Secondary Pollen Research Articles

Atributos florais em um sistema de polinização especializado: Calathea cylindrica (Roscoe) K. Schum. (Marantaceae) e abelhas Euglossini

Sistemas de polinização especializados estão ligados a características que incentivam as visitas por polinizadores e desestimulam visitas por outros animais. O mecanismo de polinização de uma espécie de Marantaceae foi estudado com ênfase nessa questão. Calathea cylindrica é uma erva com flores disponíveis o ano todo. As flores são peculiares pela fusão e modificação dos elementos, assimetria, apresentação secundária de pólen, néctar pouco acessível e tubo longo, estreito e fechado até a visita do polinizador. A polinização consiste em um mecanismo explosivo, sendo que uma vez disparado, as estruturas florais não retornam à posição inicial. Assim, há uma única possibilidade para transferência de pólen. Os polinizadores são fêmeas de abelhas Euglossini (Apidae) e no meio da manhã todas as flores já haviam sido visitadas. O acesso ao néctar em flores intactas requer a realização de movimentos específicos e com força apropriada, o que exclui outros insetos. A quantidade de néctar produzido em flores ensacadas foi em torno de 13 µL com 32% de concentração de açúcares. O néctar continua sendo secretado em quantidades pequenas depois do disparo do mecanismo. A floração contínua, a quantidade alta de néctar produzido e a continuidade de secreção após a polinização parecem promover maior fidelidade dos polinizadores. A complexidade estrutural das flores, a secreção que banha externamente a câmara nectarífera e o tubo estreito com pelos internos dificultam o acesso ao néctar e parecem funcionar como barreiras para outros visitantes. Em conjunto, esses fatores parecem ser os determinantes do alto grau de especialização do sistema.

Pollen analysis of honeys from Mediterranean region of Anatolia

Twenty‐five samples of honey from different localities of the province, Anatolia, in the Mediterranean were examined for pollen content. Eleven samples were unifloral (>45% pollen of one taxon in sample) with three being unifloral for Apiaceae, two for Pimpinella anisum, two for Raphanus raphanistrum, one for Eucalyptus spp. one for Cirsium sp., one for Plantago sp. and one for Ulmus sp. Pollen analysis indicated 91 pollen forms of which 70 came from nectariferous and 21 from nectarless plants. The honeys had contained 14 to 36 different types of pollen. The average number of pollen types per honey was 22. Secondary pollen components were from 11 taxa: Anthemis sp., Astragalus sp., Citrus sp., Euphorbia sp., Ferula sp., Rosa sp., Rhamnus sp., Olea europaea, Salix sp., Pimpinella anisum and Trifolium sp. Fifty‐nine pollen types occurred as ‘important minor’ types. Apiaceae, Asteraceae, Fabaceae and Rosaceae were the most represented families. Although, the honeys of citrus were collected throughout southern Anatolia, Citrus sp. was not particularly attractive to foragers nor was it major pollen or nectar sources in this region.

Secondary pollen presentation in Cuban bat pollinated Lobelia: precise deposition of pollen and mechanical species isolation

Secondary pollen presentation in Cuban bat pollinated Lobelia: precise deposition of pollen and mechanical species isolation

Stamens and mimic stamens as components of floral colour patterns

Lunau, K.: Stamens and mimic stamens as components of floral colour patterns. — Bot. Jahrb. Syst. 127: 13–41. 2007. — ISSN 0006-8152. Dedicated to Professor Dr. Gunther Osche, Freiburg im Breisgau (Germany), on the occasion of his 80th birthday; he discovered the phenomenon of mimic stamens when re-assessing floral colour pattern with his eyes newly tuned by Wicklerian thoughts about automimicry. Stamens of zoophilous plants are multifunctional floral organs which protect pollen against environmental stress, attract potential pollinators, attach pollen to the sites of secondary pollen presentation, or to the pollinator’s body surface, and provide pollen as a reward for flower-visitors. Pollen-eating flower-visitors such as syrphid flies and pollencollecting flower-visitors such as bees innately respond to visual and chemical cues of stamens and pollen prior to individual experience. Flowering plants presenting conspicuous stamens and pollen to attract pollinators incur numerous costs associated with visual exposure of pollen including investments for protection against solar radiation, pollen losses caused by wind, rain, and illegitimate flower-visitation, and pollen losses due to consumption of pollen by flower-visitors or pollinators. Many flowers use mimic stamens (e.g. staminodes, false stamens, yellow floral guides in the size and shape of anthers) and thus overcome these disadvantages. Several study cases focus on the benefits of signaling with mimic stamens in flowering plants having polymorphic flowers, distinct flowering phases, and hidden real pollen. The aim of this review is to illustrate the various cases in which flowering plants may benefit from attracting flower-visitors by means of mimic stamens.

