A sophisticated case of division of labour in the trimorphic stamens of the Cassia fistula (Leguminosae) flower

Abstract Buzz-pollinated pollen flowers have pollen as the primary resource for pollinators and must deal with a conflict between the exploitation of pollen grains by bees and pollination success. It has been hypothesized that heterostemony allows division of labour between stamens as a solution to the pollen dilemma. To test the division of labour hypothesis, we chose Cassia fistula, which has a trimorphic androecium and analysed androecium development, pollen grain release mechanisms and visitor behaviour. We explored the reflectance of floral organs and carried out an exclusion experiment to test the attractiveness of each stamen morph to the bee species. Finally, we explored the structural, ultrastructural and functional variation between the pollen grains, including pollen viability across stamen morphs. The differences among the three stamen morphs, which is developed from two whorls of the stamen, are the first evidence of the division of labour in our study system. Large Bombus and Xylocopa bees actively and exclusively exploited the pollen grains from the central poricidal anthers generating pollen deposition on their bodies. The reflectance pattern of floral organs indicated a targeting of these large bees to the central anthers, corroborated by the anther manipulative experiment where only the exclusion of the anthers positioned in the flower centre, especially the intermediate stamens, reduced bee visits. Both results revealed a division of labour, in which the intermediate stamen morph was responsible for both floral attractiveness and pollen resources. Only the largest stamen morph produced germinable pollen grains, highlighting their role as pollinating stamens. The smallest stamen morph has a less clear function, likely representing an economy in pollen production for feeding function. Our findings suggest that the evolution of the trimorphic androecium is associated with division of labour in large pollen flowers and can represent a strong strategy for circumventing the pollen dilemma, optimizing the feeding function by reducing pollen grain investment from central anthers.

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Abnormal Microspore Development Leads to Pollen Abortion in a Seedless Mutant of ‘Ougan’ Mandarin (Citrus suavissima Hort. ex Tanaka)

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.132.6.777 ◽

2007 ◽

Vol 132 (6) ◽

pp. 777-782 ◽

Cited By ~ 22

Author(s):

Zhiyong Hu ◽

Min Zhang ◽

Qigen Wen ◽

Jie Wei ◽

Hualin Yi ◽

...

Keyword(s):

Pollen Viability ◽

Pollen Grains ◽

Pollen Grain ◽

Mature Pollen ◽

Abnormal Development ◽

Microspore Development ◽

Wild Type ◽

Pollen Abortion ◽

Tetrad Stage ◽

In The Wild

Seedlessness is of commercial importance in citrus (Citrus L.). Seedless ‘Ougan’ mandarin (C. suavissima) was selected from a bud sport mutation that occurred in ‘Ougan’ mandarin. We analyzed their pollen viability through KI-I2 and FDA staining, and examined the anthers of wild-type (seedy) and seedless mutant ‘Ougan’ mandarin using histological and cytochemical methods to characterize the process of pollen development. No pollen fertility was detected in this mutant. Pollen abortion in anthers of the mutant occurred at the tetrad stage of microspore development, and almost all the tetrads were abnormal. The mutant had heterogeneous microspore populations, including monads, dyads, triads, tetrads, and polyads in the same microsporangium. Pollen grain number per anther of the mutant was 21.9% less than the wild type. Morphology of mature pollen grains using SEM showed that the shape of mature pollen grains from both wild type and mutant is similar, but the microsporangia of the latter contained pollen grains of more variable sizes. At the early mature pollen grain stage, abundant starch grains and lipids appeared in the wild type's pollen, but fewer amounts were observed in the mutant. Moreover, the tapetal cells of the wild type accumulated lipids, but not those of the mutant. Results indicated that the abnormal development of the microspore led to pollen abortion in the mutant, and this could be the reason for its seedlessness. However, the genetic reasons for the aberrant tetrads are not clear and are under investigation.

