Arecaceae potential for production of monofloral bee pollen

Bees often collect pollen from plants that are near their colonies or apiaries. Arecaceae are characterised by having species that flower throughout the year and produce large quantities of pollen. Pollen grains of Arecaceae have two main forms, namely monosulcate and trichotomosulcate. The study area is located in the coastal region of the state of Sergipe, Brazil, where large amounts of bee pollen are produced by Apis mellifera. This study aims to evaluate how Arecaceae contribute to the production of monofloral bee pollen. Samples of bee pollen loads were collected each month for two years (totalling 24 samples), acetolysed, and mounted on permanent slides. At least 500 grains of pollen were counted for each sample, the data was analysed, and figures were made using the Tilia software. The pollen grains of Cocos nucifera were present in 23 samples (96%), and concentrations of this pollen type varied between 1.1 and 46.8% (but were commonly above 20%). The concentration of Arecaceae pollen grains is the result of the large-scale production of coconuts along the coastline. However, the presence of other pollen types, such as Mimosa arenosa, Mimosa pudica, Mikania and Myrcia, compliments the diets of bees in the region. The results show that even when in low frequency, Cocos nucifera pollen grains represent a large proportion of pollen content compared with other pollen types, because of the large size of Arecaceae pollen grains.     

High-throughput procedure for single pollen grain collection and polymerase chain reaction in plants

Single pollen grain polymerase chain reaction （PCR） has succeeded in several species, however only limited numbers of pollen grains were involved due to difficulties in pollen isolation and lysis. This has limited its application in genetic analysis and mapping studies in plants. A high-throughput （HT） procedure for collecting and detecting genetic variation in a large number of individual pollen grains by PCR is reported. The HT procedure involved the collection of individual pollen grains by a pair of special forceps and the lysis of pollen grains in a heated alkali/detergent solution followed by neutralization with a tris-ethylenediamine tetraacetic acid （TE） buffer. These resulting template solutions yielded PCR reactions involving the 5S ribosomal RNA intergenic spacers, randomly amplified polymorphic DNA, and simple sequence repeats markers. Using this procedure, one person with experience could collect and process up to 288 single pollen grain PCR reactions per day. The method worked well on sugarcane, corn, Miscanthus spp., snap bean, sorghum, and tomato. The ability to collect and conduct PCR on individual pollen grains on a large scale offers a new approach to genetic analyses and mapping studies in an easily controllable environment with a considerable cost reduction. The method will also significantly benefit studies in species that are difficult subjects for classical genetic research.     

Seed hairs of poplar trees as natural airborne pollen trap for allergenic pollen grains

The present article deals with the efficacy of seed hairs of poplar trees (Populus spp.) as a potent natural airborne pollen trap. Different species of Populus are commonly found planted along the streets in the cities of North China. The seed hairs and pericarp of poplar trees were collected from the trees and on the ground in Beijing Botanical Garden of Chinese Academy of Sciences and around Miyun Reservoir during May 2005 for pollen analysis. Different pollen spectra are recorded from different samples and are characterised by dominant occurrence of pollen grains of arboreal and anemophilous plants. In addition, pollen grains of non‐arboreal plants including grasses are also found trapped. Among the 46 trapped pollen grains, 26 are known to be allergenic. This study suggests that poplar seed hairs possibly make people feel uncomfortable due to the presence of allergenic pollen trapped in the hairs.     

A photographic account of pollen digestion by adult hoverflies

ABSTRACT. The method of pollen digestion by adults of the hoverfly Cheilosia albitarsis Mg. (Diptera: Syrphidae) was investigated by observing pollen grains at different stages in their progression along the gut. No form of mechanical 'grinding' to break up the grains was observed, as suggested by some previous authors. Instead, there was an exudation of the pollen grain contents through one of the pores in the pollen exine. This exudation may start as a growing pollen tube. The exact conditions which cause the pollen grains to give up their contents in this way are unknown, but it is suggested that nectar sugar within the gut may provide the necessary stimulus.     