Remobilization of initially deposited pollen grains has negligible impact on gene dispersal in bumble bee‐pollinated Brassica napus

1 The transfer of pollen among flowers is an important determinant of mating patterns in plants, and considerable attention has been devoted to understanding animal-mediated pollen transfer and its causal mechanisms. Conventionally, pollen carryover has been envisioned as a one-step process, but a pollen grain's journey may not be so simple. Potentially, pollen deposited on a flower's stigma could be remobilized and transferred to the stigma of a second flower. Alternatively, pollen may be deposited on unreceptive floral surfaces, such as petals, by either a pollinator or the wind and then remobilized and transferred to the stigma during a pollinator visit. 2 We quantified the potential for secondary dispersal of pollen by bumble bees (Bombus terrestris L.) visiting flowers of Brassica napus L., chosen because it typifies a generalized animal-pollinated flower and because of concern about pollen escaping from genetically modified varieties in agriculture. 3 We tested whether genetically marked pollen that was initially deposited by a bumble bee on a flower's stigma could later be transferred by another bee and thereby fertilize ovules on a different flower. In a second experiment, we tested whether marked pollen deposited on a flower's petals (as if by a pollinator or the wind) could later be transferred to the stigma by a bee and thereby fertilize the flower's ovules. In both experiments, the numbers of genetically marked progeny were recorded and a model was developed to quantify the relative effectiveness of direct vs secondary pollen dispersal. 4 Our analysis revealed that only small numbers of pollen grains achieved secondary dispersal by a pollinator, and that the probability of fertilization being achieved through secondary dispersal was minute.

Estrutura sexual e ecologia reprodutiva de Amaioua guianensis Aubl. (Rubiaceae), uma espécie dióica de formações florestais de cerrado

The breeding biology of Amaioua guianensis was studied in a forest area at Parque do Sabia in Uberlândia, MG, Brazil, between September 2003 and April 2005. Phenology, breeding system, flower morphology, pollinator and disperser's assemblages, and sexual structure of the reproductive individuals were investigated. Amaioua guianensis is a woody dioecious species common in Brazilian forest areas. Flowers are hexamerous, tubular, whitish and odoriferous, pollinated by relatively specialized vectors as large bees and hawkmoths. Pistilate flowers produced nectar earlier and in larger amounts than the staminate ones. Staminate flowers were produced in larger numbers per inflorescence and were significantly larger than the pistilate ones. Flowers were presented in terminal inflorescences, composite umbels in the staminate and simple ones in pistilate individuals. Both male and female flowers produced non-functional sexual structures of the opposite morph, but the style of male flowers act as a pseudo-stamen, a secondary pollen presentation mechanism which is common in the tribe Gardenieae but had not been described previously to the species. Sexual ratio was significantly male biased and gender was distributed contagiously in the area, probably due in both cases to vegetative multiplication and disturbance. Natural pollination was as high as 98.6% and fruit set was 75.7%. Apomictic fruit production was very low (3.4%). Fruits were dispersed by birds. Floral morphology and relatively specialized pollinator's fauna rendered efficient pollination service and fruit production in the species even in the relatively disturbed study area.

