Total Pollen Grains Research Articles

THE POLLEN CALENDAR OF THE EMIRGAN GROVE, ISTANBUL (TURKEY)

Pollen calendars created for residential areas play a vital role in protecting and treating the sufferers of allergic diseases. In this regard, gravimetric and volumetric pollen traps are placed in the city and town centers. In the process of creating the Emirgan Grove’s pollen calendar, the gravimetric method was utilized together with the Durham sampler between March and September 2020. During this seasonal year, a total of 13464 pollen grains were recorded. According to the obtained pollen analysis results, the pollen grains of 44 taxa including 32 arboreal and 12 non-arboreal taxa were determined. Total pollen grains consisted of 90.95 % grains from arboreal plants, 9.05 % grains from non-arboreal plants. The period with the highest amount of pollen was detected as April. The taxon with the highest pollen concentration was Pinus. In terms of pollen concentrations, Pinus was followed by Cupressaceae, Tilia, Abies, Poaceae, Prunus, Morus and Quercus respectively. This study has been the first pollen calendar study conducted for groves and parks in Turkey.

Elm pollen concentrations in the atmospheric air of selected Polish cities in 2022

The elm (Ulmus sp.) is one of the early spring flowering trees. The aim of the study was to compare the elm pollen season in selected Polish cities in 2022. The aeropalynological measurements were carried out with the volumetric method. The study was focused on determination of the total daily pollen grain concentrations during the season, the beginning and end of the pollen season (determined using the 95% method), the peak pollen concentrations, and the dates with maximum pollen concentrations. The earliest onset of the elm pollen season was noted in Sosnowiec (March 9th). In turn, the latest onset was recorded in Lublin (March 23th). The pollen season lasted from 18 days (in Cracow) to 37 days (in Sosnowiec). The highest total daily pollen grain concentrations and the highest maximum concentration were recorded in Cracow (1202 and 321 P/m3, respectively), whereas the lowest values of these parameters were noted in Bialystok (72 and 9 P/m3, respectively). In most of the analyzed cities, the peak pollen concentration was recorded between March 25th and 29th.

Identification of the Main Phenolic Markers in Turkish Pine Honeys and Their Biological Functions.

The purpose of this research was to identify the biological activity of Turkish pine honeys and the most abundant phenolic compound(s) to guide future studies to be done about this type of honey. Moreover, this will provide the chance to introduce Turkish pine honeys by elucidating a distinct parameter compared to other forms of honey reported in the literature. To this end, microscopic examination based on the number of honeydew elements (NHE) and the number of total pollen (NTP) grains was performed on 17 samples of pine honeys from the Aegean region of Turkey. Then 18 commonly-occurring phenolic standards were used in high-performance liquid chromatography (HPLC) to examine the samples. Each sample was tested for individual phenolic compounds, as well as total phenolic content (TPC), total flavonoid content (TFC), and ferric reducing antioxidant power (FRAP). As shown by the numerical data, the values for NHE and NTP were 6600-144000 and 3000-75000, respectively. In addition, the general means of TPC, TFC, and FRAP values for the samples were 53.000 mg GAE/100 g fresh sample, 1.944 mg QE/100 g fresh sample, and 3.455 μmol FeSO4 /g fresh sample, respectively. Protocatechuic acid predominated with a range of 197.841-780.227 μg phenolic /100 g sample in all samples. According to the general mean for values detected in the samples, p-hydroxybenzoic acid and benzoic acid were the second and third markers for Turkish pine honey samples. It is believed that these results will help efforts to set standards for pine honey on a national and global scale.

The influence of self-pollen deposition on female reproductive success in a self-incompatible plant, Akebia quinata.

Geitonogamy is inevitable in hermaphrodite and monecious. Even for self-incompatible species, the negative effects of self-pollen are unavoidable when geitonogamous or self-mating occurs. However, the influence of self-pollen on consecutive development of flowers (e.g., fruiting and seeding) was seldom evaluated. Here, the self-incompatible monecious species, Akebia quinata, was used to estimate the influence of self-pollen deposition. We evaluated the extent of pollen limitation and geitonogamous mating under natural conditions by count of stigmatic pollen load and pollen tracking experiment. Hand pollination with different amount and combinations of self vs. cross pollen grains was applied to detect the response of fruit and seed set. The results showed that geitonogamy and pollen limitation occurred under natural conditions in A. quinata. Carpel numbers, ratio of self- and cross-pollen, and the interactive effect of ratio of self- and cross-pollen and total mixed pollen numbers, and not total pollen grain number, determined the effect of self-pollen on female reproductive success. The effect of self-pollen depended on its intensity. In general, the transfer of self-pollen significantly affected young fruit set. However, a little self-pollen together with cross-pollen did not reduce young fruit production. Although self-incompatible plants have evolved physiological mechanisms that reduce self-fertilization, our results provide new insights into the effects of self-pollen and the adaptive significance of self-incompatible monecious species.

How panicle angle and panicle position in the canopy determine pollination and seed set in rice (Oryza sativa L.)