樱属花粉形态研究

本文对樱属(Cerasus)9个种和变种的花粉形态进行光学显微镜观察,并结合电镜观察结果进行初步比较。结果表明,樱属花粉的极面观为圆形或近三裂圆形,赤道面观为椭圆形,三孔沟,外壁纹饰多为条纹状。属内特征基本一致,但种间存在着花粉大小、外壁纹饰的细微差别。     

Pollen gene expression analysed by micro-isoelectric focusing of proteins from isolated pollen grains in Cucurbita pepo L.

Summary Isoelectric focusing of proteins from single pollen grains of Cucurbita pepo L. has been developed for large scale study of pollen grain populations' heterogeneity. Forty to forty-five protein bands from one pollen grain are revealed after silver staining. Applications of this technique to pollen grain populations from different genotypes are described in this paper. Possible applications and limits of this technique are discussed with respect to plant breeding especially for the measure of gene frequencies in pollen grain populations.The work was partly supported by a grant from LIMAGRAIN and AGPM     

Isolation of Allium pollen protoplasts

Studies on protoplasts isolation were carried out with mature pollen grains of 29 samples of species of Allium aflatunense, A. cepa, A. fistulosum, A. karataviense, A. longicuspis, A. nutans, A. odorum, A. sativum and A. schoenoprasum. Surface sterilized pollen grains drifted from crushed anthers were incubated in an enzyme solution containing 1% (w/v) cellulase Onozuka R-10, 1% (w/v) Macerozyme R-10, 0,5 mol l^-1 sucrose and the basal salts of Nitsch medium. Protoplasts were released within 3 to 120 min, either from the pollen grain, through a slightly disturbed germination pore (narrow aperture), or through a wider aperture, when the exine surrounding the germination pore was disturbed. For the first time, protoplasts were obtained from 13 genotypes of 6 Allium species, at a rate of 1 to 30% of the digested intact pollen grains, depending on the genotype.     

Numerical modelling of pollen dispersion on the regional scale

New parameterisations were developed to calculate the emission and resuspension flux of pollen grains. These new parameterisations were included in the comprehensive mesoscale model system KAMM/DRAIS. Two types of simulations were performed. In the first case, horizontally homogeneous meteorology was assumed. In this case, pollen concentration rapidly decreased with the distance from the source. In the second case, where the fully three-dimensional model was applied, atmospheric lifetime of the pollen grains increased remarkably. This was mainly caused by the vertical wind speeds induced by topographic effects. Consequently, the pollen grains could travel much larger distances until they were deposited and finally removed from the atmosphere. This is an important finding with respect to the problem of cross pollination. Due to the lack of measurements, a number of parameters had to be assumed. However, the parameterisation proposed may well serve as a starting point of a daily pollen forecast with numerical models.     

Pollen histochemistry and pollen : ovule ratios in Zingiberaceae

BACKGROUND AND AIMS: Pollen grains of 37 species from 11 genera in the family Zingiberaceae were examined to assess qualitatively starch or lipid contents; the pollen grain and ovule numbers per flower and pollen : ovule ratios were also counted and calculated. Pollen : ovule ratios were studied to reveal patterns of variation in the Zingiberaceae. METHODS: Freshly open flowers with dehiscing anthers were collected at random from plants growing in natural habitats or in botanical gardens. Presence of lipids or starch in pollen grains was tested by Sudan solution and IKI solution, respectively, and examined under a microscope. To estimate the pollen and ovule numbers per flower, one anther from each bud was carefully dissected and all pollen grains were counted; ovaries were carefully dissected out of each flower and counted. Whenever possible, at least 10-15 buds were used in the determination. KEY RESULTS: Thirty-three of all the 37 species examined had starchy pollen. Starch was not found in only four species and lipid was not found in only one species; among the four tribes in subfamily Zingiberoideae, all species of Zingibereae and Globbeae had pollen with no starch, Alpineae and Hedychieae had pollen with and without starch, whereas, all species of subfamily Costoideae had starchy pollen with abundant lipids. The mean pollen : ovule ratios in the members of the Zingiberaceae investigated range from 3.25 +/- 1.56 to 616.52 +/- 117.83. CONCLUSIONS: The pollen nutrition types seemed not related to mating systems. The pollen : ovule ratios in members of the Zingiberaceae with the same breeding system are noticeably lower than those recorded by previous authors. The lower pollen : ovule ratios in this family are presumed to be related to the highly efficient pollination systems, mediated by pollen which can be quite glutinous and the relatively large stigma area. In most of the Alpinia species the anaflexistylous flowers have much larger numbers of pollen grains and higher pollen : ovule ratios than the cataflexistylous flowers. There are significant differences in mean pollen grain numbers and pollen : ovule ratios between different life forms but ovule numbers are approximately the same.     

