Localization of pectins in the pollen tube wall of Ornithogalum virens L. Does the pattern of pectin distribution depend on the growth rate of the pollen tube?

Monoclonal antibodies that recognize pectins were used for the localization of esterified (JIM7) and acidic, unesterified (JIM5) forms of pectin in pollen tube walls of Ornithogalum virens L. (x = n = 3). The results indicated that the distribution of the two forms of pectin in the pollen tube wall depended on the medium (liquid or solid) used for pollen germination. In pollen tubes grown in the liquid medium, the localization of JIM7 was limited to the very tip of the pollen tube, whereas the localization of JIM5 indicated a uniform distribution of unesterified pectins in the very tip of the tube and along the subapical parts of the tube wall. In tubes germinated on the medium stabilized with agar (1–2%) the localization of JIM7 and JIM5 indicated the presence of both forms of pectin in the tube tip and along the whole length of the pollen tube wall in a ring-like pattern. Thus, the localization of esterified pectins in the sub-apical part of the pollen tube wall, below the apex of the tube, is described for the first time. Measurements of the growth rates of pollen tubes growing on the two types of medium indicated that oscillations in tube growth rate occur but these do not coincide with the pattern of pectin distribution in the tube wall. Our results complement the previous data obtained for the localization of JIM5 and JIM7 in pollen tube walls of other plant species. (Y.-Q. Li et al. 1994, Sex Plant Reprod 7: 145–150) and provide new insight into an understanding of the construction of the pollen tube wall and the physiology of pollen grain germination. Received: 25 January 1999 / Accepted: 23 June 1999     

Does pollen competition reduce the cost of inbreeding?

We hypothesize that floral features promoting pollen competition in angiosperms may have evolved, in some cases, in response to selection generated by the negative effects of inbreeding, at least in plants with mixed-mating systems. Screening of haploid genotypes through pollen competition may purge recessive (or additive) deleterious alleles that are expressed in haploid pollen and hence may reduce the fitness cost of self-pollination, geitonogamy, or biparental inbreeding. We tested one prediction of this hypothesis, that offspring produced by more intense competition among self-pollen have higher fitness than offspring produced by less intense competition. Dalechampia scandens (Euphorbiaceae) flowers were pollinated with pollen from other flowers on the same plant (geitonogamous self-fertilization). Those flowers experiencing more intense pollen competition as a result of low pollen dispersion (positional variance) on the stigma produced heavier seeds and seedlings with faster-growing radicles than flowers experiencing less intense pollen competition (high pollen dispersion), as predicted by our hypothesis.     

Airborne pollen flora of Jabalur – the central India

The fortnightly aerobiological survey of pollengrains at five different sites at two differentheights (ground level and at 10 m) was carriedout at Jabalpur city during January toDecember, 1996. Air sampling was done for 30minutes at each sampling point by using aRotorod air sampler. A total of 84 pollen typesbelonging to 34 families of Angiospermae andone family of Gymnospermae were identified. Themaximum mean concentration (1.04/m³ air) ofpollen was contributed by Asteraceae followedby Amaranthaceae/Chenopodiaceae (0.77/m³ air)and the minimum (0.001/m³ air) byCucurbitaceae, Convolvulaceae and Sapotaceae.Maximum numbers of pollen grains werecontributed by herb species (62.07%) followedby shrubs (18.47%) and trees (14.96%). Asmall fraction, i.e., 4.50% of total pollenflora remained unidentified. Morphologicalanalysis revealed maximum concentration(1.81/m³) of triporate pollen grains. There wasa significant difference in the pollenconcentration at ground level and at 10 mheight. The ratio observed was 1.7 : 1.0.There was non-significant negative correlation(r = –0.196) between mean pollen concentrationand mean atmospheric temperature. May, thehottest month, showed minimum mean pollenconcentration (1.65/m³ air), whereas October,with moderate temperature, the maximum(10.86/m³ air).     