Regional Differentiation in the Dynamics of the Pollen Seasons of Alnus, Corylus and Fraxinus in Poland (Preliminary Results)

In 1995–1996 a study of pollen concentrations of Corylus, Alnus and Fraxinus was performed at seven sites in regions of different climatic and natural conditions. The aim of the study was to determine whether regional differences in the course and duration of pollen seasons occur in Poland. The study was performed using a volumetric method. Several phases during the pollen season were defined for each taxon (1, 2.5, 5, 25, 50, 75, 95, 97.5, 99% of annual total) and duration of the pollen seasons was calculated using 98 and 90% methods. Dynamics and duration of the pollen seasons and a start of particular phases of the season were compared among sites. On the basis of the preliminary analysis it could be supposed that regional differences were most evident in the case of Corylus. The pollen season of this taxon started the earliest in Poznan where thermal conditions were most favourable and the latest in Gdansk, a place at the furthest to the north (χ 2, α≤0.05). In montane regions (Zakopane, Rabka) last phases of the season were significant extended (χ 2, α≤0.05). Probably it results from secondary pollen deposition and a long-distance transport by montane wind. In case of Fraxinus the significant regional differences in the start of the pollen season were not found. The study supported that weather conditions have the substantial influence on the start of consecutive phases of the pollen season.

Flower morphology and pollination in Mikania (Asteraceae)

Summary Morphological and functional changes of the floret whorls of Mikania urticifolia Hook. et Arn. (Asteraceae, Eupatorieae) in relation to pollination and the role of floral visitors have been observed in two Argentine localities. Flowers are dichogamous protandrous with secondary pollen presentation (“brushing” type). This feature favours cross-pollination over autogamy, but both reproductive systems coexist and they complement each other. The heads were visited by insects from different orders such as Hemiptera, Coleoptera, Lepidoptera, Hymenoptera and Diptera during the third floral phase (middle anthesis) and the beginning of the fourth phase (late anthesis). Hymenoptera, particularly bees are the most important pollinators because of their number and their diversity.

Palynological differences in the pollen content of Eucalyptus honey from Australia, Portugal and Spain

A melissopalynological study was carried out on 75 samples of Eucalyptus honey from different countries (22 from Australia, 13 from Portugal and 40 from Northwest Spain), in which a total of 145 different pollen types were identified. Of such, only Eucalyptus, Acacia, Brassica, Echium, Ligustrum, Plantago, Rumex, Taraxacum, Trifolium and Vicia pollen are present in the honeys from all three countries. Among the most abundant pollen types in Australian honeys, those belonging to the following families stand out: Myrtaceae (Angophora and Melaleuca), Fabaceae, Asteraceae, Proteaceae and Euphorbiaceae, along with Raphanus, Echium and Citrus. In the Portuguese honeys, the presence of Fabaceae, Rosaceae and Cistaceae stands out, with Castanea and Erica as secondary pollen types, while Fabaceae, Asteraceae, Boraginaceae, Cistaceae and Scrophulariaceae are the families with the highest quantity of pollen types in the samples from Spain. In the latter, the most important secondary pollen types are: Castanea, Cytisus, Erica, Lotus, Salix and Rubus.

Intraannual variations in the pollinic spectrum of honey from the lower valley of the River Chubut (Patagonia, Argentina)

Thirty honey samples from the lower valley of the River Chubut, obtained by successive harvests in five apiaries overtwo consecutive apicultural periods (between 1997 and 2000) were analysed. Three hives per apiary were selected, fromwhich three successive harvests were obtained at the end of the following periods: initial (September 1st-December 20th),middle (December 20th-January 30th) and final (January 30th-March 15th). Pollen types were identified by comparisonwith a reference collection. Both reference pollen and sample pollen were subjected to acetolysis. A total of fifty entomophilouspollen types were identified: thirty-six, thirty-five and thirty-seven in initial, middle and final periods,respectively. The most abundant pollen was similar over the whole season, due to the long flowering periods of the taxaproducing dominant and secondary pollen. Tamarix gallica and Medicago sativa were main sources of nectar duringthe entire production period. Significant differences (P

