Pollen biodiversity – why are pollen grains different despite having the same function? A review

2020 ◽  
Vol 193 (2) ◽  
pp. 141-164 ◽  
Author(s):  
Ettore Pacini ◽  
Gian Gabriele Franchi
Keyword(s):  
Pollen Dispersal ◽  
Pollen Grains ◽  
Reproductive Function ◽  
Female Competition ◽  
Size Number ◽  
Pollen Presentation ◽  
Dispersal Unit ◽  
Number Of Cells ◽  
Physiological Characters ◽  
Female Counterpart

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.

scholarly journals Pollination ecology of Clerodendrum indicum (Lamiaceae): first report of deceit pollination by anther-mimicking stigma in a bisexual flower

2017 ◽  
Vol 65 (3) ◽  
pp. 988
Author(s):  
Arijit Ghosh ◽  
Pankaj K. Pal
Keyword(s):  
Visual Cues ◽  
Pollen Dispersal ◽  
Pollen Grains ◽  
Pollination Ecology ◽  
The Body ◽  
Pollen Transfer ◽  
Bisexual Flower ◽  
Flower Opening ◽  
Pollen Presentation ◽  
Deceit Pollination

Clerodendrum indicum (Lamiaceae) is a medicinally important shrub. We have studied the details of its pollination ecology which was hitherto unknown. The work was done during three consecutive years 2012-2014, based on 118 plants occurring in three widely separated wild populations in West Bengal, India, together with 25 individuals grown in an experimental plot. Details of flower structure and dynamics of floral events, pollen production and pollen dispersal, visitors and pollinators, floral attractants and floral rewards and pollen transfer mechanism have been worked out by standard methodologies with a 10x high resolution hand lens (IRL), a Leica WILD M3B Stereo-binocular microscope (Switzerland) and a Leica DMLB compound bright field light microscope (Germany). The tubular flower of four-day longevity attracts its visitors by visual cues. Flowers are visited regularly by ten species of insects. On the basis of the visitor behaviour, these can be classified into three distinct categories, viz., visitors belonging to Category-I act on cushion and trichome nectaries of calyx and corolla respectively, those of Category-II act on the dehisced anthers and trichome nectaries of corolla while those of Category-III act on dehisced anthers as well as receptive stigma. Majority of the visitors belong to either Category-I or Category-II. They visit only the 2nd day flowers and never visit a 3rd day flower when the stigma assumes receptivity. Therefore, they are not regarded as pollinators but, act as pollen and/or nectar robbers. Those are discriminated by offering secretions from extra-nuptial nectaries of the flower. Visitor species of Category-III, represented by a species of Trigona, constitute the legitimate pollinator of the plant and thereby, making the plant monophilic. Pollen presentation from the bisexual, dichogamous and protandrous flower takes place on the 2nd day, while the stigma assumes its receptivity on the 3rd day of flower opening. Pollen transfer to the body of the pollinator by a 2nd day flower in its male phase is achieved by offering edible pollen grains. On the other hand, a 3rd day flower at its female phase is devoid of the reward (pollen grain). The yellow shiny receptive stigma of such a flower strikingly mimics the freshly dehisced anthers and the pollinators being lured by such a stigma inadvertently transfer pollen onto it. C. indicum is so far the only known species of flowering plants where deceit pollination occurs by anther-mimicking stigma in a bisexual flower.

scholarly journals Accelerated diversification correlated with functional traits shapes extant diversity of the early divergent angiosperm family Annonaceae

2019 ◽  
Author(s):  
B. Xue ◽  
X. Guo ◽  
J.B. Landis ◽  
M. Sun ◽  
C.C. Tang ◽  
...  
Keyword(s):  
Species Richness ◽  
Method Of Moments ◽  
Pollen Dispersal ◽  
Sex Expression ◽  
Diversification Rates ◽  
Total Species Richness ◽  
Dispersal Unit ◽  
High Species Richness ◽  
Selected Traits ◽  
Method Of Moments Estimator