Development of a semi-automatic system for pollen recognition

A semi-automatic system for pollen recognitionis studied for the european project ASTHMA. The goal of such a system is to provideaccurate pollen concentration measurements. This information can be used as well by thepalynologists, the clinicians or a forecastsystem to predict pollen dispersion. At first,our emphasis has been put on Cupressaceae, Olea, Poaceae and Urticaceae pollen types. The system is composed of two modules: pollengrain extraction and pollen grain recognition. In the first module, the pollen grains areobserved in light microscopy and are extractedautomatically from a pollen slide coloured withfuchsin and digitized in 3D. In the secondmodule, the pollen grain is analyzed forrecognition. To accomplish the recognition, itis necessary to work on 3D images and to usedetailed palynological knowledge. Thisknowledge describes the pollen types accordingto their main visible characteristerics and tothose which are important for recognition. Somepollen structures are identified like the porewith annulus in Poaceae, the reticulum in Oleaand similar pollen types or the cytoplasm inCupressaceae. The preliminary results show therecognition of some pollen types, likeUrticaceae or Poaceae or some groups of pollentypes, like reticulate group.     

Heterospecific pollen transfer between sympatric species in a midsuccessional old-field community

The cumulative (season-long) incidence of heterospecific pollen transfer (HPT) was examined using nine sympatric species in a midsuccessional old field. Inflorescences were collected weekly during the flowering season, and the proportion of foreign pollen/stigma was recorded. Flowering phenologies of sympatric species and ovule and seed counts of study species were also recorded. Heterospecific pollen was detected on some stigmas of each species. Medicago sativa (Fabaceae) received the most foreign pollen; in some cases, all of the grains on a stigma were heterospecific. Lotus corniculatus (Fabaceae) received the least amount of foreign pollen; the incidence of heterospecific pollen was near zero in most cases. The mean and range of foreign pollen received varied by as much as an order of magnitude between species. The six species with zygomorphic flowers, all Fabaceae, received more heterospecific pollen than the three species with actinomorphic flowers, Potentilla recta and P. simplex (Rosaceae) and Ranunculus acris (Ranunculaceae). This probably reflects a bias because our data were analyzed on a cumulative basis and the Fabaceae had longer flowering phenologies. HPT was not correlated with the species' relative abundance within the community. Proportion of foreign pollen received varied temporally within species, and this variation generally was not related to phenology of any sympatric taxa or the species' own phenology. Pollen grain diameter was positively related to levels of foreign pollen received by species. This might be caused by poor adhesion of large pollen grains to small stigmatic papillae or if generalist pollinators carrying large amounts of heterospecific pollen visit the large-grained species and specialists with little foreign pollen visit the small-grained species. The large proportions of heterospecific pollen on stigmas of many species indicate that HPT occurs frequently in the community we studied and the implications may include reduced seed set because of occlusion by foreign grains. As yet, however, it is unclear how important a factor HPT is in mediating pollen limitation of reproductive success.     

The pollinium ofLoroglossum hircinum (Orchidaceae) between pollination and pollen tube emission

The structure of the massulae composing the pollinium ofLoroglossum hircinum was studied before pollination and 12 and 24 hours afterwards. The grains are grouped in tetrads closely packed in massulae. The exine is only present on the outside of the massulae. The intine consists of two layers: a compact layer surrounding the pollen grain and a looser layer surrounding the pollen grain and a looser layer surrounding the tetrad. Twelve hours after pollination, pollen volume and the space between the tetrads increase due to vacuolization. Twenty-four hours after pollination, pollen volume and tetrad spacing are higher due to vacuolization and some grains have emitted pollen tubes. Pollen growth due to vacuole formation, and the absence of common walls between adjacent tetrads lead to crumbling of the massulae. The mature pollen grain does not have apertures: the site of pollen tube emission is determined after pollination. The first grains to germinate are those in the centre of the massula. The vegetative cell nucleus is the first to enter the pollen tube; the generative cell elongates and undergoes the second haploid mitosis shortly after entering the pollen tube.     