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Differences in stomatal and pollen grain dimensions and pollen viability between Paspalum rawitscheri populations

Ciência e Natura ◽

10.5902/2179460x40749 ◽

2020 ◽

Vol 42 ◽

pp. e46

Author(s):

Jéssica Mena Barreto De Freitas ◽

Andrielle Wouters Kuhn ◽

Viviane Dal-Souto Frescura ◽

Liliana Essi ◽

Solange Bosio Tedesco

Keyword(s):

Grain Size ◽

Pollen Viability ◽

Pollen Grains ◽

Pollen Grain ◽

Low Fertility ◽

Leaf Epidermis ◽

Stomatal Size ◽

Pollen Grain Size ◽

Different Populations ◽

Santa Maria

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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Floral herbivory does not reduce pollination-mediated fitness in shelter rewarding Royal Irises

10.1101/184382 ◽

2017 ◽

Cited By ~ 1

Author(s):

Mahua Ghara ◽

Christina Ewerhardy ◽

Gil Yardeni ◽

Mor Matzliach ◽

Yuval Sapir

Keyword(s):

Fruit Set ◽

Seed Set ◽

Pollen Grains ◽

Reproductive Organs ◽

Pollen Grain ◽

Lower Number ◽

Pollen Deposition ◽

Pollination Services ◽

Pollinator Visitation ◽

Direct Damage

ABSTRACTFlorivory, the damage to flowers by herbivores can affect fitness both directly and indirectly. Flowers consumed by florivores may fail to produce fruit or produce lower seed set because of direct damage to reproductive organs. In addition, eaten flowers are less attractive to pollinators because of reduced or modified advertisement, which reduces pollination services. While observational data are abundant, experimental evidence is scarce and results are contrasting. We tested experimentally the effect of florivory on both pollinator visitation and reproductive success in three species of the Royal Irises, which have large flowers that are attractive to pollinators, and potentially also for florivores. We hypothesized that florivory will reduce pollen deposition due to reduced attractiveness to pollinators, while fruit set and seed set will depend on the extent of florivory. We performed artificial florivory in two experiments over two years. In the first experiment, each of the three floral units of a single Iris flower was subject to either low or high artificial florivory, or left un-touched as control. We counted the number of pollen grains deposited on each of the three stigmas as a measure of pollinator visitation. In the second experiment, three flowers of the same plant received low, high, or no artificial florivory and were further recorded for fruit and seed production. In 2016, high artificial florivory revealed lower number of pollen grains on stigmas of Iris atropurpurea, but in 2017 there was no difference. Similarly, number of pollen grains in high artificial was lower than low florivory in 2017 in I. petrana. No significant effect of florivory was found on pollen grain deposition, fruit set or seed set. The results remained consistent across species and across years. The results undermine the assumption that flower herbivory is necessarily antagonistic interaction and suggests that florivores may not be strong selection agents on floral reproductive biology in the Oncocyclus irises.

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Pollen grain traits of oil species from the Novi Sad collection

Genetika ◽

10.2298/gensr0903263a ◽

2009 ◽

Vol 41 (3) ◽

pp. 263-270 ◽

Cited By ~ 3

Author(s):

Jovanka Atlagic ◽

Ana Marjanovic-Jeromela ◽

Radovan Marinkovic ◽

Sreten Terzic

Keyword(s):

Staining Method ◽

Pollen Viability ◽

Pollen Grains ◽

Grain Morphology ◽

Pollen Grain ◽

Viable Pollen ◽

Continuous Work ◽

Novi Sad ◽

Pollen Grain Morphology ◽

Specific Number

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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Electrostatic Processes Underlying Natural and Mechanized Transfer of Pollen

10.32747/1998.7613035.bard ◽

1998 ◽

Author(s):

Edward Law ◽

Samuel Gan-Mor ◽

Hazel Wetzstein ◽

Dan Eisikowitch

Keyword(s):