BackgroundA major goal of phylogenetic systematics is to understand both the patterns of diversification and the processes by which these patterns are formed. Few studies have focused on the ancient, species-rich Magnoliales clade and its diversification pattern. Within Magnoliales, the pantropically distributed Annonaceae are by far the most genus-rich and species-rich family-level clade, with c. 110 genera and c. 2,400 species. We investigated the diversification patterns across Annonaceae and identified traits that show varied associations with diversification rates using a time-calibrated phylogeny of 835 species (34.6% sampling) and 11,211 aligned bases from eight regions of the plastid genome (rbcL, matK, ndhF, psbA-trnH, trnL-F, atpB-rbcL, trnS-G, and ycf1). Two hypotheses that might explain patterns of diversification—the ‘museum model’ and heterogeneous diversification rates—are also evaluated.ResultsTwelve rate shifts were identified using BAMM: in Annona, Artabotrys, Asimina, Drepananthus, Duguetia, Goniothalamus, Guatteria, Uvaria, Xylopia, the tribes Miliuseae and Malmeeae, and the Desmos-Dasymaschalon-Friesodielsia-Monanthotaxis clade (which collectively account for over 80% of the total species richness in the family). TurboMEDUSA and method-of-moments estimator analyses showed largely congruent results. A positive relationship between species richness and diversification rate is revealed using PGLS. We further explore the possible role of selected traits (habit, pollinator trapping, floral sex expression, pollen dispersal unit, anther septation, and seed dispersal unit) in shaping diversification patterns, based on inferences of BiSSE, MuSSE, HiSSE, and FiSSE analyses. Our results suggest that the liana habit, the presence of circadian pollinator trapping, androdioecy, and the dispersal of seeds as single-seeded monocarp fragments are closely correlated with higher diversification rates; pollen aggregation and anther septation, in contrast, are associated with lower diversification rates.ConclusionOur results show that the high species richness in Annonaceae is likely the result of recent increased diversification rather than the steady accumulation of species via the ‘museum model’. BAMM, turboMEDUSA, and the method-of-moments estimator all indicate heterogeneity in diversification rates across the phylogeny, with different traits associated with shifts in diversification rates in different Annonaceae clades.

scholarly journals Morphology of Anemone sylvestris L. flower (Ranunculaceae)

2016 ◽  
Vol 75 (1) ◽  
pp. 74-80 ◽  
Author(s):  
Bożena Denisow ◽  
Sebastian Antoń ◽  
Małgorzata Wrzesień
Keyword(s):  
Seed Set ◽  
Pollen Dispersal ◽  
Pollen Grains ◽  
Starch Accumulation ◽  
Pollination Syndrome ◽  
Wind Pollination ◽  
Intermediate Form ◽  
Protected Species ◽  
Large Size ◽  
Opening And Closing

Abstract During the monitoring of populations of Anemone sylvestris L. (Ranunculaceae), a protected species in Poland, we found that the seed set is impaired. The flower is considered an adaptation that has coevolved to achieve effective pollination and successful fertilization. Therefore we have focused on the morphological and anatomical characteristics of the flowers of A. sylvestris L. as a prelude to the study of the species’ pollination biology and plant breeding system. The large size of the flower (50.6 ± 16.4 mm in dimensions) and its bowl shape fulfil both the biotic pollination syndrome and the aerodynamic requirements for pollen dispersal and capture. The opening and closing of the perianth provide a shelter for beetles. The odourless perianth, absence of nectar, scarcity of pollen (approximately 200 000 pollen grains per flower) and its traits - small size (axis P = 18.52 ± 1.0 μm; E = 16.59 ± 0.9 μm), lack of balsam on the exine surface, starch accumulation in more than 95% of pollen grains correspond to the specialization in anemophily. The stigma is papillous, the dense hairs are situated between single carpels indicating adaptation to capturing dry pollen and specialization in the wind pollination syndrome. The flower of A. sylvestris is an example for an intermediate form between entomophily and anemophily, i.e. a secondary and more advanced feature among Ranunculaceae.

Pollen dispersal and gene flow by pollen in Araucaria angustifolia

2003 ◽  
Vol 51 (3) ◽  
pp. 309 ◽  
Author(s):  
V. A. Sousa ◽  
H. H. Hattemer
Keyword(s):  
Gene Flow ◽  
Pollen Dispersal ◽  
Pollen Grains ◽  
Physical Characteristics ◽  
Araucaria Angustifolia ◽  
Effective Population ◽  
Pollen Dispersion ◽  
Biological Studies ◽  
Seed Dispersion ◽  
Dispersion Patterns

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.

scholarly journals Floral biology of Senecio macrophyllus M. BIEB. (Asteraceae), a rare Central European steppe plant

2014 ◽  
Vol 83 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Bożenna Czarnecka ◽  
Bożena Denisow
Keyword(s):  
Rare Species ◽  
Pollen Viability ◽  
In Situ Conservation ◽  
Pollen Grains ◽  
Main Function ◽  
Long Distance ◽  
Early Afternoon ◽  
Pollen Presentation ◽  
Insect Visitors