Forecasting the start of <Emphasis Type="Italic">Quercus</Emphasis> pollen season using several methods – the evaluation of their efficiency

Forecasting the time when the atmospheric pollen season of allergenic plants begins is particularly important for doctors and their patients. The aim of this paper is to determine whether it is possible to forecast the start of the oak (Quercus) pollen season in Rzeszów, Poland. In the elaboration of the most effective model, various forecasting techniques were tested: growth degree days (GDD°C); meteorological factors; bioclimatic factors; and indicator taxon. The aerobiological monitoring was carried out in 1997–2005 and 2007 in Rzeszów (SE Poland). In the presented investigation, three methods defining the start of the Quercus pollen season were selected on the basis of accumulated sums of pollen or the constant occurrence of pollen grains in air. Despite the application of different combinations of GDD°C methods and threshold temperatures, the correlation coefficients between the expected and obtained values were low. In some cases, however, they proved highly effective for the test years (2005, 2007) with the accuracy of a few days. For GDD°C methods, the best threshold temperatures range between 5 and 6°C. Models based on bioclimatic indices and meteorological variables were not satisfactory. On the basic of the 10 years of results, the method of indicator species were good for forecast the start of oak pollen season. Birch was the best indicator taxa.     

Does a lateral gradient of membrane potential on the plasma membrane of growing pollen tube of germinating pollen grain exist?

The data presented in the article by Breigina et al. (2009) "Changes in the membrane potential during pollen grain germination and pollen tube growth" (Tsitologiya. 51 (10): 815-823) and concerning the measurement of electric membrane potential (Delta Psi) on the plasma membrane of growing pollen tube of germinating pollen grain with the use of fluorescent potential-sensitive dye, di-4-ANEPPS, were critically analyzed in order to clarify whether a lateral gradient of Delta Psi on this membrane indeed exists. This analysis showed that the main conclusion of the authors of the above article on the existence of polar distribution of Delta Psi along the pollen tube plasma membrane is not in accordance with a number of known peculiarities of di-4-ANEPPS behavior in biological membranes and requires a significant revision. The findings in question reported by the authors, in my opinion, might be interpreted as evidence for the presence on the plasma membrane of growing pollen tube not only the membrane potential Delta Psi but also lateral gradient of so called intra-membrane dipole potential. Based on the comments made, another interpretation of the experimental results described by Breigina et al. has been offered. In addition, some drawbacks in the methodology used by the authors for measurement of Delta Psi with other fluorescent potential-sensitive dye, DiBAC3(3), are also shortly considered.     

May the definition of pollen season influence aerobiological results?

This paper reviews the terms and major criteria used to define and limit the pollen season. Pollen data from Cordoba (Spain), Ourense (Spain) and Bologna (Italy) were used to ascertain the extent to which aerobiological results and pollen curves are modified by the criteria selected. Results were analysed using Spearmanȁ9s correlation test. Phenological observations were also used to determine synchronization between pollen curves and plant phenology. The criteria for limiting the shortest and longest pollen season periods, as well as the earliest and latest start and end dates, varied according to the city and the taxon under study; in many cases, results for a given taxon also depended on the year. The smallest differences were obtained for Platanus and the greatest for Poaceae.     

Air and surface soil samples – two different pairs of shoes? Comparing the pollen spectrum on different days of the pollen season

The pollen spectra of air and surface soil samples from a rooftop (at 14 m) and from ground level (at 1.6 m) in the suburbs of Vienna (Austria) were compared. Two soil samples and two air samples were taken on four different days to account for possible differences: in winter when no pollination occurred (reference day), in spring during the main flowering of Betula (birch day), in spring/summer during the main flowering of Poaceae (grass day), and in autumn during the main flowering of Ambrosia (ragweed day). Thirty-five different pollen types were used to describe the pollen spectra. Frequencies of certain pollen types reflect a seasonal impact on both the surface soil and air samples and show a similarity between air and soil samples on most of the days. However, the seasonal impact is higher in the air samples and shows a high consistency for ground and rooftop level. Kendall’s tau correlation coefficients further substantiate the similarities of the samples especially for the pollen season days. Exceptions include the winter day when pollination was low and the air samples recorded nearly no pollen at all, and the ragweed day when Ambrosia pollen was abundant in three of four samples but not in the ground surface soil sample. Thus, (1) air and surface pollen samples record similar signals during the pollen season but not during the ragweed and winter season and (2) air and surface pollen samples show the impact of local vegetation also in pollen traps located at different heights.     