Rubiacearum Americanarum Magna Hama Pars XII. A New Species of Ixora (Ixoreae) from Panama

terminal, cauliflorous, or ramiflorous. The fragrant flowers are homostylous and generally white, yellow, or red. In her excellent revision of Ixora in Africa, De Block (1998) also highlighted the petiole bases, which are articulated from the stems (at least in dried specimens) in Ixora, as a good character for recognition of this genus. This character is found in Neotropical Ixora species as well. Other Neotropical Rubiaceae genera have not yet been widely surveyed for this feature; articulated petiole bases are known in a few other paleotropical genera, of several different tribes. The inflorescence axes of Ixora are also usually articulated, often giving them a distinctive appearance when dry. The flowers of Ixora exhibit an adaptation for pollination that is more common in Rubiaceae of the Paleotropics than the Neotropics, called secondary pollen presentation. The flowers of Ixora species are protandrous, and the anthers in bud are held closely around the style and stigmatic arms. Rather than presenting their pollen directly to pollinators, the anthers release and transfer some or all of their pollen onto the upper part of the style and the non-receptive abaxial surfaces of the stigmatic arms. Then this transferred pollen is exposed to pollinators for some period of time on these structures; after this the stigmatic arms separate and the stigmatic surfaces become receptive. The inflorescences of Ixora are considered terminal, most often arising directly from the apices of the main stems but sometimes borne on short lateral stems produced in the leaf axils. These lateral stems are called short shoots bearing terminal inflorescences by De Block (1998). In some Neotropical species the stem portion of these short shoots may be reduced so that the inflorescences appear to be axillary (e.g., I. yavitensis Steyermark). The inflorescences of Ixora are usually regularly branched with the higher order axes as well developed as the axis from which they branch; this condition was called trichotomous by De Block (1998). The inflorescences may vary markedly among species of Ixora in their degree of expansion, from strongly congested, with the axes only ABSTRACT. The new species Ixora knappiae C. M. Taylor (Rubiaceae) from the San Blas region of Panama, described and illustrated here, is notable for its opposite, subsessile, basally rounded to cordate leaves.

Pollination Biology and Flower Visitors of the Gynodioecious Species Lobelia spicata Lam. (Campanulaceae)

Molano-Flores, B. (Illinois Natural History Survey-Center for Biodiversity, 607 E. Peabody Drive, Champaign, Illinois 61820). Pollination biology and flower visitors of the gynodioecious species Lobelia spicata Lam. (Campanulaceae). J. Torrey Bot. Soc. 129: 187-193. 2002.-The pollination biology and flower visitors of Lobelia spicata, an herbaceous prairie perennial, were examined, and this species was found to be xenogamous, self-compatible, and gynodioecious. Hermaphroditic individuals are protandrous, produce nectar, and have secondary pollen presentation (i.e., pump mechanism). Female individuals do not produce nectar. No significant differences were found between the fruit set of open-pollinated hermaphroditic and female flowers. In hermaphroditic bagged flowers seeds were produced (i.e., undeveloped fruits) suggesting self-pollination; however, this was determined to be the result of geitonogamous pollination by thrips. Autogamy is not likely in this species because there is no overlap between the staminate and pistillate phases. This species is pollinated mainly by bees from the genus Augochlorella. Overall, this study shows that L. spicata shares many common characteristics with other species of Lobelia (i.e., L. cardinalis and L. siphilitica) such as protandry, self-compatibility, no autonomous self-pollination, similar flower phenology (i.e., pistillate and staminate phases), and secondary pollen presentation (i.e., pump mechanism). In contrast to these other species, L. spicata blooms early, has smaller flowers, and attracts smaller pollinators.

Stigma of the African Genera Rutidea and Nichallea (Rubiaceae‐Ixoroideae‐Pavetteae): Highly Modified Receptive Surfaces

The tropical African genera Rutidea and Nichallea possess secondary pollen presentation, as do many other Rubiaceae, but the style‐stigma complex shows some special features. Style and stigma form one slender structure that terminates in a fusiform to clavate or broadly elliptic to globose head. The stigma consists of two permanently fused stigmatic lobes, a common enough situation within the Rubiaceae, but it is further differentiated into three zones: a narrow stigmatic base, a stigmatic head, and the free tips of the stigmatic lobes. The pollen‐receptive surfaces are highly modified. They are restricted to the adaxial sides of the free stigmatic tips and to the lines of fusion between the stigmatic lobes, visible as two longitudinal furrows on the style‐stigma complex. Compared to the structure of the style‐stigma complex in other genera of the Rubiaceae with permanently fused stigmatic lobes, a major morphological trend can be observed in Rutidea and Nichallea, notably the displacement of the pollen‐r...