Knowledge of the flowering phase and plant pollination ecology is very important for understanding the life history of long-lived perennials. In the case of rare species, the information may have implications for conservation practices. Our studies on flower morphology and blooming biology of the vulnerable plant <em>Senecio macrophyllus</em> M. BIEB. were conducted in situ (flowering, activity of insect visitors) in the largest population in SE Poland and in laboratory (light and scanning electron microscopy). The disc florets open diurnally with most intensive anthesis in the early afternoon and attract insect visitors with nectar and pollen. In highly protandrous disc florets, pollen viability decreases in time, whereas stigma receptivity increases. The upper part of the pistil forms a brush-like pollen presenter, covered with unicellular trichomes with chromoplasts. Pollen presentation lasts 4–11 hours per floret, and 8 days in a single head, the main function of which is to extend the availability of male gamets for reproduction. The number of florets per head, the head size, and the number of pollen grains produced per anther, and the pollen grain viability differed significantly between microsites. The finding indicates that, apart from the biotic factors, abiotic conditions may considerably influence generative reproduction of the species. In the study area, the principal visitors of <em>S. macrophyllus</em> flowers were Hymenoptera, with predominance of <em>Apis mellifera</em> (53.4% of visits). The remarkable share of butterflies (13.9%) recognized as the long-distance moving insects may improve the genetic variability of individuals within a fragmented population. A more detailed study is necessary to explain the role of insect visitors in effective pollination and in gene transfer between patches. The assessment of optimal conditions for the generative reproduction is fundamental for the in situ conservation of this rare species.

scholarly journals Elaborated pollen packaging and dispensing mechanism induced by petal architecture from a Papaveraceae species

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7066
Author(s):  
Shanlin Yang ◽  
Guangming Chu ◽  
Xiang Shi ◽  
Shaoming Wang
Keyword(s):  
Mating System ◽  
Pollen Grains ◽  
Middle Lobe ◽  
Mixed Mating ◽  
Pollination Efficiency ◽  
Pollen Transfer ◽  
Mixed Mating System ◽  
Secondary Pollen Presentation ◽  
Pollen Presentation ◽  
Total Pollen

Secondary pollen presentation (SPP) is a reproductive strategy that enhances the efficiency of pollen transfer, which has been explored for more than 200 years, resulting in 10 identified types of SPP. The ephemeral plant Hypecoum erectum L. (Papaveraceae) has an elaborate petal structure. The middle lobe is a key functional organ in SPP. To explore the importance of the middle lobe structure, we measured the flowering process, the curling movement and growth of the middle lobe, pollination characteristics, pollination efficiency, and the mating system in H. erectum in the field. The yellow middle lobe structure had an important role in attracting pollinators. The middle lobes on the inner petals function as a redundant cucullate structure and wrapped about 84% of the total pollen grains as soon as the anthers dehisced. These then grew upward and gradually presented pollen to pollinators via the roll out of the middle lobes. One bee species, Colletes vestitus from Colletidae, was the only effective pollinator of H. erectum. The SPP mechanism increased the efficiency of pollen transfer by C. vestitus. The middle lobes, which wrapped pollen and grew upward, contacted the stigma and provided an advantage for self-pollination and outcrossing by growing upward higher than the corolla. Hypecoum erectum L. has a mixed mating system with selfing and outcrossing. Thus, the SPP mechanism plays a key role during the pollination process and is necessary for improving pollination efficiency and promoting reproductive success.

scholarly journals MONOCOT POLLEN FLORA OF PASCHIM MEDINIPUR DISTRICT, WEST BENGAL WITH A NOTE ON POLLEN DISPERSAL MECHANISM

2017 ◽  
Vol 8 ◽  
Author(s):  
Arundhati Ghosh ◽  
Prakash Karmakar
Keyword(s):  
Light Microscopy ◽  
West Bengal ◽  
Pollen Dispersal ◽  
Pollen Grains ◽  
Surface Features ◽  
Dispersal Mechanism ◽  
Morphological Studies

<p>During the present investigation pollen morphological studies of 66 species belonging to 19 families of monocots in Paschim Medinipur district have been worked out by light microscopy. The studied families are Agavaceae, Amaryllidaceae, Arecaceae, Asphodelaceae, Cannaceae, Colchicaceae, Commelinaceae, Costaceae, Cyperaceae, Hemerocallidaceae, Hydrocharitaceae, Iridaceae, Liliaceae, Limnocharitaceae, Musaceae, Poaceae, Pontederiaceae, Typhaceae and Zingiberaceae. The apertural patterns are mostly belong to two different categories viz. monosulcate form (Agavaceae, Amaryllidaceae, Arecaceae, Asphodelaceae, Colchicaceae, Commelinaceae, Costaceae, Hemerocallidaceae, Hydrocharitaceae, Iridaceae, Liliaceae, Limnocharitaceae, Musaceae, Poaceae, Pontederiaceae) and anaporate type (Cyperaceae, Poaceae and Typhaceae). The shape of the pollen grains with monosulcate apertures are mostly oblate to peroblate type whereas taxa showing anaporate apertures are more or less spheroidal. Regarding the mode of pollen dispersal plant taxa with monosulcate apertures and apiculate surface ornamentations (e.g., reticulate, rugulate, spinulate, verrucate) are entomophilous (mainly melittophilous) whilest anaporate with smooth or minutely apiculate surface features are anemophilous. Here, entomophilous taxa provide rewards as pollen grains and nectar to the honeybee speecies, therefore, contribute as resource mobilizer for sustainance of honeybee colonies. </p>

scholarly journals Pollen Grains in Lake Sediments: Pollen Percentages in Surface Sediments from Southern Michigan