Forecasting the start of the pollen season of Poaceæ: evaluation of some methods based on meteorological factors

The pollen of anemogamous plants is responsible for half the allergic diseases, that is to say a prevalence of 10% in the French population. Poaceæ produce the first allergenic pollen almost everywhere. The work described in this article aimed to validate forecast methods for the use of physicians and allergic people who need accurate and early information on the first appearance of pollen in the air. The methods were based on meteorological parameters, mainly temperature. Four volumetric Hirst traps were used from 1995 to 1998, situated in two departments of Burgundy. Two of the methods tested proved to be of particular interest: the sum of the temperatures and the sum of Q ₁₀ values, an agrometeorological coefficient integrating temperature. A multiple regression, using maximum temperature and rainfall, was also performed but it gave slightly less accurate results. A χ ²-test was then used to compare the accuracy of the three methods. It was found that the date of onset of the pollen season could be predicted early enough to be useful in medical practice. Results were verified in 1999, and the research must be continued to obtain better statistical validity.     

Climate change and its impact on birch pollen quantities and the start of the pollen season an example from Switzerland for the period 1969–2006

As published by the Intergovernmental Panel on Climate Change (IPCC) global warming is a reality and its impact is huge like the increase of extreme weather events, glacier recession, sea level rise and also effects on human health. Among them allergies to airborne pollen might increase or change in pattern due to the invasion of new allergic plants or due to different behavior of plants like earlier flowering. In this study we used the longest Swiss airborne pollen data set to examine the influence of the temperature increase on the time of flowering. In the case of Basel, where pollen data for 38 years are available, it was shown that due to a temperature increase the start of flowering in the case of birch occurred about 15 days earlier. Apart from a shift of the start of the flowering there is also a trend towards higher annual birch pollen quantities and an increase of the highest daily mean pollen concentrations. Due to global warming and because symptoms may appear earlier in the year people suffering from a pollen allergy might face a new unaccustomed situation.     

A practical approximation of pollen dispersal–deposition for calculation of pollen productivity and quantification of vegetation

We compared simple mathematical pollen dispersal–deposition models with Gaussian plume models. The simple mathematical models proved equal or better approximations of real world pollen dispersal–deposition. We concluded that for most standard applications, such as estimating pollen productivity or quantitative vegetation reconstructions, simple mathematical models would perform satisfactory. Such easy-to-use models may lower the threshold to employ quantitative tools to palaeoecological questions.     

Histoenzymological compartmentation of β-glucuronidase in the germinating pollen grains ofPortulaca grandiflora

The contribution deals with the distribution of β-glucuronidase in the germinating pollen grains ofPortulaca grandiflora. In non-germinating pollen grains the enzyme is localized in the pollen wall; the cytoplasmic activity is subdued. With the initiation of germination, the activity of enzyme increases and the positive granules are richly packed in the pollen grains and pollen tubes. The stigma hairs also have such an activity. The functions of the enzyme in the metabolism of germinating pollen grains are discussed.     

Monitoring of <Emphasis Type="Italic">Ambrosia</Emphasis> pollen concentration in the atmosphere of Bratislava (Slovakia) during years 2002–2007

Ambrosia pollen represents a significant allergenic risk for pollen-sensitive people also in Slovakia. The aim of this study was to compare the results of the monitoring of Ambrosia pollen concentrations and pollen seasons in Bratislava during years 2002–2007. Measurements were performed by the volumetric method using Burkard volumetric spore trap at the height of 10 m above ground level. During six monitored years, a total of 11,334 Ambrosia pollen grains per cubic meter of air were recorded. The highest total ragweed pollen amount was detected in 2002 (2,577 pollen grains of the total annual pollen concentration) and the lowest ragweed pollen concentration (1,213 pollen grains) was determined in 2007. However, mentioned year was represented as the year with the longest pollen season among the all monitored years in Bratislava (41 days). The pollen season peak day of 2002, 2004, 2005 and 2006 was recorded at the beginning of September; in 2003 and 2007 the peak was at the second half of August. The highest daily amount of Ambrosia pollen grains (more than 100 grains per cubic meter of air) was in 2002 (12 days). The results can be utilized to help to prevent symptoms of allergic reactions to Ambrosia pollen and improve quality of life during seasonal allergic diseases in ragweed pollen-sensitive people.     

