viability between Paspalum rawitscheri populations." Ciência e Natura 42 (June 29, 2020): e46. http://dx.doi.org/10.5902/2179460x40749.
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The objective of this study was to evaluate stomatal and pollen grain size and to estimate pollen viability of individuals from different populations of Paspalum rawitscheri (Parodi) Chase ex G.H. Rua Valls. To analyze stomatal size, slides were made of the adaxial leaf epidermis using the epidermal impression method. The height and width of 100 stomata per population were analyzed. Pollen was obtained from inflorescences to evaluate pollen grain size and pollen viability. Pollen grains were stained with 2% acetic orcein, 2% acetic carmine, or Alexander’s reactive stain. Per population, 1600 grains of pollen were observed for viability, and 50 grains of pollen were measured. There were significant differences between populations in stomatal height and pollen grain height and width. The populations also differed in pollen viability, with the Santa Maria population showing the lowest viability. The differences in stomatal and pollen grain size suggest genetic variability in the evaluated populations. Moreover, low pollen viability in one population indicates that its decline may be related to low fertility. Keywords: Grass. Ploidy. Fertility. Threatened species.
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Pietarinen, Päivi, and Hanna-Leena Pasonen. "Pollen performance and male fitness in an anemophilous, monoecious tree, Betula pendula." Canadian Journal of Botany 82, no. 9 (2004): 1284–91. http://dx.doi.org/10.1139/b04-069.
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Betula pendula Roth clones were examined to study the relationship between pollen grain size and pollen tube growth rate and pollen and seed performance. Two hypotheses were tested: (i) pollen donors with larger pollen grains have faster growing pollen tubes and (ii) maternal plants produce more seeds when inflorescences have been pollinated by pollen from donors with fast pollen tube growth. Pollen from 15 plants was collected, and pollen grain sizes and pollen tube growth rates were studied in vitro. Eight maternal clones were pollinated by pollen from seven paternal clones, pollen tube growth rates of the pollen donors were measured on each maternal plant, and the number and mass of the resulting seeds were analysed. There was no correlation between pollen grain size and pollen tube growth rate in vitro. Also, there was no relationship between pollen tube growth rate and the number of produced or aborted seeds. Thus, the hypothesis that larger pollen grains would have longer pollen tubes was not supported by the present study. The results of the present study do not support the idea that pollen donors with fast pollen tube growth should sire more and better seeds.Key words: Betula pendula, female choice, nonrandom abortion, pollen competition, sexual selection.
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khalik, Kadry Abdel, Suad Al Ruzayza, Abdullah Assiri, and Ahmed Elkordy. "Pollen morphology of Malvaceae genera from Saudi Arabia and its taxonomic significance." MAY 2021, no. 15(05):2021 (May 10, 2021): 725–42. http://dx.doi.org/10.21475/ajcs.21.15.05.p3129.
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Pollen morphology of 20 species belong to seven genera (Abutilon, Althaea, Hibiscus, Malva, Pavonia, Senra and Sida) of Malvaceae from Saudi Arabia were studied by using light microscope (LM) and scanning electron microscope (SEM). Quantitative and qualitative pollen morphological characters which vary among investigated taxa are found in the pollen polarity, symmetry, size, shape, polar axis, equatorial diameter, P/E ratio, average height and width of spine, aperature character and spine index. The pollen grains vary from spheroidal, prolate spheroidal, oblate spheroidal to suboblate. All taxa were characterized by relatively large to medium sized pollen grains, numerous pores scattered irregularly all over the grain, and echinate sculpturing. Sida ovata is the largest size pollen grain (138.95) µm. On the other hand, Malva parviflora showed the smallest pollen size (52.28 µm). The average height and width of spine varied greatly among studied taxa. The highest spines (20.65µm) found in Sida ovata, while the shortest (3.19 µm) was found in Abutilon pannosum. Results of the pollen shape, size, and exine sculpture characters offered useful data for evaluating the taxonomy of Malvaceae both on subgeneric and sectional levels. A key for the identification of the investigated taxa based on pollen grains characters is also provided
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Sosnoskie, L. M., T. M. Webster, D. Dales, G. C. Rains, T. L. Grey, and A. S. Culpepper. "Pollen Grain Size, Density, and Settling Velocity for Palmer Amaranth (Amaranthus palmeri)." Weed Science 57, no. 4 (2009): 404–9. http://dx.doi.org/10.1614/ws-08-157.1.
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Palmer amaranth is resistant to several herbicides, including glyphosate, and there is concern that the resistance traits can be transferred between spatially segregated populations via pollen movement. The objective of this study was to describe the physical properties of Palmer amaranth pollen, specifically size, density, and settling velocity (Vs), that influence pollen flight. The mean diameter for Palmer amaranth pollen, as determined by light microscopy, was 31 µm (range of 21 to 38 µm); mean pollen diameter as measured with the use of an electronic particle sizer was 27 µm (range of 21 to 35 µm). The mean density of the solid portion of the pollen grain was 1,435 kg m−3. Accounting for the density of the aqueous fraction, the mean density of a fully hydrated pollen grain was 1,218 kg m−3. By Stokes's law, the estimated mean theoreticalVsfor individual Palmer amaranth pollen grains was 3.4 cm s−1for the range of pollen diameters with a mean of 31 µm and 2.6 cm s−1for the range of pollen diameters with a mean of 27 µm. Results from laboratory studies indicated the majority of single pollen grains settled at a rate of 5.0 cm s−1. The difference between the theoretical and empirical estimates ofVswas likely due to changes in pollen density and shape postanthesis, which are not accounted for using Stokes's law, as well as the presence pollen clusters.
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Tejaswini. "Male gametophytic generation and a possible approach for selective pollination in carnation (Dianthus) breeding program." Plant, Soil and Environment 48, No. 8 (2011): 368–75. http://dx.doi.org/10.17221/4382-pse.
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Present study focuses on making best possible use of male gametophytic generation in carnation breeding program. Exploration of pollen population revealed the existence of variability in terms of pollen morphology and histochemical content among as well as within varieties and species of Dianthus caryophyllus and D. chinensis sufficient to make selection. Pollen grain size and histochemical content were found to be associated with germination capacity and pollen tube growth rate. In addition, pollen germination capacity and elongation of pollen tube in response to presence of culture filtrate from F. oxysporum. f.sp. dianthi causal organism of fusarium wilt in carnation was found to be governed by pollen grain size and histochemical content of pollen grains. Entire result suggests the possibility of selecting the desired pollen grains from a pollen population and possibility of attempting selective pollination in carnation breeding program.
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Shi, Yinping, Qiangsheng Wang, Jianming Yang, Congyi Sui, and Qingrong Sun. "493 Inducing Polyploidy Pollen in Apple Cultivars." HortScience 34, no. 3 (1999): 530B—530. http://dx.doi.org/10.21273/hortsci.34.3.530b.