1971 ◽  
Vol 1 (4) ◽  
pp. 450-467 ◽  
Author(s):  
M. B. Davis ◽  
L. B. Brubaker ◽  
J. M. Beiswenger
Keyword(s):  
Deep Water ◽  
Surface Sediments ◽  
Pollen Dispersal ◽  
Pollen Grains ◽  
Deciduous Tree ◽  
Lake Basin ◽  
Tree Pollen ◽  
Chi Square ◽  
Early 19Th Century ◽  
Washtenaw County

Pollen in surface sediments from five lakes in southern Michigan shows evidence of differential deposition. In most lakes, pollen from ragweed occurs in a higher ratio to tree pollen in shallow-water sediment than in deep water. Pine and certain herbs with small pollen grains follow the same pattern. One very deep lake is an exception, with the ratio of ragweed to tree pollen highest in deep-water sediment. Pollen from local aquatics and from willow, which grows along the lake shore, is also unevenly distributed, occurring in highest frequencies near the parent plants. Pollen from deciduous trees, however, occurs in similar ratios at all sampling stations within each lake. Deciduous pollen occurs in uniform ratios, also in older sediment, deposited in the early 19th century, when the landscape was still forested.Percentages of deciduous tree pollen (as percent tree pollen) were compared among lakes. Single samples were taken for this purpose from the deepest part of each lake basin. Oak pollen percentages are higher in three lakes in western Washtenaw County than in three lakes in eastern Washtenaw County. This difference reflects a similar difference in present-day vegetation: second-growth oak forests grow near the lakes in the western half of the county, while all but 5% of the area in the eastern part of the county is farmland. (The difference in the ratio of farmland to forestland in the two parts of the county is not reflected clearly in the ratio of herb pollen to tree pollen, because there is so much variation within each lake.) In 140-year-old sediment, on the other hand, tree pollen percentages in the six samples are homogeneous as shown by a chi-square test. The homogeneity in sediment deposited before the forest was cleared is surprising, because witness-tree data from presettlement time show that the frequencies of tree species in the two areas were quite different. Pollen dispersal at that time must have been effective enough, to counteract differences over distances of a few tens of kilometers in the amounts and kinds of pollen produced by the vegetation.

Adaptation of male reproductive structures to wind pollination in gymnosperms: Cones and pollen grains

2011 ◽  
Vol 91 (5) ◽  
pp. 897-906 ◽  
Author(s):  
Y. Lu ◽  
B. Jin ◽  
L. Wang ◽  
Y. Wang ◽  
D. Wang ◽  
...  
Keyword(s):  
Pollen Dispersal ◽  
Digital Camera ◽  
Morphological Characteristics ◽  
Pollen Grains ◽  
Wind Pollination ◽  
Ancestral State ◽  
Physical Restraints ◽  
Pollination Success ◽  
Reproductive Structures ◽  
Evolutionary Response

Lu, Y., Jin, B., Wang, L., Wang, Y., Wang, D., Jiang, X.-X. and Chen, P. 2011. Adaptation of male reproductive structures to wind pollination in gymnosperms: Cones and pollen grains. Can. J. Plant Sci. 91: 897–906. Wind pollination (anemophily) in gymnosperms is thought to be an ancestral state. Previous studies considered wind pollination to be a largely random phenomenon, but recent evidence suggests that wind-pollinated species have evolved different complex reproductive adaptations for controlling and maximizing the success of wind pollination. However, compared with angiosperms, wind pollination in gymnosperms is poorly understood. We investigated the male reproductive structures of 13 representative gymnosperm species using a scanning electron microscope and digital camera, and analyzed how the morphological characteristics of male cones and pollen facilitate pollination. These characteristics showed a surprising variation between different gymnosperm species in improving pollination success. For example, the relationship between the position of the male cone and the surrounding vegetative structures is adjusted to optimize pollen release. The pollen grains have sacs and papilla and exhibit particular shapes after release from microsporangia, including boat-like, saccate, papilla-like and spheroid shapes, which facilitate pollen dispersal in the air. Taken together, our results suggest that the extensive diversity of male reproductive structures within gymnosperms represents an evolutionary response to long-term selection and results in solutions to the physical restraints of anemophily.

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