Transmission of chromosomes through the eggs and pollen of triticale × wheat F1 hybrids

Summary The substitution patterns of rye chromosomes in hexaploid triticale × wheat F₂ hybrids, along with the transmission patterns of rye chromosomes through egg cells and pollen when several of the F₁ hybrids were test crossed to triticale and wheat were investigated. The data indicated that the rye chromosome transmission through both the egg and pollen was random in number and in composition. The test crosses suggested that it was best to use wheat pollen for the transmission of rye chromosomes through the egg cells of the F₁ hybrids and triticale egg cells for the transmission of rye chromosomes through F₁ hybrid pollen. A deviation from random segregation in the F₂ and the transmission rate was observed for rye chromosomes 1R, 4R/7R, and 6R. The transmission rates of 1R and 6R varied depending on the direction in which the cross was made. The results also indicated that there was little or no compensation between the R- and D-genomes and that the chromosomes of these two genomes appeared to be transmitted independently of each other.     

How to prepare a pollen calendar for forecasting daily pollen concentrations of <Emphasis Type="Italic">Ambrosia,Betula</Emphasis> and Poaceae?

Forecasting daily airborne pollen concentrations is of great importance for management of seasonal allergies. This paper explores the performance of the pollen calendar as the most basic observation-oriented model for predicting daily concentrations of airborne Ambrosia, Betula and Poaceae pollen. Pollen calendars were calculated as the mean or median value of pollen concentrations on the same date in previous years of the available historic dataset, as well as the mean or median value of pollen concentrations of the smoothed dataset, pre-processed using moving mean and moving median. The performance of the models was evaluated by comparing forecasted to measured pollen concentrations at both daily and 10-day-average resolutions. This research demonstrates that the interpolation of missing data and pre-processing of the calibration dataset yields lower prediction errors. The increase in the number of calibration years corresponds to an improvement in the performance of the calendars in predicting daily pollen concentrations. However, the most significant improvement was obtained using four calibration years. The calendar models correspond well to the shape of the pollen curve. It was also found that daily resolution instead of 10-day averages adds to their value by emphasising variability in pollen exposure, which is important for personal assessment of dose-response for pollen-sensitive individuals.     

Does pollen availability mitigate the impact of pesticides on generalist predatory mites?

The effect of the provision of pollen on the impact of pesticides on the predatory mite Kampimodromus aberrans was assessed at individual and population levels. In the laboratory we evaluated the influence of pollen amount and pollen application frequency on lethal and sub-lethal effects of chlorpyrifos and spinosad. In a potted plant experiment, the effects of pesticides and pollen were assessed on predatory mite population abundance. In the laboratory, survival and fecundity of predatory mites were reduced by insecticides, and spinosad was more toxic than chlorpyrifos. In the same experiment, high pollen application frequency alleviated the sub-lethal effect induced by chlorpyrifos. On potted plants, pollen applications reduced the impact of chlorpyrifos on K. aberrans, whereas without pollen applications the impact of spinosad and chlorpyrifos on the predatory mite population was similar. Results obtained here highlight that the provision of fresh pollen is of particular importance for predatory mites when pesticides are applied.     

Geospatial analysis of pollen records from the Yucatán peninsula, Mexico

Changes in distribution of semi-evergreen forest in the Yucatán peninsula and variation of precipitation during the late Holocene were inferred using a geographical information system. Deterministic methods for spatial interpolation using fossil pollen data from seven cores elucidated environmental changes. The changes in the distribution of the semi-evergreen forest allowed to us infer variations in precipitation in the area and to distinguish whether changes of forest cover are a consequence of climate and/or of human activities. The reconstruction of the Preclassic period (at 550 and 50 b.c.) indicates higher precipitation than at present and suggests a more closed vegetation cover. Around a.d. 450 the vegetation acquired an open character indicating a reduction in precipitation. During this time the decrease in forest was not homogeneous in the Yucatán peninsula, indicating human impacts in certain areas. A reduction in forest cover but not a complete deforestation of the region is assessed during the Classic period (a.d. 450). The reconstruction of a.d. 950 shows the recovery of the forest and is related to the Medieval warm period. Geographical information systems are useful tools to reconstruct the spatial history of the vegetation of the Yucatán peninsula during the late Holocene.     