Electric Fields ◽

Pollen Viability ◽

Pollen Grains ◽

Basic Knowledge ◽

Pollen Deposition ◽

Average Charge ◽

Pollen Transfer ◽

Transfer Vectors ◽

Pollination Systems ◽

Relaxation Characteristics

The project objective was to more fully understand how the motion of pollen grains may be controlled by electrostatic forces, and to develop a reliable mechanized pollination system based upon sound electrostatic and aerodynamic principles. Theoretical and experimental analyses and computer simulation methods which investigated electrostatic aspects of natural pollen transfer by insects found that: a) actively flying honeybees accumulate ~ 23 pC average charge (93 pC max.) which elevates their bodies to ~ 47 V likely by triboelectrification, inducing ~ 10 fC of opposite charge onto nearby pollen grains, and overcoming their typically 0.3-3.9 nN detachment force resulting in non-contact electrostatic pollen transfer across a 5 mm or greater air gap from anther-to-bee, thus providing a theoretical basis for earlier experimental observations and "buzz pollination" events; b) charge-relaxation characteristics measured for flower structural components (viz., 3 ns and 25 ns time constants, respectively, for the stigma-style vs. waxy petal surfaces) ensure them to be electrically appropriate targets for electrodeposition of charged pollen grains but not differing sufficiently to facilitate electrodynamic focusing onto the stigma; c) conventional electrostatic focusing beneficially concentrates pollen-deposition electric fields onto the pistill tip by 3-fold as compared to that onto underlying flower structures; and d) pollen viability is adequately maintained following exposure to particulate charging/management fields exceeding 2 MV/m. Laboratory- and field-scale processes/prototype machines for electrostatic application of pollen were successfully developed to dispense pollen in both a dry-powder phase and in a liquid-carried phase utilizing corona, triboelectric, and induction particulate-charging methods; pollen-charge levels attained (~ 1-10 mC/kg) provide pollen-deposition forces 10-, 77-, and 100-fold greater than gravity, respectively, for such charged pollen grains subjected to a 1 kV/cm electric field. Lab and field evaluations have documented charged vs. ukncharged pollen deposition to be significantly (a = 0.01-0.05) increased by 3.9-5.6 times. Orchard trials showed initial fruit set on branches individually treated with electrostatically applied pollen to typically increase up to ~ 2-fold vs. uncharged pollen applications; however, whole-tree applications have not significantly shown similar levels of benefit and corrective measures continue. Project results thus contribute important basic knowledge and applied electrostatics technology which will provide agriculture with alternative/supplemental mechanized pollination systems as tranditional pollen-transfer vectors are further endangered by natural and man-fade factors.

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In vitro germination and viability of pea pollen grains after application of organic nano-fertilizers

Pesticidi i fitomedicina ◽

10.2298/pif1701061g ◽

2017 ◽

Vol 32 (1) ◽

pp. 61-65 ◽

Cited By ~ 1

Author(s):

Natalia Georgieva ◽

Ivelina Nikolova ◽

Valentin Kosev ◽

Yordanka Naydenova

Keyword(s):

Pollen Tube ◽

Pollen Germination ◽

Culture Media ◽

Pollen Viability ◽

Pollen Grains ◽

Pollen Grain ◽

In Vitro Germination ◽

Pisum Sativum L ◽

Pollen Tube Elongation

The objective of this study was to evaluate the influence of two organic nanofertilizers, Lithovit and Nagro, on in vitro germination, pollen tube elongation and pollen grain viability of Pisum sativum L cv. Pleven 4. The effect of their application was high and exceeded data for the untreated control (44.2 and 47.23 % regarding pollen germination and pollen tube elongation, respectively), as well as the effect of the control organic algal fertilizer Biofa (17.5 and 27.9 %, respectively). Pollen grains were inoculated in four culture media. A medium containing 15% sucrose and 1% agar had the most stimulating impact on pea pollen grains. Pollen viability, evaluated by staining with 1% carmine, was within limits of 74.72-87.97%. The highest viability of pollen grains was demonstrated after the application of Nagro organic nano-fertlizer.