Pollen spectrum of honey of "uruçu" bee (Melipona scutellaris Latreille, 1811).

In spite of the importance of the "uruçu" bee as honey producer of excellent quality, as well, potential pollinator both in agricultural and natural ecosystems, mainly in North-eastern Brazil, just some information is found in literature about sources that such bees utilize to collect nectar and pollen. The identification of the plants visited by Melipona scutellaris was accomplished with base on the analysis of pollen types found in the honey samples collected every two months, from March 1997 to February 1998, in 15 colonies located in Catu, State of Bahia, Brazil (12 degrees 21'00"S, 38 degrees 22'40"W, 76 m of altitude). Qualitative and quantitative analysis of the pollen types were carried out determining the percentage and occurrence classes. Twenty-eight pollen types were found, being considered dominant pollen, the Eucalyptus spp. and Psidium sp. types and secondary pollen, Bauhinia sp., Caesalpinia sp. and Mimosa verrucata types. It was verified dominant pollen of Eucalyptus spp. in honeys produced in November/December 1997 and January/February 1998. The families Caesalpiniaceae (14%), Mimosaceae (25%) and Myrtaceae (56%) were the most represented in the pollen spectrum.

Observations of airborne Cryptomeria japonica pollen in the summer

ABSTRACT Background : Airborne Cryptomeria japonica pollen has been detected from July to September, after the main pollen dispersal season (during florescence), in Toyama and Niigata prefectures, Japan. Methods : To identify the source of the pollen, two possible pathways were investigated: (i) secondary pollen dispersal from the ground; and (ii) release from male flowers remaining on the tree crown in C. japonica forests. Results : Secondary pollen dispersal from the ground ceased just after the main pollen dispersal season ended. However, male flowers remained on the crown until the end of September and released significant amounts of pollen, which contained as much allergenic Cry j 1 as normal pollen dispersed during the spring. There is a significant positive correlation between airborne pollen counts in the spring (February-May) and summer (June-September). Conclusions : These results indicate that the main sources of airborne pollen grains during the summer are male flowers remaining on the tree crown after their florescence.

Recent land-use and soil-erosion history within a small catchment in Connemara, western Ireland: evidence from lake sediments and documentary sources

Environmental magnetism, elemental chemistry, pollen, macrofossil, and radioisotopes were studied on top-metre cores from Ballydoo Lough, Connemara, western Ireland, to reconstruct the impact of changing farming practices on soil erosion in a lake catchment. Documentary evidence, including detailed agricultural statistics, gave an independent land-use history over the period represented in the sediment record, i.e. most of the last two centuries. Maximum soil erosion, which involved unweathered coarse material as well as topsoil, was associated with a rapidly rising rural population and increased arable activity during the early 19th century. The Great Famine (1845–1847) halved the population, but arable and especially pastoral farming quickly recovered and were maintained at a high level from the late 1850s until the late 1890s. During this time, the rate of soil erosion slowed down considerably and the contribution of coarse mineral material relative to topsoil declined. Erosion of peaty soils was less important as potato cultivation declined and the middle slopes of the catchment were no longer cultivated. From the end of the 18th century to the 1970s, sediment accumulation and erosion rates were less and progressive podzolisation occurred as pastoral and particularly arable farming declined. The uppermost sediments record a sharp increase in soil erosion, involving mainly organic-rich soils from the upper slopes. This increase is attributed to a sharp rise in livestock numbers, especially sheep. A feature of the pollen record is the high arboreal pollen representation (43%–66% of total terrestrial pollen), which consists mainly of secondary pollen. It indicates a substantial input of pollen-bearing organic detritus derived from peaty soils and peat cuttings in the catchment.