The influence of relative humidity on the swelling of pollen grains in vitro

The volume of hydrated pollen grains of Petunia hybrida L. during swelling in germination medium increased three times. The volume of desiccated pollen grains increased only two times after transfer to the same medium. This difference in swelling ability is attributed to different rigidities of the pollen grain wall,ccaused by the different hydration states. The relationship between pollen grain swelling and germination metabolism with regard to relative humidity is discussed.Abbreviation RH relative humidity     

Analysis of airborne pollen fall in Sakarya, Turkey

In this study, pollen grains were identified using Durham sampler in the atmosphere of Sakarya in 2000 and 2001. During these two years, a total of 10 805 pollen grains were recorded. A total of 5 386 pollen grains per cm² were recorded in 2000 and a total of 5 419 pollen grains per cm² in 2001. Pollen fall in the years 2000–2001 comprised grains belonging to 40 taxa and some unidentified pollen grains. Of these taxa, 22 belonged to arboreal and 18 taxa to non arboreal plants. Total pollen grains consisted of 69.45% grains from arboreal plants, 28.11% grains from non-arboreal plants and 2.44% unidentified pollen grains. In the region investigated, Gramineae, Pinus sp., Quercus sp., Cupressaceae/Taxaceae, Salix sp., Platanus sp., Populus sp., Carpinus sp., Fagus sp., Chenopodiaceae/Amaranthaceae, Xanthium sp., Moraceae, Corylus sp., Fraxinus sp., and Urticaceae released the greatest amount of pollen. The season of maximum pollen fall was from March to May, with a prevalence of arboreal pollen in the first months, and of pollen from non-arboreal plants in the last months of the year.     

Systematic significance of pollen arrangement in MICROSPORANGIA OF POACEAE AND Cyperaceaei REVIEW AND OBSERVATIONS ON REPRESENTATIVE TAX A

An anatomical survey of anthers of the Poaceae and Cyperaceae and two related families, the Restionaceae and Flagellariaceae, was conducted to determine the taxonomic distribution and possible phylogenetic significance of pollen arrangement. An unusual pollen arrangement was known from a small number of taxa in the Poaceae and Cyperaceae, in which a single, uniseriate cylinder of pollen grains is arranged in the anther locule such that each grain is in contact with the tapetum (termed here “peripheral” pollen). This contrasts with the prevailing arrangement in other angiosperms in which the locule contains a relatively large number of pollen grains in no special configuration, with many interior grains that never touch the tapetum (termed here “central” pollen). A total of 48 species in these four families was examined in this study, and observations on pollen arrangement for numerous additional species in these families were gleaned from the literature. We confirm that the peripheral arrangement is predominant in Poaceae and Cyperaceae, although both families also include species with central pollen, whereas only central pollen is found in Restionaceae and Flagellariaceae. In the peripheral arrangement, the pore of the pollen grain or pseudomonad, when observed, is in contact with the tapetum, but it has not been definitively demonstrated that this is always the case. Peripheral pollen in the Poaceae and Cyperaceae is nonhomologous because of the presence of pseudomonads in the latter family. It remains unexplained why peripherally arranged pollen or pseudomonads, with the attendant reduction in the number of pollen grains, should be associated with anemophily in these two families.     

Lectins of the <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> pollen grain walls stimulating in vitro pollen germination

Proteins diffusing from tobacco pollen grains into external medium, being inactivated by low temperature (0°C), were shown to stimulate pollen germination in vitro. Fractionation of these proteins by affinity chromatography using α-D-methylmannopyranoside (MMP) immobilized on agarose resulted in the isolation of lectins stimulating germination. The mol wts of these lectins were estimated by SDS-PAGE as 58, 69, and 74 kD. A stimulatory effect of these lectins was determined by their specific interaction with carbohydrate determinants because a competitive sugar (0.3 M MMP) suppressed completely lectin effect on germination. Polyvalent lectins capable of erythrocyte agglutination were also found among diffused proteins. These lectins are glycoproteins with Glu/Man carbohydrate determinants. MMP did not affect their capability of agglutination. This finding permits a conclusion that pollen grain wall contains lectins differing in their carbohydrate specificity.     