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Quantitative methods in microscopy to assess pollen viability in different plant taxa

Plant Reproduction ◽

10.1007/s00497-020-00398-6 ◽

2020 ◽

Vol 33 (3-4) ◽

pp. 205-219

Author(s):

Lorenzo Ascari ◽

Cristina Novara ◽

Virginia Dusio ◽

Ludovica Oddi ◽

Consolata Siniscalco

Keyword(s):

Statistical Power ◽

Quantitative Methods ◽

Pollen Viability ◽

Crop Improvement ◽

Pollen Grains ◽

Pollen Sterility ◽

Pollen Grain ◽

Automated Image Analysis ◽

Future Research ◽

Sterile Pollen

AbstractHigh-quality pollen is a prerequisite for plant reproductive success. Pollen viability and sterility can be routinely assessed using common stains and manual microscope examination, but with low overall statistical power. Current automated methods are primarily directed towards the analysis of pollen sterility, and high throughput solutions for both pollen viability and sterility evaluation are needed that will be consistent with emerging biotechnological strategies for crop improvement. Our goal is to refine established labelling procedures for pollen, based on the combination of fluorescein (FDA) and propidium iodide (PI), and to develop automated solutions for accurately assessing pollen grain images and classifying them for quality. We used open-source software programs (CellProfiler, CellProfiler Analyst, Fiji and R) for analysis of images collected from 10 pollen taxa labelled using FDA/PI. After correcting for image background noise, pollen grain images were examined for quality employing thresholding and segmentation. Supervised and unsupervised classification of per-object features was employed for the identification of viable, dead and sterile pollen. The combination of FDA and PI dyes was able to differentiate between viable, dead and sterile pollen in all the analysed taxa. Automated image analysis and classification significantly increased the statistical power of the pollen viability assay, identifying more than 75,000 pollen grains with high accuracy (R2 = 0.99) when compared to classical manual counting. Overall, we provide a comprehensive set of methodologies as baseline for the automated assessment of pollen viability using fluorescence microscopy, which can be combined with manual and mechanized imaging systems in fundamental and applied research on plant biology. We also supply the complete set of pollen images (the FDA/PI pollen dataset) to the scientific community for future research.

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Pollen Grain and Hybridization Studies in the Genus Capsicum

Notulae Scientia Biologicae ◽

10.15835/nsb819767 ◽

2016 ◽

Vol 8 (1) ◽

pp. 134-138 ◽

Cited By ~ 1

Author(s):

Tomi Lois OLATUNJI ◽

Joseph Akintade MORAKINYO

Keyword(s):

Success Rate ◽

Pollen Viability ◽

Pollen Grains ◽

Pollen Grain ◽

Interspecific Crosses ◽

Putative Hybrid ◽

Gene Exchange ◽

Viable Pollen ◽

Pollination Success ◽

Capsicum Species

The current study aimed to evaluate the pollen viability of the commonly cultivated varieties of Capsicum species and assessed the potentials for gene exchange among the genotypes through hybridization studies. Capsicum annuum var. abbreviatum, C. annuum var. acuminatum, C. annuum var. grossum and C. frutescens var. baccatum were the species and varieties used in this study. The present findings indicated that the percentage of pollen viability varied in the studied Capsicum genotypes. The highest pollen viability was obtained in C. annuum var. abbreviatum (96.3%), followed by C. annuum var. grossum (95%), and C. annuum var. acuminatum (91.1%). The lowest pollen viability was recorded in C. frutescens var. baccatum (86.2%). The pollen viability was high in most varieties indicating that meiosis is normal, resulting in viable pollen grains. Several intraspecific and interspecific crosses were performed among the Capsicum genotypes and three putative hybrid fruits were produced. Percentage successes obtained in the crosses were low and comparable in both intra and inter-specific crosses. In the entire crosses pattern, pollination success of 10% was recorded for C. frutescens var. baccatum and C. annuum var. acuminatum. Knowing the nature and viability of pollen grains may help in predicting the success rate of hybridization and the successful crosses between C. frutescens var. baccatum and C. annuum var. acuminatum suggest that these two varieties are the closest genetically.