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To perform apple polyploid breeding the ways of inducing polyploidy pollen with temperature and chemicals were studied. Materials include 13 diploid cultivars: Red Chief, Dai Hong, Rose Red, Golden Delicious, Mollie's Delicious, Gala, Bella, Jonathan, Fuji, Qiu Kou Hong, and Yan Qing, OBIR-2T-47. Chemicals: Chloroform, N-nitroso-ethylurea. At the beginning of PMC meiosis, fruiting branching groups were covered with plastic bags to raise temperature or were treated with chemical. After covering, temperature during the day increased 2 °C, generally not lower than 0 °C. Whether branches received high temperature or chemicals treatment, polyploidy pollen was induced to produce. The pollen grain of CK is tricolporat, its polar view is triangular, and its diameter almost 40 μm, showing no difference in size. Rate of empty pollen grain is low. Pollen grains that were treated were different in size, and rate of empty pollen is high, part of pollen grains germinating colporat change into tetracolporat with a few polycolporat, its polar view is square, round, and oval. The diameter of large pollen grains was 45-48 μm, increased by 11-12%. Giant pollen grain are 50-68 μm, increased by 25%-70%. Rate of induction is different in different cultivars. For most cultivars, giant pollen grain is 0.3%-0.5%. Gala and OBIR-2T-47 were higher, reaching 2.5%-7%. Chemicals caused damage on cultivars. Delicious strains were easily damaged.
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Zhuikova, Tatyana Valerievna, Anna Andreevna Kovalenko, and Anna Vladimirovna Mezina. "Variability of male gametophyte traits in morphological forms of Taraxacum officinale Wigg. s.l. under conditions of technogenic soil transformation." Samara Journal of Science 10, no. 2 (2021): 31–39. http://dx.doi.org/10.17816/snv2021102104.
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The paper studies endogenous, individual and group variability of the traits pollen grain fertility and size of fertile pollen grains among two morphological forms of Taraxacum officinale Wigg. s.l., growing in coenopopulations in the gradient of technogenic soil transformation. The study area is the Pritagil zone of the Middle Urals (Nizhny Tagil city, Sverdlovsk Region, N 58, E 60). It was found that the studied morphological forms of dandelion in most cases are characterized by average endogenous, individual and group variability of the trait pollen grain fertility and low endogenous and individual variability of the trait pollen grain size. The group variability for this trait is medium and low. The endogenous variability of pollen grain fertility and size among f. dahlstedtii on agrozems is slightly higher than on technozems. Among f. pectinatiforme the endogenous variability of pollen grain fertility is higher on agrozems only. An increase in the level of soil contamination on agrozems leads to a decrease in the endogenous variability of pollen grain fertility among both forms of dandelion. On technozems a similar reaction is expressed only among f. pectinatiforme . The analysis of the studied trait in the entire gradient of technogenic soil transformation indicates a significant influence of this factor only on the endogenous variability of pollen grain fertility among f. dahlstedtii . Despite the absence of statistically significant differences in the individual variability of the pollen grain fertility trait between dandelion forms, on average, the coefficients of its variation on agrozems are lower among f. dahlstedtii , and on technozems - among f. pectinatiforme . The same conclusion applies to the individual variability of the trait size of fertile pollen grains. In general, among f. dahlstedtii the coefficients of variation of the studied signs of the male gametophyte are lower in agrozems than in technozems, among f. pectinatiforme the picture is reversed. On average, the proportion of plants with low ( C ᵥ 11%) individual variability in pollen grain fertility among f. dahlstedtii out of all the studied coenopopulations is 43,3% versus 61,7% among f. pectinatiforme . The influence of technogenic transformation of the environment is manifested in an increase in the proportion of f. pectinatiforme plants with a low level of variability of the studied traits in the coenopopulations of the buffer and impact zones. Among f. dahlstedtii the reverse pattern is characteristic only for pollen fertility. The group variability of pollen grain fertility in both agrozems and technozems is higher among f. dahlstedtii . With an increase in pollution on agro-soils, this indicator increases among both forms of dandelion, and decreases in technozems. There is a tendency to increase the group variability of pollen grain fertility among plants of both forms of T . officinale on technozems. An increase in the level of soil contamination on agrozems leads to an increase in the group variability of the trait size of fertile pollen grains among f. dahlstedtii and a decrease among f. pectinateforme . On technozems the opposite effect is noted. In general, the group variability of the studied trait among plants of both morphological forms of dandelion on agrozems is higher than on technozems.
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Atlagic, Jovanka, Ana Marjanovic-Jeromela, Radovan Marinkovic, and Sreten Terzic. "Pollen grain traits of oil species from the Novi Sad collection." Genetika 41, no. 3 (2009): 263–70. http://dx.doi.org/10.2298/gensr0903263a.
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The collection of oil species in Novi Sad contains 12 species represented with 1-4 cultivars or landraces. In the continuous work on this collection in the sense of breeding of some of those species and their usage as a source of 'desirable genes' we analyzed pollen grain morphology (shape and size), as well as pollen viability. To determine mentioned pollen traits we used Axiovert 40C microscope together with a software package (AxioVision LE; Rel.4.3.) for measurement of pollen length and width. Pollen viability was determined using a staining method (ALEXANDER, 1969). The results showed that species differ by pollen grain shape (round, egg-shaped, triangular and rod) as well as by shape of exine (thick and spiky, thick to thin). In some species there was a specific number of apertures present (1-11). The size of viable pollen grains ranged from 29,10/12,58? (coriander) to 176,63/169,94? (oil gourd), while non-viable pollen grains were always smaller (27,27/10,97? to 119,62/100,86?) at the same plant species. Pollen viability of most species was around 80%. Lowest pollen viability was found in white flax (56,98%), and the highest in oil pumpkin (91,43%).
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AROGUNDADE, Oluwabunmi Okerinmola, and Hameedat O. LAWAL. "Palynological Studies of Three Taxa and One F1 Hybrid in the Genus Talinum Adans." Notulae Scientia Biologicae 10, no. 2 (2018): 175–81. http://dx.doi.org/10.15835/nsb10210214.
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Acetolysed pollen grains of Talinum paniculatum (Jacq.) Gaertn., Talinum triangulare (Jacq.) Willd. pink petals, Talinum triangulare (Jacq.) Willd. white petals and Talinum triangulare (Jacq.) Willd. pink and white petals F1 hybrid were studied in order to document their morphological structures and ascertain features of taxonomic significance among them. All the taxa have generic features which support their classification as a genus as well as distinct features which ascertain their individuality. Generic features include monad pollen unit, acolpate and monocolpate pollen grains as well as circular and ovate pollen shapes. The delimiting features include additional dyads pollen units in T. triangulare white petal and the F1 hybrid of T. triangulare pink and white petals, quadrangular pollen shape in T. paniculatum, bicolpate pollen grain in the F1 hybrid, tricolpate pollens in T. triangulare white petal and T. paniculatum, tetracolpate pollens in T. triangulare pink petal and T. paniculatum and pentacolpate pollen grains in T. paniculatum only. The shape of the pores in T. paniculatum also separated it from the varieties and hybrid of T. triangulare. Based on the pollen size, the pollens of T. paniculatum are Media (25 - 50 µm) while those of the two varieties of T. triangulare and their F1 hybrid are Magna (50 - 100 µm). The taxa of Talinum in this study can be separated based on their palynological features.
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Membrives, N., J. Martín, J. Caujapé-Castells, and J. Pedrola-Monfort. "Pollen morphology and biometry of the genus Androcymbium (Colchicaceae) in southern Africa: taxonomic and biogeographic considerations." Bothalia 32, no. 1 (2002): 91–96. http://dx.doi.org/10.4102/abc.v32i1.471.