Reproductive biology ofWahlenbergia (Campanulaceae) endemic to Robinson Crusoe Island (Chile)

The reproductive biology ofW. berteroi, W. fernandeziana, and a putative hybrid betweenW. fernandeziana andW. grahamiae, endemic to Robinson Crusoe Island (Juan Fernandez archipelago, Chile) was studied. Flowers are hermaphroditic, protandrous, offer nectar, and exhibit secondary pollen presentation involving pollen collecting hairs on the style. These features imply allogamy and biotic pollination. However, male and female phases overlap and no effective pollinators were observed. Experimental data indicate these taxa are self-compatible and facultatively autogamous, a conclusion also suggested by the pollen/ovule ratios. Selfing is accomplished when the stigmatic lobes reflex and touch the style, except forW. berteroi where they do not reflex completely. Autogamy is accomplished in the latter when pollen grains deposited on the inner surface of the corolla throat by the “pollen brush” are gathered by stigmatic lobes when shaken by wind. The degree of autogamy, and perhaps self-compatibility, seems to be inconstant, as implied by the variable natural seed set (overall range 21–188 seeds per fruit). A mixed mating system — primarily outcrossing/entomophilous, but also autogamous — must have been present in the continental ancestors of these taxa. Autogamy promoting self-fertilization is important now — on an island with scarce pollinators — and in the past — when the first founders arrived.

Pollen grains: Why so many?

My objective is the examination of selective forces that affect pollen number. Relationships among other floral traits of animalpollinated plants, including pollen size, stigma area and depth, and the pollen-bearing area of the pollinator may affect pollen number and also provide a model to examine how change in one trait may elicit change in other traits. The model provides a conceptual framework for appreciating intra- and inter-specific differences in these traits. An equivalent model is presented for wind-pollinated plants. For these plants the distance between putative mates may be the most important factor affecting pollen number. I briefly consider how many pollen grains must reach a stigma to assure fruit set. I use pollen-ovule ratios (P/Os) to examine how breeding system, sexual system, pollen vector, and dispersal unit influence pollen grain number. I also compare the P/Os of plants with primary and secondary pollen presentation and those that provide only pollen as a reward with those that provide nectar as part or all of the reward. There is a substantial decrease in P/O from xenogamy to facultative xenogamy to autogamy. Relative to homoecious species the P/Os of species with most other sexual systems are higher. This suggests that there is a cost associated with changes in sexual system. The P/Os of wind-pollinated plants are substantially higher than those of animal-pollinated plants, and the available data suggest there is little difference in the pollination efficiency of the various animal vectors. The P/Os of plants whose pollen is dispersed in tetrads, polyads, or pollinia are substantially lower than those of species whose pollen is dispersed as monads. There was no difference in the P/Os of plants with primary and secondary pollen presentation. The P/Os of plants that provide only pollen as a reward were higher than those that provide nectar as a reward. All of these conclusions merit additional testing as they are based on samples that are relatively small and/or systematically biased.

Pollination and Reproductive Biology ofRauvolfia grandiflora(Apocynaceae): Secondary Pollen Presentation, Herkogamy and Self-Incompatibility

Pollination and Reproductive Biology of<i>Rauvolfia grandiflora</i>(Apocynaceae): Secondary Pollen Presentation, Herkogamy and Self-Incompatibility

Pollination and Reproductive Biology of Rauvolfia grandiflora (Apocynaceae): Secondary Pollen Presentation, Herkogamy and Self‐Incompatibility

Abstract: The pollination and reproductive biology of Rauvolfia grandiflora were studied in natural populations in the forest of the Recife Botanical Garden. R. grandiflora is a shrubby species (2 to 5 m), the flowers are hermaphrodite and salverform. The corolla tube is white and the five free lobes of the corolla are flushed with violet. The five stamens are attached to the corolla tube; the anthers are introrse and form a cone situated immediately above the stigmatic head. There is a space between the anthers and the stigmatic head, where the pollen is deposited. The stigmatic head has three functional regions: a) an upper sterile region; b) a median region that produces a sticky substance and c) a lower receptive region, which is located beneath a basal collar. The secondary pollen presentation and the herkogamy mechanisms are discussed. Sugar concentration in nectar was, on average, 31.7%. The pollen viability was 97.4%. R. grandiflora is melittophilous and in the study area was found to be pollinated by only one species of long‐tongued bee, Exaerete smaragdina. R. grandiflora was found to be self‐incompatible, and the percentage of fruit set under natural conditions was low.