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Evaluation of Pollen Quality and Self-Fertility in Selected Cultivars of Asian and European Pears

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha45210877 ◽

2017 ◽

Vol 45 (2) ◽

pp. 375-382 ◽

Cited By ~ 2

Author(s):

Monika BIENIASZ ◽

Tomas NECAS ◽

Ewa DZIEDZIC ◽

Ivo ONDRASEK ◽

Bożena PAWŁOWSKA

Keyword(s):

Pollen Germination ◽

Pollen Viability ◽

Pollen Grains ◽

Pollen Grain ◽

Germination Index ◽

Open Pollination ◽

Asian Pear ◽

Pollen Donor ◽

Pear Orchard ◽

Cultivation History

Asian pears have become increasingly popular in the European market, but their cultivation history in Europe is rather short. Pear is a demanding species in terms of pollen – donor cultivar. The self-fertility phenomenon in Asian pear cultivars is not currently known. The study was conducted in a 6-year pear orchard (of 23 Asian and 5 European cultivars) at the Mendel University in Lednice (Czech Republic). The following traits were assessed: number of pollen grains, pollen viability, pollen grain germination, self-fertility and the pollen germination index (PGI). European cultivar – ‘Clapp’s Favourite’ and Asian cultivars – ‘Zao Su Li’, and ‘Shinko’ were characterized by the highest number of pollen grains (over 50,000 grains). Asian cultivar ‘Dangshansu Li’ had the lowest number of pollen grains (less than 10,000 grains). The pollen viability of Asian pears ranged between 90 and 100%. Among European pears, ‘Williams Bon Chrétien’ and ‘Clapp’s Favourite’ exhibited the highest pollen viability (90%), while the lowest viability was observed for the pollen of cultivars ‘Beurré Bosc’ and ‘Alexander Lucas’ pear (60-70%). Additionally, it was found that the germination capacity of the latter two cultivars was very weak (40-70%). After open– pollination all investigated cultivars exhibited greater pollen germination index (PGI) comparing to self-pollination. After the cross-pollination the percentage of pollen tubes below the 20% value at half the length of the pistil suggested a strong incompatibility between the crossed cultivars. The results clearly showed that none of the Asian cultivars are self-fertile, and they require a pollen – donor to produce fruits.

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Effects of Ni2+ and Cu2+ on K+ and H+ currents in lily pollen protoplasts

Functional Plant Biology ◽

10.1071/fp17033 ◽

2017 ◽

Vol 44 (12) ◽

pp. 1171

Author(s):

Maria Breygina ◽

Denis V. Abramochkin ◽

Nikita Maksimov ◽

Igor Yermakov

Keyword(s):

Heavy Metals ◽

Membrane Potential ◽

Pollen Viability ◽

Control Level ◽

Pollen Grains ◽

Pollution Assessment ◽

Term Treatment ◽

Pollen Grain ◽

Patch Clamp Technique ◽

Short Term Treatment

Heavy metals affect plant development and reproduction if they are present in excessive amounts, a situation that is becoming increasingly common. Pollen is a convenient object for pollution assessment as it is in most cases a 2- or 3-cellular organism exposed to the environment. At the same time, pollen is a key stage in the life cycle of seed plants; pollen viability and efficiency of germination are crucial for reproductive success and crop yield. In the present study we reveal for the first time, to our knowledge, targets for heavy metals (Cu2+ and Ni2+) in the pollen grain plasma membrane using the patch-clamp technique. Ni2+ dramatically decreases K+ current in pollen grain protoplasts, whereas Cu2+ does not alter the current density. Instead, Cu2+ strongly enhances H+ current driven by H+-ATPase, whereas Ni2+ fails to affect this current. The short-term treatment with Cu2+ also leads to reactive oxygen species (ROS) accumulation in pollen grain protoplasts but intracellular pH and membrane potential remain unchanged. Ni2+ had no significant effect on ROS content or membrane potential. Thus, plasmalemma K+ channels in pollen grains are sensitive to Ni2+ and H+-ATPase is sensitive to Cu2+, possibly, in a ROS-mediated way. Both metals leave pollen viable since membrane potential is maintained at the control level.

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