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Pollen characters in 16 southern African type specimens of Androcymbium Willd. that represent the three sections into which the genus is presently divided (Androcymbium, Dregeocymbium and Erythrostictus), were examined to assess the possibility of sectional characterization based on pollen traits and to explore the relationship between pollen traits and geographic species distribution. Differences in pollen grain size, shape, number of apertures and exine pattern, were observed. Principal Component Analysis, using both qualitative and biometric pollen characters, distinguished four groups of species with four different pollen types. Most of the species have a microreticulate exine pattern with either diaperturate or tria- perturate grains. The remaining species have either a rugulate exine pattern with diaperturate grains, or a rugulate-reticu- late exine pattern with thickened (hypertrophied) muri with diaperturate grains. While section Dregeocymbium can be well delimited by the unique thickened muri. and by a significantly larger grain size, no diagnostic pollen traits were found for sections Androcymbium and Erythrostictus. Similarly, although the six northern African species exhibit a microreticulate exine pattern, the high variability observed for this trait in their southern African counterparts, does not follow a geographic pattern.
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Price, Leslie D., F. Chukwuma, and J. J. Adamczyk. "Honey Bee (Hymenoptera: Apidae) Pollen Load Rate Based on Pollen Grain Size." Journal of Entomological Science 39, no. 4 (2004): 677–78. http://dx.doi.org/10.18474/0749-8004-39.4.677.
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Morgan, J. M. "Pollen grain expression of a gene controlling differences in osmoregulation in wheat leaves: a simple breeding method." Australian Journal of Agricultural Research 50, no. 6 (1999): 953. http://dx.doi.org/10.1071/ar98143.
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The possibility that a gene conditioning differences in osmoregulation in wheat leaves (or) is also expressed in pollen grains was investigated in order to differentiate heterozygous and homozygous lines for use in backcross breeding. The difference in osmoregulation in leaves was expressed as a difference in solute accumulation which was calculated from responses of osmotic potential and relative water content to reductions in water potential caused by droughting plants in pots. A corresponding allelic difference was found in pollen grains. It was demonstrated by a difference in relative size, and solute accumulation, after stressing using polyethelene glycol solution. The response occurred only after addition of a small quantity of potassium chloride, and the maximum response occurred at concentrations of approximately ≥0.2 mM (at least to 10 mM). This suggests that or may condition high affinity potassium transport. Single-gene control was confirmed using pollen responses, and pollen grain expression was further demonstrated by the use of pollen responses, to identify alleles and thus manipulate leaf responses in a backcross breeding study. Because the differences in pollen grain size may be readily observed without measurement using a microscope with relatively low magnification, and because the pollen grains are easily sampled at flowering, the pollen response is suitable as a routine test in plant breeding involving pedigree or backcross methods.
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Stone, Elizabeth A., Chamari B. A. Mampage, Dagen D. Hughes, and Lillian M. Jones. "Airborne sub-pollen particles from rupturing giant ragweed pollen." Aerobiologia 37, no. 3 (2021): 625–32. http://dx.doi.org/10.1007/s10453-021-09702-x.
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AbstractRagweed pollen is a prevalent allergen in late summer and autumn, worsening seasonal allergic rhinitis and asthma symptoms. In the atmosphere, pollen can osmotically rupture to produce sub-pollen particles (SPP). Because of their smaller size, SPP can penetrate deeper into the respiratory tract than intact pollen grains and may trigger severe cases of asthma. Here we characterize airborne SPP forming from rupturing giant ragweed (Ambrosia trifida) pollen for the first time, using scanning electron microscopy and single-particle fluorescence spectroscopy. SPP ranged in diameter from 20 nm to 6.5 μm. Most SPP are capable of penetrating into the lower respiratory tract, with 82% of SPP < 1.0 μm, and are potential cloud condensation nuclei, with 50% of SPP < 0.20 μm. To support predictions of the health and environmental effects of SPP, we have developed a quantitative method to estimate the number of SPP generated per pollen grain ($${n}_{\mathrm{f}}$$ n f ) based upon the principle of mass conservation. We estimate that one giant ragweed pollen grain generates 1400 SPP across the observed size range. The new measurements and method presented herein support more accurate predictions of SPP occurrence, concentration, and air quality impacts that can help to reduce the health burden of allergic airway diseases. Graphic abstract Rupturing ragweed pollen releasing cellular components (right), viewed by an inverted light microscope.
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PLATA, ANGELO, and SANTIAGO GUZMÁN-GUZMÁN. "POLLEN MORPHOLOGY OF Ombrophytum villamariensis (BALANOPHORACEAE)." Phytotaxa 472, no. 1 (2020): 74–78. http://dx.doi.org/10.11646/phytotaxa.472.1.10.
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This study contributes to the morphological characterization of Ombrophytum villamariensis, a new species of Neotropical Balanophoraceae recently described for Colombia. The study revealed the presence of diagnostic characters in the pollen grain such as small size and a circular endoaperture. Unlike other species, only tricolporate pollen grains were observed.
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Božič, Anže, and Antonio Šiber. "Mechanical design of apertures and the infolding of pollen grain." Proceedings of the National Academy of Sciences 117, no. 43 (2020): 26600–26607. http://dx.doi.org/10.1073/pnas.2011084117.
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When pollen grains become exposed to the environment, they rapidly desiccate. To protect themselves until rehydration, the grains undergo characteristic infolding with the help of special structures in the grain wall—apertures—where the otherwise thick exine shell is absent or reduced in thickness. Recent theoretical studies have highlighted the importance of apertures for the elastic response and the folding of the grain. Experimental observations show that different pollen grains sharing the same number and type of apertures can nonetheless fold in quite diverse fashions. Using the thin-shell theory of elasticity, we show how both the absolute elastic properties of the pollen wall and the relative elastic differences between the exine wall and the apertures play an important role in determining pollen folding upon desiccation. Focusing primarily on colpate pollen, we delineate the regions of pollen elastic parameters where desiccation leads to a regular, complete closing of all apertures and thus to an infolding which protects the grain against water loss. Phase diagrams of pollen folding pathways indicate that an increase in the number of apertures leads to a reduction of the region of elastic parameters where the apertures close in a regular fashion. The infolding also depends on the details of the aperture shape and size, and our study explains how the features of the mechanical design of apertures influence the pollen folding patterns. Understanding the mechanical principles behind pollen folding pathways should also prove useful for the design of the elastic response of artificial inhomogeneous shells.
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Frizon, Patrícia, Sandra Patussi Brammer, Carolina Cardoso Deuner, Amanda Chechi, Maria Imaculada Pontes Moreira Lima, and Pedro Luiz Scheeren. "Genetic stability in interspecific hybridizations of wheat populations determined by meiotic index and pollen viability." Biotemas 34, no. 2 (2021): 1–9. http://dx.doi.org/10.5007/2175-7925.2021.e79666.
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The objective of this study was to evaluate genetic stability by determining the meiotic index (MI) and pollen viability in F1RC2 segregating populations, obtained by the crosses between wheat commercial cultivars and synthetic wheat, aimed at introgression/genetic resistance. For MI, three ears were collected per genotype, before anthesis, and they were fixed in Carnoy’s solution. The cytological slides were prepared by crushing the anthers and staining with 1% acetocarmine, and the normal tetrads and the ones with micronuclei were observed under a light microscope. For pollen viability, the ears were collected at the stage of mature pollen grain. The methodological procedure was similar to that of the tetrads, evaluating the pollen grains as viable, with little starch, with two pores, different sizes and non-viable. The pollen grain size was measured by the Axion Vision software. All the segregating populations with MI above 90% and high pollen viability (above 85%) reflected a stable meiotic behavior. About the variation in size, the CIGM90.909/BRS 179 cross showed pollen grains with 58.43 μm and CIGM93.298/BRS Guamirim, 47.15 μm. According to the results, wheat segregating populations were considered meiotically stable and suitable for use in wheat breeding programs and for incorporation of new important genes.