The role of Cl<Superscript>−</Superscript> in pollen germination and tube growth

The involvement of Cl^? in cytoplasm polarization in the pollen tube and membrane potential control during pollen germination in vitro was studied by fluorescence techniques in Nicotiana tabacum. Cl^? release from cells was blocked by the anion channel inhibitor nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) or by the addition of Cl^? to the incubation medium. The concentrations of the inhibitor (40 μM) and extracellular Cl^? completely inhibiting pollen germination (200 mM) and pollen tube growth (100 mM) were used. The release of anions from the pollen grain has been revealed in the first minutes of hydration also in the presence of 200 mM Cl^?. The inhibitor blocked this process completely, which points to the significance of the NPPB-sensitive anion channels in the transmembrane Cl^? transport at the early activation stage. The pollen tube membrane was hyperpolarized in the presence of 100 mM Cl^?; however, exogenous Cl^? had no effect on the compartmentalization and organelle movement in the tube. The inhibitor depolarized the plasma membrane in the pollen grain and tube and affected the polar organization of the cytoplasm and organelle movement. Thus, activity of NPPB-sensitive chloride channels was required to regulate the potential on the plasma membrane and to maintain the functional compartmentalization of the cytoplasm, which provides for the polar growth.     

Annual variation of airborne pollen in the city of Palencia,Spain, 1990–1992

The aim of this work is to present the atmospheric pollen concentrations of Palencia, Spain. Data were collected for three consecutive years (1990–92). An active volumetric pollen trap, type CAP2, was used. During this time, 88 different pollen types were identified, of which 27 occured at more than 0.15% of the total pollen recorded annually. These types formed the main pollen spectrum of this sampling station. Pollen coming from herbs (Poaceae, Chenopodiaceae, Plantago Urticaceae, etc.) was predominant (53.79%); arboreal pollen (Quercus, Populus Cupressaceae, etc.) represented 42.11%, and pollen from shrubs (Ericaceae, Sambucus etc.) only 4.10%.

May and June was the time of the year with maximum pollen emission to the air. This was due to the quantities of pollen coming from Poaceae and Quercus which together represent 47.25% of the pollen recorded over the three‐year sampling period. Herbaceous pollen appeared throughout the year with maximum concentrations recorded in the spring, coinciding with the maximum levels of arboreal pollen in the atmosphere.

An analysis of multiple regression and one‐way anova test between pollen concentrations and selected meteorological parameters show that relative humidity and average temperature are the meteorological factors most correlated with the concentrations of specific pollen types (Plantago, Ligustrum, Sambucus, Carex). In the same way, when the winds are predominantly from the northeast (second quadrant), there are higher pollen concentrations of Sambucus Ericaceae and Mercurialis.     

<Emphasis Type="BoldItalic">Betula</Emphasis> spp. pollen in the atmosphere of Novi Sad (2000–2002)

Pollen of Betula spp. is one of the main European aeroallergens. The aim of this study was to determine characteristics and occurrence of the Betula pollen in Novi Sad atmosphere, based on 3-year observations (2000–2002), and to compare pollen season start dates calculated by different methods. Pollen samples have been collected by Hirst volumetric method with a 7-day Burkard spore trap. Four methods (Sum 75, 2.5%, 30 and 1 pg/m ³) have been used for determination of the start dates of the Betula pollen season and the results have been compared. The total annual pollen sum increased during the observed period. In 2000, 2001 and 2002, the highest daily pollen concentrations were 97, 137 and 1034 pg/m ³, respectively. The earliest Betula pollen season start has been calculated by the 1 pg/m ³ method.     

Poaceae pollen in the atmosphere of Zagreb (Croatia), 2002 – 2005

Pollen of grasses (Poaceae) is one of the most important airborne allergen sources worldwide. The aim of the study was to determine diurnal, day‐to‐day, weekly, monthly and annual pollen variation, and the effect of selected meteorological parameters on atmospheric pollen concentrations in Zagreb. A preliminary study was carried out during four seasons (2002 – 2005), using a 7‐day VPPS 2000 Hirst volumetric pollen trap. Total annual grass pollen concentrations in Zagreb were constant (2 673 – 3 074 p.g.m^?3), with a relative drop in 2004 (1 196 p.g.m^?3). The beginning of the grass pollen season is usually observed when the average daily temperature exceeds 13.5°C (max. daily temp. 19.5°C), without precipitation. In all four study years the absolute peak of concentrations occurs in the second half of May. The length of pollen season during the study period was 157 – 173 days. A high variability was observed in the maximal concentration and in the number of days when grass pollen concentration exceeded the threshold value of 30 p.g.m^?3 (9 – 40 days). Statistically significant correlations were found between airborne grass pollen concentrations and air temperature, level of precipitation and relative humidity.