Ultrastructure and diversity of recent and fossil zona-aperturate pollen grains

A survey of recent and fossil zona-aperturate pollen grains within the angiosperms was undertaken. Zona-aperturate pollen (with complete ring-like apertures) has been evolved independently in several genera of basal angiosperm families (Nymphaeaceae, Eupomatiaceae, Annonaceae, Monimiaceae, Atherospermataceae) and monocots (Araceae, Iridaceae, Laxmanniaceae, Arecaceae, and Rapateaceae). The special case of the eudicot Limnanthes (Limnanthaceae) is discussed. New examples of recent and fossil fully zonate pollen are presented; a noteworthy new example are Scrophulariaceae, with Pedicularis; our fossil examples show affinities either to Nymphaeaceae, or Araceae, or Iridaceae, or cannot be related to an extant taxon. The zona-aperturate pollen grains differ in ornamentation and stratification mostly in the respect of the aperture areas, but sometimes also outside the aperture. The question of polarity is settled only for some taxa because of the frequent lack of tetrad observations. A ring-like aperture may divide the pollen grains in symmetric halves, or if running asymmetrically, divides the pollen grain in two more or less unequal halves; the presence of clearly unequal halves gives a strong argument to assume an equatorial ring in such cases where tetrad configurations were not available. The zona-aperturate condition may be a functional benefit in wet environments: while in dry pollen the apertural ring is completely closed, in wet or very moist realm it expands greatly, and the pollen tube can be formed quickly and everywhere in this area.     

Differentiating pollen of Betula species from Iceland

Subfossil pollen from two co‐existing Betula species in Iceland, B. nana and B. pubescens, is frequently found in sediments and peat. Interpretation of the findings often depends on the ability to differentiate between the two species according to pollen size and structure. Fresh pollen samples were prepared from 70 individual trees/shrubs which had been identified to species by chromosome number. Grain diameters and pore depths were measured and ratios of grain diameter to pore depth (D/P ratios) were calculated. The mean grain diameters of pollen from diploid B. nana and tetraploid B. pubescens were 20.42 and 24.20?µm, whereas mean pore depths were 2.20 and 2.81?µm respectively. Mean D/P ratios were therefore 9.55 for B. nana and 8.85 for B. pubescens. The difference between species was statistically significant for all three pollen parameters. Grain diameter appeared to be the most useful parameter, as only about 20% of the samples were in the overlapping region of the species distributions. Pollen size (grain diameter) was also positively correlated to tree morphology, which was evaluated using species‐specific botanical characters. Pollen samples from different locations/populations in Iceland varied slightly in mean size and ratio. The size difference between pollen of B. nana and B. pubescens in this study is less than other papers have reported, which may be due to the effect of introgressive hybridisation between the two birch species in Iceland.     

Effects of soil phosphorus on pollen production,pollen size,pollen phosphorus content,and the ability to sire seeds in Cucurbita pepo (Cucurbitaceae)

To determine the effects of soil phosphorus on pollen production, pollen grain size, phosphate concentration per pollen grain, and the siring ability of pollen, two cultivars of the common zucchini (Cucurbita pepo) were grown under two soil phosphorus conditions in an experimental garden. Overall, soil phosphorus availability had a significant effect on reproductive output through the female function and on traits affecting the male function of plants (staminate flower production, pollen production per flower, and pollen grain size). In addition, pollen produced by plants in the high phosphorus soils had a higher phosphate concentration than pollen produced by plants in the low phosphorus soils. A pollen mixture experiment revealed that pollen produced by plants in the high phosphorus treatment sired significantly more seeds than pollen produced by plants in the low phosphorus treatment. This study showed that growing conditions such as soil phosphorus can influence the size of a pollen grain and its chemical composition, which, in turn, can affect its ability to sire mature seeds.