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Katsiotis, A., and R. A. Forsberg. "Pollen grain size in four ploidy levels of genusAvena." Euphytica 83, no. 2 (1995): 103–8. http://dx.doi.org/10.1007/bf01678036.
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Aizen, Marcelo A., and Estela Raffaele. "FLOWERING-SHOOT DEFOLIATION AFFECTS POLLEN GRAIN SIZE AND POSTPOLLINATION POLLEN PERFORMANCE INALSTROEMERIA AUREA." Ecology 79, no. 6 (1998): 2133–42. http://dx.doi.org/10.1890/0012-9658(1998)079[2133:fsdapg]2.0.co;2.
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Yang, Shixiong, Zhuo Zheng, Kangyou Huang, et al. "Modern pollen assemblages from cultivated rice fields and rice pollen morphology: Application to a study of ancient land use and agriculture in the Pearl River Delta, China." Holocene 22, no. 12 (2012): 1393–404. http://dx.doi.org/10.1177/0959683612449761.
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Pollen from a series of surface soil samples collected along a transect spanning southeast China was investigated to better understand palynological signals of ancient agriculture and other human activity. The transect surface samples consist of pairs taken inside and outside rice paddy fields. Pollen assemblages from these samples are valuable as modern analogs of human-altered environments and rice agriculture. Our measurements of Poaceae pollen grains from inside the modern rice fields discovered that 34–40 µm is the statistically significant size range for identifying domesticated rice in fossil pollen samples. This conclusion is also based on a size comparison of raw and chemically treated modern pollen grains from the plants. Pollen measurements for local wild grasses show that most native weeds have pollen grains less than 30 µm in size. The modern analogs and our study of the influence of chemical treatment on pollen grain size made it possible to examine a sediment core from the Pearl River delta for evidence of anthropogenic influence, including rice farming. Pollen assemblages from around 2200 cal. yr BP are highly similar to those of our modern analogs representing disturbed landscapes outside modern rice fields. The pollen spectra reveal abrupt increases in Poaceae, Dicranopteris, Artemisia and Pinus indicative of rice farming and forest clearance, at around 2200 cal. yr BP. Major factors associated with this abrupt transition were the rapid formation of the deltaic flood plain and massive increases in the Pearl River delta area population during the Qin Dynasty.
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Yasniuk, М. V., О. A. Kaminska, and V. V. Rodinkova. "Grass pollen morphology investigation as a basis for monitoring of allergenic biological particles in an automatic mode." Reports of Morphology 26, no. 2 (2020): 32–38. http://dx.doi.org/10.31393/morphology-journal-2020-26(2)-05.
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A clear distinction between the morphology of allergenic pollen grains of various genera of the Poaceae family is an important task in determining the causal allergenic factors in the population. It allows significant improvement of the efficiency of seasonal allergy diagnostics caused by grass pollen. Moreover, it let to perform better predictions of allergenic risks for people, suffering from pollinosis caused by Poaceae pollen. Therefore, the aim of our study was to establish the morphological difference between the pollen grains of plants of various species of Poaceae family in order to further determination of the possibility to use the established distinctions for the identification of pollen in aerobiological studies. For this, both herbarium samples and pollen of the studied plants were collected in the field during May-June 2019 in Vinnytsia. The pollen was shaken off the anthers directly onto a glass slide, immediately stained with basic fuchsin, and covered with a cover slip. The sizes of pollen grains – their width and length – were determined and analyzed using the PhotoM 1.21 program, and the obtained data on the sizes of pollen were divided into categories by the quartile method in Excel. Three categories of pollen sizes were identified: large, medium and small. Large grains had width and length parameters of 40 μm or more, average grains ranged from 26 to 39 μm, and small grains had a size of 26 μm or lesser in width and length. The large category includes the pollen of Hordeum morinum (39.5-53.1 μm), Elytrigia repens (41-48 μm), Secale cereale (48.4-62.5 μm) and Bromus arvensis (42.2-52.7 μm). The medium grain category included pollen from Dactylis glomerata (29.2-38.1 μm), Poa spp. (26.1-37.3 μm), Panicum capillare (33.3-39.5 μm), Lolium perenne (30.4-35.3 μm), Bromus sterilis (28.3-30.8 μm). The pollen size of B. ramosus ranged from 26.1 to 39.5 µm, and B. tectorum was from 35 to 38.4 µm. The pollen grains of Poa pratense (22.1-25.9 μm) and Piptatherum spp were assigned to the category of the smallest pollen (20.3-24.1 microns). Agrostis gigantea was the only grass pollen type whose size fitted for each category. We found out large, medium-sized and grains of 25.0-27.7 microns, which lie between categories 2 and 3, for different populations of this plant. Consequently, some genera and species of Poaceae can be distinguished by the size of their pollen, while in others the size of pollen grains varies considerably. It is necessary to carry out further research that will help to establish the morphology of pollen of a larger number of Grass family plants. This will significantly improve the diagnosis and prevention of seasonal allergy caused by grass pollen in Ukraine.
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Lau, Tak-Cheung, and Andrew G. Stephenson. "EFFECTS OF SOIL NITROGEN ON POLLEN PRODUCTION, POLLEN GRAIN SIZE, AND POLLEN PERFORMANCE IN CUCURBITA PEPO (CUCURBITACEAE)." American Journal of Botany 80, no. 7 (1993): 763–68. http://dx.doi.org/10.1002/j.1537-2197.1993.tb15292.x.
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Aizen, Marcelo A., and Estela Raffaele. "Flowering-Shoot Defoliation Affects Pollen Grain Size and Postpollination Pollen Performance in Alstroemeria aurea." Ecology 79, no. 6 (1998): 2133. http://dx.doi.org/10.2307/176716.
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Soldatova, Viktoria Yurievna, and Algystaana Petrovna Samsonova. "The influence of urban environment on pollen grains of the silver birch (Betula pendula Roth) in conditions of Yakutsk." Samara Journal of Science 8, no. 3 (2019): 80–84. http://dx.doi.org/10.17816/snv201983113.
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This paper studies variability of pollen grains of the silver birch in relation to the quality of urban environment. The material was collected in 12 sites. A total of 1,190 leaves and 24,000 pollen grains were examined and measured. The pollen fertility varied within 69-92%. Statistically significant decrease in fertility was observed in conditions of high-intensity traffic load, in the central area of the city, and where the road surface was in poor condition. Under the same conditions a statistically significant increase in percentage of relatively fertile pollen grains is observed. We found significant correlation between the level of fluctuating asymmetry (FA) and the share of fertile and half-fertile pollen grains. For fertility Spearmans rho was -0,71; and for half-fertility, r = 0,66, p 0,05. A similarly significant correlation (r = -0,7, p 0,05) was found between the diameter of pollen grains and traffic load, which indicates a consistent organism response to environment deterioration. From the above, it follows that for assessment of environmental condition such characteristics of pollen grains as fertility, half-fertility, and pollen grain size can be used.
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MÜNTZING, ARNE. "CHROMOSOME NUMBER, NUCLEAR VOLUME AND POLLEN GRAIN SIZE IN GALEOPSIS." Hereditas 10, no. 3 (2010): 241–60. http://dx.doi.org/10.1111/j.1601-5223.1928.tb02473.x.
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Fivawo, N. C., and H. Rees. "Chromosome size variation during pollen grain development in Scilla sibirica." Theoretical and Applied Genetics 70, no. 4 (1985): 417–21. http://dx.doi.org/10.1007/bf00273748.
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Fallah, Fahimeh, and Farrokh Ghahremaninejad. "Palyno-morphology of Hedera L. (The ivy genus, araliaceae) and their systematics implications." Genetika 53, no. 2 (2021): 851–65. http://dx.doi.org/10.2298/gensr2102851f.
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The palynomorphological characteristics of 5 species belonging to Hedera of the Araliaceae family were studied in detail. These plant species were collected from various phytogeographical regions of Iran and Hungary. The palynological investigation was accomplished using Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). Pollen grains of the species are reticulate, prolate, sub-prolate, tricolporate, isopolar, radially symmetrical, and monad. The largest pollen grain was in the Hedera colchica species (72.24?1.6 ?m) and the smallest pollen grain was in Hedera helix (28.63?2.1 ?m). The research carried out by the TEM showed that the species were different in terms of exine thickness, tectum thickness, foot layer thickness, the diameter and length of the Columella, the thickness and shape of the Caput, the tectum to foot layer )T/F( ratio, the absence or presence of the Endexine and the thickness of the Intine layers. The main purpose of this study was the importance of the relationship between pollen grain size and the number of chromosomes and ploidy level in Hedera species.
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Bykowska, Joanna, and Małgorzata Klimko. "Pollen Morphology of Pinus mugo Turra × Pinus sylvestris L. Hybrids and Parental Species in an Experimental Culture." Acta Biologica Cracoviensia s. Botanica 57, no. 1 (2015): 149–60. http://dx.doi.org/10.1515/abcsb-2015-0009.
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Abstract Pollen grains of Pinus mugo, P. sylvestris and P. ×rhaetica (= P. mugo × P. sylvestris) were examined by light and scanning electron microscopy. The pollen grains were bisaccate and monosulcate. The corpus-saccus attachment was distinct. The pollen corpus exine sculpture was verrucate-rugulate and deeply sculptured. The surface of the tectum was covered with small grana and it was perforate. The saccus sexine ornamentation was reticulate and irregularly perforate. The tectum surface characters in the proximal and distal view of the corpus and saccus were less variable and they did not provide good criteria to identify the species under study. However, some differences were observed in the size of elevation on the corpus between pollen grains of the same species and between the parental species. This study of the pollen grain morphology of the corpus and saccus provided some important new data.
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Sousa, V. A., and H. H. Hattemer. "Pollen dispersal and gene flow by pollen in Araucaria angustifolia." Australian Journal of Botany 51, no. 3 (2003): 309. http://dx.doi.org/10.1071/bt02037.
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Araucaria angustifolia (Bert.) O.Ktze. is an economically important tree in southern Brazil. Indiscriminate exploitation is threatening this species with extinction. Conservation programs are urgently needed to save the remaining forest, and such programs must be guided by biological studies that genetically characterise the remaining populations. Pollen and seed dispersion patterns determine the distance of gene flow and directly influence genetic structure and effective population size. A. angustifolia is a wind-pollinated dioecious tree. For pollen-dispersal airflow, physical characteristics of pollen grain, such as size and shape, must be considered. The aim of this work was to determine the homogeneity of effective pollen clouds as well as to infer the physical characteristics of pollen. The homogeneity of pollen clouds of A. angustifolia was assessed for 70 trees of natural population in Brazil. Analysis of genetic variability and differentiation of the effective pollen clouds detected high diversity at the MDH-B and 6-PGDH-B loci. Heterogeneity G-tests indicated pollen pool heterogeneity in four of seven examined loci (GOT-B, PGM-A, SKDH-B and 6-PGDH-B). The pollen grains measured 61.50 μm. The floating rate ranged from 12.02 to 18.98 cm s–1. The physical characteristics of the pollen suggest that pollen dispersion is likely to be limited.
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Vieira, Lívia de Jesus, Taliane Leila Soares, Mônica Lanzoni Rossi, Alfredo Augusto Cunha Alves, Francisco de Assis Ribeiro dos Santos, and Fernanda Vidigal Duarte Souza. "Viability, production and morphology of pollen grains for different species in the genus Manihot (Euphorbiaceae)." Acta Botanica Brasilica 26, no. 2 (2012): 350–56. http://dx.doi.org/10.1590/s0102-33062012000200011.
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The objective of this work was to characterize the viability, production and morphology of pollen for different species in the genus Manihot. Floral buds from Manihot accessions were collected from two germplasm banks at Embrapa Cassava & Fruits. The viability of the pollen was assessed via colorimetric, in vitro and in vivo assays. The diameter of the pollen grains was determined by measuring the transversal length of the grain. The experimental design was entirely randomized. Studies on pollen ultrastructure were performed via scanning electron microscopy. Pollen viability was high in the colorimetric tests and intermediate in vivo tests; there was no germination in the in vitro tests. The average production for all accessions was 1,253 pollen grains per floral bud. The size of the pollen grains varied from 132 to 163 µm in the wild accessions, and 129 to 146 µm in the cultivated accessions. The pollen grains for all accessions were very large, apolar, spherical as well as inaperturate, with an exine ornamented with pila organized in a Croton pattern. The wild accessions, in general, produced more and larger pollen grains compared with the cultivated accessions.
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ADEDEJI, Olubukola. "Palynology of the Genus Stachytarpheta Vahl. (Verbenaceae)." Notulae Scientia Biologicae 2, no. 4 (2010): 27–33. http://dx.doi.org/10.15835/nsb244816.
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The exine morphology of pollen grains of Stachytarpheta indica (Linn.) Vahl, Stachytarpheta cayennensis (Rich.) Vahl and Stachytarpheta angustifolia (Mill.) Vahl is reported. This study was carried out with a light microscope. Pollen grains from fresh anthers were collected and aceolysed. Statistical analysis used to analyse the data collected include cluster analysis, correlation analysis, similarity and distance indices. The pollen grains are spheroidal to oblate to sub-oblate in shape. They are aperturate, both colpate and porate. Tricolpate types occur most frequently, acolpate, monocolpate, bicolpate and tetracolpate types less frequently. The multicolpate and multiporate attributes in all the species indicate that the genus is not primitive in evolutionary history and this species probably, evolved around in the same time. According to the size, the pollen grains of the genus falls into groups permagna (pollen diameter 100-200 μm) and giganta (pollen diameter greater than 200 μm). S. cayennensis and S. anguistifolia belong to group permagna and S. indica only in the group giganta. This separates S. indica from the other two species. The large pollen grain size in the genus clearly supports the fact that the flowers in the genus are more insect-and-bird pollinated than wind pollinated. The similarity and distance indices of the species showed that S. cayennensis and S. angustifolia are the closest. S. indica is closer to S. angustifolia but farther from S. cayennensis.
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Ivanchenko, Olga, and Valentina Bessonova. "Pollen Quality in Woody Plants in the City Parks of Dnipro, Ukraine." International Letters of Natural Sciences 59 (October 2016): 29–37. http://dx.doi.org/10.18052/www.scipress.com/ilns.59.29.
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This research was conducted to study pollen quality in woody plants in the city parks of Dnipro, which are located at various distances from the sources of anthropogenic pollution. It has been revealed that sterile pollen in its greatest abundance was present in plant species in the Park of Memory and Reconciliation and Molodyozhny park, as both are situated within the range of emission transfer from the Western Industrial Complex, while the least abundant sterile pollen was detected in the park named after Yu. Gagarin and that named after V. Dubinin. According to sterility indices, the pollen inBetula pendulaRoth. and that inAcer platanoidesL. were most sensitive to environmental pollution. In the city parks, the amounts of shrunk and abnormally shaped pollen grains increases; giant forms with grain diameters exceeding standard, as well as dwarf forms are not rare in occurrence. The highest percentage of pollen grains of atypical shape and size was observed in the same parks where the pollen sterility index had its highest values.
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Ismail, Rizgar Y., and Saleem E. Shahbaz. "Use of Pollen Morphology Traits for Identifying Species of Centaurea L. Asteraceae in Kurdistan-Iraq." Science Journal of University of Zakho 8, no. 4 (2020): 131–38. http://dx.doi.org/10.25271/sjuoz.2020.8.4.754.
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The polleniferous material of Centaurea taxa grow in Kurdistan-Iraq was collected. Samples were tested using scanning electron microscopy (SEM) and light microscopy (LM). In the polar view, pollen grain outlines are mostly triangular or triangular-circular. In equatorial view, the elliptic shape is common, while circulars or semicircular shapes are rare. The exine sculpture is scabrate, and the tectum is perforate. Number of sculpture microspinules/ µm², and their heights together with the number of wall perforations provide significant characters for taxa delimitation. Pollen grains of all species are of medium size, very few of some species pollen are larger or smaller in size. Species producing subprolate pollen shape is common, while oblate spheroidal and Prolate spheroidal shapes are less common. The principal component analysis and the discriminant analysis can recognize 65.478% and 87.54% of the total variability respectively; moreover, the discriminant function can correctly classify 125 or 78.125% out of 160 observations for pollen traits.
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Piré, Stella M., and Carmen L. Cristóbal. "EL POLEN DE HELICTERES (STERCULIACEAE) y SU COMPARACIÓN CON GÉNEROS VECINOS." Bonplandia 11, no. 1-4 (2001): 207. http://dx.doi.org/10.30972/bon.111-43945.
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<p>Pollen grains of 41 species representing all seven sections of Helicteres were studied with light and scanning electron microscopy and described. In order to establish palynological affinities Neoregnellia cubensis, Kleinhovia hospita, Reevesia thyrsoidea, Veeresia clarkii, Ungeria floribunda and Pterospermum acerifolium were also examined. Helicteres is palynologically rather uniform with respect to the shape and size of the grains as well as the type and number of the apertures. The pollen grains are usually triporate, oblate or suboblate, amb triangular and medium sized. Nevertheless the exine surface shows great variability. Nine pollen types are recognized on the basis of the sculpture of the exine: Type 1, tectate-perforate, baculate, in sect. Helicteres; Type 11, tectate-perforate, psilate to weakly verrucate, in 4 species of sect. Orthocarpaea; Type 111, tectate-perforate, with the equatorial zone verrucate and the poles psilate, in sect. Stegogamos; Type IV, microreticulate, verrucate, in sect. Polyandria; Type V, tectate, scabrate, verrucate, in sect. Alicteres; Type VI, tectate-perforate, verrucate, in 2 species of sect. Orthocarpaeaand 4 species of sect. Orthothecium; Type VII, tectate-perforatefossulate, verrucate, the verrucae large, irregular in outline, often anastomosed, in 3 species of sect. Orthothecium; Type VIII, tectate to tectate-perforate-fossulate, perforations and fossulae as well as micro-verrugae and micro-echinae densely concentrated at the poles, the equatorial zone psilate or scabrate, in 3 species of sect. Orthothecium; Type IX, tectateperforate- fossulate, microechinate, the perforations and fossulae densely concentrated at the poles, the micro-echinae distributed throughout the surface but hardly differentiated on the poles, in 16 species of sect. Sacarolha and 5 species of sect. Orthothecium. The pollen types are ordered according to the complexity of the exine; with the types with uniform sculpture considered simpler and the types with polar and equatorial zones differentiated considered complex. Keys to identify the nine pollen types of Helicteres and the pollen types of related genera are presented. According to pollen morphology Neoregnellia is closely connected with Helicteres; this genus shares the same pollen type, IX, with sect. Sacarolha and some species of sect. Orthothecium. The pollens of Kleinhovia and Helicteres have many characters in common (shape, size, apertures), the only difference being the microreticulate surface of the former; they are rather close to each other. Reevesia thyrsoidea, Veeresia clarkii and Ungeria floribunda stand apart from Helicteres in having 3-5 brevi-colp(or)ate and suprareticulate grains. The very distinctive pollen of Pterospermum acerifolium (Iarge size, spheroidal, echinate) supports its segregation from the tribe Helictereae. In Helicteres the different patterns of exine sculpture have taxonomic and phylogenetic value. In the first place, they allow the recognition of the 4 monospecific sections (Helicteres, Stegogamos, Alicteres and Polyandria) and at the same time they reveal the coherence of the genus, since the other 3 sections which have many species (Orthocarpaea, Orthothecium and Sacarolha) are connected with each other not only by exomorphological characters but also by pollen characters. In the second place, they provide bases for interpreting infra-generic relationships and the possible origin of the genus.Two possible evolutionary trends of exine sculpture, which are representated in two diagrams, are proposed. The first possibility starts with the Type VI; from this pollen type the evolutionary trend would have diverged in several directions. On one side, a line would lead toward increasing complexity of the exine that would end in Type VIII. This kind of pollen grain would have given rise to Type IX. On the other side, several divergent lines might have taken place; modifications in the exine sculpture would have led toward a progressive simplicity that would culminate in the absence of sculptural elements of Type 11. From this kind of pollen grain Type I might have evolved. The second possibility starts from Type 11; in this case the evolutionary trend of the exine would have gone in only one direction; the exine would have acquired more and more complexity, giving rise to pollen types connected with each other by transitional forms.</p>
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Pacini, Ettore, and Gian Gabriele Franchi. "Pollen biodiversity – why are pollen grains different despite having the same function? A review." Botanical Journal of the Linnean Society 193, no. 2 (2020): 141–64. http://dx.doi.org/10.1093/botlinnean/boaa014.
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Abstract The main morphological, cytological and physiological characters of ripe pollen are described, compared, analysed and discussed individually, in multiple combinations and in respect to the female counterpart and the biotic and abiotic components of the environment. This is to try to understand the reasons why pollen grains have the same reproductive function, but at dispersal are morphologically and physiologically different in many respects. The considered characters are: one or more types of grain per species; shape and size; number of cells; types of pollen dispersal unit; sporoderm stratification, furrows, colpori and other kinds of apertures; pollen presentation and array; water content percentage; and mature pollen reserves and osmotics. Some of the pollen features are correlated between themselves, some with the female counterpart or male and female competition, and others with the different components of the environment where the species lives, when it flowers and when pollen presentation occurs.
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Penny, Rebecca H., and Janet C. Steven. "Sexual dimorphism in pollen grain size in cryptically dioecious Thalictrum macrostylum." Plant Systematics and Evolution 279, no. 1-4 (2009): 11–19. http://dx.doi.org/10.1007/s00606-008-0114-z.
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Cruden, Robert William. "Pollen grain size, stigma depth, and style length: the relationships revisited." Plant Systematics and Evolution 278, no. 3-4 (2009): 223–38. http://dx.doi.org/10.1007/s00606-008-0142-8.
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Cramer, Christopher S. "Laboratory Techniques for Determining Ploidy in Plants." HortTechnology 9, no. 4 (1999): 594–96. http://dx.doi.org/10.21273/horttech.9.4.594.
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Determination of ploidy is an essential plant breeding technique. Laboratory exercises for teaching students how to determine ploidy in plant tissues using various techniques are described for geranium and onion. The different methods include root tip squashes, pollen mother cell squashes, pollen grain size and germinal pore counts, stomata size and density determination, and gross morphology.
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Filho, Roberto Gargione Junqueira, Andréa Beatriz Mendes-Bonato, Maria Suely Pagliarini, Nilton Cesar Pires Bione, Cacilda Borges do Valle, and Maria Isabel de Oliveira Penteado. "Absence of microspore polarity, symmetric divisions and pollen cell fate in Brachiaria decumbens (Gramineae)." Genome 46, no. 1 (2003): 83–88. http://dx.doi.org/10.1139/g02-114.
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Meiotic division and male gametophyte development were analyzed in one tetraploid (2n = 4x = 36) accession of Brachiaria decumbens cv. Basilisk that showed some pollen sterility. Meiotic process was typical of polyploids in that it consisted of multiple chromosome associations. Precocious chromosome migration to the poles, laggards, and micronucleus formation were abundant in both meiosis I and II and resulted in tetrads with micronuclei. After callose dissolution, microspores were released into the anther locule and had the semblance of being normal. Although each microspore initiated its differentiation by pollen mitosis, in 43.24% of the microspores, nuclear polarization was not observed and the typical hemispherical cell plate was not detected. Division was symmetric and microspores lacked differentiation between the vegetative and the generative cell. Both nuclei were of equal size, presented equal chromatin condensation, and had a spherical shape. After the first pollen mitosis and cytokinesis, each cell underwent a new symmetric mitosis without nuclear polarization. At the end of the second pollen mitosis, four equal nuclei were observed in each pollen grain. After the second cytokinesis, the cells gave rise to four equal-sized pollen grains with a similar tetrad configuration that initially remained together. Sterile pollen grains resulted from abnormal pollen mitosis. This anomaly may be explained by a mutation, probably affecting microtubule cytoskeleton formation. The importance of this male-sterile mutation for Brachiaria breeding programs is discussed.Key words: Brachiaria decumbens, male sterility, pollen mitosis, microspore polarity, symmetric division, pollen cell fate, grasses.
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Shen, Huadong, Zhongbo Yu, Ge Yu, and Xiaoli Shi. "Grain Size and Pollen of Sediments in Wanghu Lake (Central China) Linked to Hydro-Environmental Changes." Water 12, no. 1 (2019): 45. http://dx.doi.org/10.3390/w12010045.
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Grain size of lake sediments is often measured in paleolimnological studies, especially investigations of past paleoclimatic and paleohydrologic changes. The implications of such measures, however, remain unclear, since watershed hydrology and the related transfer of materials to the lake are affected by local climate variables, hydrological shifts, and vegetation cover variables. Sediment from Wanghu Lake in the middle reaches of the Yangtze River have apparently been affected by land cover changes and lake-river system transitions caused by a sluice gate built at Fuchi in 1967. These changes influenced the watershed hydrology, thereby confounding paleoclimatic and paleohydrologic interpretations by proxy records in sediment cores. We collected sediment cores from the center of Wanghu Lake and analyzed trends in pollen and physical properties through sedimentary records to investigate land cover changes and hydrological transitions during the past 90 years. The grain size of the sediment core increased with precipitation and the significant relationships between pollen and grain size after 1967 indicated that sediment transfer to the lake was controlled by rainfall and land cover changes due to human-induced deforestation and farming in the lake catchment. Interestingly before 1967, there was no significant relationship between the pollen and grain size or between the precipitation and grain size, indicating that the sediment of WanghuLake was not simply from the lake catchment. The different relationships patterns before and after 1967 indicated that the sediments in the lake were not only transported following precipitation and discharge from the lake catchment but also came from the Yangtze River draining back into the lake during the flood seasons before 1967. These results highlight matters needing attention and the potential application of grain size of sediments for reconstructions of past hydro-environmental changes.
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Horčinová Sedláčková, V., O. Grygorieva, I. Gurnenko, and O. Vergun. "Diversity of Sambucus nigra pollen within Slovakia in selected morphological characters by SEM study." Biosystems Diversity 28, no. 4 (2020): 399–404. http://dx.doi.org/10.15421/012051.
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This study analyzed pollen morphology and characteristics of 20 Sambucus nigra L. genotypes from populations of various ecotypes and geographical localities from the territory of Slovakia. We used principal component analysis to explore variability in pollen grain size (polar and equatorial diameter), shape, aperture type, and exine ornamentation by scanning electron microscopy. The combination of these morphological characteristics and ultrastructure allows us to determine the differences or similarities between the same and various species and genotypes, which may be a useful tool for systematics with significant diagnostic value. The findings confirmed small differences among the genotypes in measured traits with polar and equatorial diameters in the range from 22.30 to 26.64 μm and from 12.81 to 14.45 μm, respectively. Shape index (P/E ratio) depending on elongation or roundness of pollen grains varied from 1.66 to 2.02. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) of morphological data helped to compare evaluated morphometric parameters and identified three closely related groups. It was noted that the diversity of surface sculpturing of pollen grains in combination with their shape and size enables us to use a complex of fine morphologic signs for S. nigra pollen identification. Pollen data combined with other morphological evidence (e.g., floral characters) have more recently become an important indicator of which genotypes may be the best representatives of species.
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Śnieżko, Renata. "Pollen tube branching in the ovary of five species of Oenothera." Acta Societatis Botanicorum Poloniae 65, no. 1-2 (2014): 111–16. http://dx.doi.org/10.5586/asbp.1996.019.
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Flowers of <em>Oenothera hookeri</em> Torr. et Gray, <em>Oe. brevistylis</em> and <em>Oe. lamarkiana</em> de Vries were pollinated after anthesis by insects. <em>Oe. biennis</em> L., <em>Oe. suaveolens</em> Desf and sulfurea were selfpollinated in the buds. Pollen morphology was slightly different: <em>Oe. hookeri</em> have regular, triporated pollen, often germinating through two pores; in <em>Oe. suaveolens</em> many pollen grains had callose patches on the intine; in <em>Oe. brevistylis</em> tetraporated pollen were more often than in other species; in <em>Oe. lamarckiana</em> many pollen grains were empty; in <em>Oe. biennis</em> and <em>Oe. suaveolens</em> pollen grain size and viability varied. The pollen tube growth and fertilization were similar in 5 species and can be considered as typical for <em>Oenothera</em>. In the ovary pollen tubes branched and changed their growth direction. Near micropyle they formed short branches to the inner integument. In the nucellus the pollen tube became swollen.
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Lamborn, Ellen, James E. Cresswell, and Mark R. Macnair. "The potential for adaptive evolution of pollen grain size in Mimulus guttatus." New Phytologist 167, no. 1 (2005): 289–96. http://dx.doi.org/10.1111/j.1469-8137.2005.01403.x.
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Struwig, M., S. J. Siebert, and A. Jordaan. "Pollen morphology of members of southern African Boerhavia and Commicarpus (Nyctaginaceae)." Bothalia 43, no. 1 (2013): 15–22. http://dx.doi.org/10.4102/abc.v43i1.82.
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In southern Africa, Boerhavia L. and Commicarpus Standl. are the most species-rich genera of the Nyctaginaceae. Hitherto, the pollen morphology of only three southern African species of each of these genera has been described. A palynological study of the remaining species is therefore necessary to complete the information for the taxa. The pollen morphology of sixteen species was studied with light, scanning electron and transmission electron microscopy. Pollen grains of Boerhavia and Commicarpus are uniform in shape and sculpturing. Grains are spheroidal and pantoporate, and the tectum tubuliferous and spinulose. Pollen grains of the Boerhavia are 52–91 μm in diameter and those of Commicarpus 52–129 μm. Spinules in both genera are 1–5 μm long. Pore plates have one or two spinules. In both genera the exine is 3.5–11.5 μm thick, the tectum 0.9–3.9 μm thick and the collumellae 0.6–2.8 μm long. Foot layers are 0.9–5.1 μm thick and the endexine is barely visible. Size variation of the pollen grain, pore diameter and exine thickness overlap and cannot be used to distinguish between the two genera or the individual species.
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Hebda, R. J., C. C. Chinnappa, and B. M. Smith. "Pollen morphology of the Rosaceae of western Canada. IV. Luetkea, Oemleria, Physocarpus, Prunus." Canadian Journal of Botany 69, no. 12 (1991): 2583–96. http://dx.doi.org/10.1139/b91-322.
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Pollen grains of 12 species of western Canadian rosaceous genera, Luetkea, Oemleria, Physocarpus, and Prunus, were studied in the light microscope and scanning electron microscope. All pollen grains are produced as isopolar, radially symmetrical, usually tricolporate monads. Grains are predominantly spheroidal with a circular to triangular amb. Most of the species exhibit a well-developed chambered aperture complex at the equator, formed by a pair of sexinal flaps whereas in Prunus spinosa, Prunus americana, and Prunus virginiana the chamber is absent or weakly developed. Oemleria cerasiformis has no pore flaps. Apertures of Prunus emarginata and Prunus virginiana often have an equatorial bridge over the aperture complex. The exine of Prunus, Physocarpus, and Luetkea pollen is tectate perforate, like that of many Rosaceae. Sculpturing consists of ridges and valleys that form a striate to rugulate pattern. Ridges and valleys tend to be mainly parallel to the colpus but often loop near the poles. Pollen grains of Prunus spinosa are always rugulate or vermiculate with ridges arranged randomly. Oemleria cerasiformis pollen appears tectate imperforate. Ridges and valleys intersect at triple points in the subpolar region and curve in a semicircle around the pore area. On this basis Oemleria pollen is distinct from all other western Canadian Rosaceae. Pollen grain size ranges from small for Luetkea pectinata (17 μm in diameter) to medium for Prunus spinosa (36 × 33 μm). Key words: pollen morphology, Rosaceae, Western Canada, systematics.
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Avdieienko, Yuliia. "On methodology of palaeogeographical studies of karst cave deposits of Ukraine." Physical Geography and Geomorphology 103-104, no. 5-6 (2020): 50–56. http://dx.doi.org/10.17721/phgg.2020.5-6.06.
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New approaches developed within the complex palaeogeographic methodology of cave deposits studies for reconstruction of the past ecological conditions are presented in the paper. The relevance and reliability of results of such studies are shown on the cases from the previous research of cave systems in Ukraine. The methodology based of palynological and lithological (including grain-size analysis) study of terrigenous cave deposits is proposed, and the advantages of their complex application within the multidisciplinary palaeoenvironmental study are proved. The reliability of palaeovegetational reconstructions based on pollen studies of clastic cave deposits is confirmed by the compatibility of their results with those obtained from coeval subaerial deposits. The same patterns were shown by a comparison of pollen from hyaena coprolites in the cave and their enclosing sediments. It has been found that the content of redeposited pollen in the clastic sediments of caves depends on their particle size distribution, sharply increasing in sandy deposits. The grain-size composition of cave deposits also provides information on the genesis of deposits and, thus, indirectly, on paleoenvironmental conditions. Changes in clay, large silt and sand fractions are of main importance for the interpretation of the results. A direct correlation of paleoclimatic signals obtained by the results of pollen and lithological analyses with the indicators of magnetic susceptibility has been established. The use of these paleogeographic methods for studying cave deposits, namely pollen analyses, lithological (in particular, grain-size), palaeontological, petromagnetic, palaeogenetic, radiocarbon and paleomagnetic methods, will be able to control the reliability of the reconstruction by collate them. Multidisciplinary study of the cave deposits has a great potential for reconstructions of the ancient Man environments as deposits of many caves include archaeological horizons of different material cultures from the Early Palaeolithic to the Early Iron Age.
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Alabdullah, Abdul Kader, Graham Moore, and Azahara C. Martín. "A Duplicated Copy of the Meiotic Gene ZIP4 Preserves up to 50% Pollen Viability and Grain Number in Polyploid Wheat." Biology 10, no. 4 (2021): 290. http://dx.doi.org/10.3390/biology10040290.
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Although most flowering plants are polyploid, little is known of how the meiotic process evolves after polyploidisation to stabilise and preserve fertility. On wheat polyploidisation, the major meiotic gene ZIP4 on chromosome 3B duplicated onto 5B and diverged (TaZIP4-B2). TaZIP4-B2 was recently shown to promote homologous pairing, synapsis and crossover, and suppress homoeologous crossover. We therefore suspected that these meiotic stabilising effects could be important for preserving wheat fertility. A CRISPR Tazip4-B2 mutant was exploited to assess the contribution of the 5B duplicated ZIP4 copy in maintaining pollen viability and grain setting. Analysis demonstrated abnormalities in 56% of meiocytes in the Tazip4-B2 mutant, with micronuclei in 50% of tetrads, reduced size in 48% of pollen grains and a near 50% reduction in grain number. Further studies showed that most of the reduced grain number occurred when Tazip4-B2 mutant plants were pollinated with the less viable Tazip4-B2 mutant pollen rather than with wild type pollen, suggesting that the stabilising effect of TaZIP4-B2 on meiosis has a greater consequence in subsequent male, rather than female gametogenesis. These studies reveal the extraordinary value of the wheat chromosome 5B TaZIP4-B2 duplication to agriculture and human nutrition. Future studies should further investigate the role of TaZIP4-B2 on female fertility and assess whether different TaZIP4-B2 alleles exhibit variable effects on meiotic stabilisation and/or resistance to temperature change.
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LAU, T. C., X. LU, R. T. KOIDE, and A. G. STEPHENSON. "Effects of soil fertility and mycorrhizal infection on pollen production and pollen grain size of Cucurbita pepo (Cucurbitaceae)." Plant, Cell and Environment 18, no. 2 (1995): 169–77. http://dx.doi.org/10.1111/j.1365-3040.1995.tb00350.x.
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Jürgens, Andreas, Taina Witt, and Gerhard Gottsberger. "Pollen grain size variation in Caryophylloideae: a mixed strategy for pollen deposition along styles with long stigmatic areas?" Plant Systematics and Evolution 298, no. 1 (2011): 9–24. http://dx.doi.org/10.1007/s00606-011-0518-z.
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Montes-R, Consuelo, and Jeffrey W. White. "Effect of selection for pollen grain size on various traits in common bean." Euphytica 90, no. 1 (1996): 59–63. http://dx.doi.org/10.1007/bf00025160.
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