ABSTRACT We examined the effect of panicle position relative to canopy and of panicle angle on pollination and floret sterility in rice at anthesis in a paddy field. We set panicles of pot-grown rice at the flowering stage either upright (0°) or inclined (30°), either above or at canopy height (Experiment 1) and either beneath or at canopy height (Experiment 2), in three replications each. In Experiment 1 and Experiment 2, panicle inclination at 30° increased the percentage of florets with <20 total pollen grains on the stigma (TP20) by 21% and 27%, increased the percentage of florets with <10 germinated pollen grains on the stigma (GP10) by 21% and 30%, and increased floret sterility by 10% and 26%, respectively. Floret sterility was correlated with GP10 in all trials. GP10 was correlated with TP20. The effect of position on floret sterility was not significant. We conclude that panicle inclination at 30° significantly increased floret sterility even under the canopy condition. Uprightness of panicles should be an important objective in rice breeding and production. Abbreviations TP20, percentage of florets with <20 total pollen grains on the stigma; GP10, percentage of florets with <10 germinated pollen grains on the stigma.

Dependence of pollination and fertilization in rice (Oryza sativa L.) on floret height within the canopy

We examined changes in rice (Oryza sativa L.) floret sterility and pollination as a function of vertical position of florets in the canopy at anthesis in paddy fields to clarify the ideal panicle height. Flowering pot-grown rice plants were placed in the rice canopy at different heights to position their florets at different depths below the canopy surface. The percentage of floret sterility was approximated as Y = 0.000335 X12 + 0.0296 X1 – 0.0451 X2 + 0.0152 X1X2 – 0.0468 (R2 = 0.921), where Y is the logit-transformed floret sterility (%), X1 is floret depth at anthesis (cm), and X2 is wind speed above the canopy (m s–1). The percentage of florets with fewer than 20 pollen grains on the stigma after flowering was approximated well by Y = 0.000554 X12 – 0.235 X22 + 0.5346 (R2 = 0.892), where Y is the logit-transformed percentage. The floret sterility (%) was correlated with the percentage of florets with <10 germinated pollen grains and with the percentage with <20 total pollen grains. Thus, there exists an optimal flowering depth and an ideal panicle position with respect to the canopy surface that stabilizes pollination and fertilization, and the optimal position for fertilization deepens with increasing wind strength.

Panicle inclination influences pollination stability of rice (Oryza sativa L.)

ABSTRACTRice pollination occurs when pollen grains fall by gravity from the anther onto the stigma and has been thought to be assured under suitable conditions. However, the position of the stigma relative to the anther pores may affect pollination. The inclination of panicle, that is quite usual in agricultural scene, may change the relative position of anther and stigma. We investigated the effect of panicle inclination on pollination stability. Pots of rice at flowering stage were tilted at one of the four inclinations (0° = control, 15°, 30°, and 45°). We assessed pollination (numbers of total and germinated pollen grains on the stigma) and morphology of dehisced anthers. Inclination significantly affected the number of total and germinated pollen grains on the stigma: as it increased from 0° to 45°, the percentage of florets with <20 total pollen grains on the stigma (TP20) increased from 36.6% to 59.9%, and that of florets with <10 germinated pollen grains on the stigma (GP10) increased from 26.6% to 58.9%. Both an increase in TP20 and a decrease in the rate of pollen germination were major causes of the increase in GP10. Inclination did not affect anther morphology. A panicle inclination of ≥30°could greatly reduce rice production because rice fertilization requires >10 germinated pollen grains on the stigma. Uprightness of the panicle at flowering should be an important objective in rice breeding and production.Abbreviations: TP20: percentage of florets with <20 total pollen grains on the stigma; GP10: percentage of florets with <10 germinated pollen grains on the stigma

Pruned petioles of papaya as nesting sites of the leafcutting bee, Megachile laticeps Smith and its pollen fidelity

The nest selection and pollen fidelity of the leafcutting bee, Megachile laticeps was studied. Mature and nearly dry petioles of papaya were pruned to simulate hollow stems of other plants to attract females of M. laticeps for construction of its nest. The nest occupancy and adult emergence rate were 64.70% and 89.07% respectively, with an average of 12.7 ± 2.11 cells per nest. Scopal pollen loads from foraging adult female bees were removed and identified to the lowest taxonomic level possible. Pigeon pea, sunnhemp, and field bean pollen (Fabaceae) made up on an average of 54% of total pollen grains carried in the scopae of adult female bees. Nest pollen analysis indicated that Fabaceae pollen was the most prevalent in the brood provision. M. laticeps in a farm landscape utilized the pruned hollow petioles of standing papaya plant and local floral resources. This behavior shows the importance of pollinator species’ characteristics for developing conservation strategies to enhance pollination services in agro-ecosystems.

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

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.

Do Conocarpus erectus airborne pollen grains exacerbate autumnal thunderstorm asthma attacks in Ahvaz, Iran?

A disastrous outbreak of thunderstorm-induced asthma attacks posed a major public health threat in Ahvaz, Iran in autumn of 2013 (>15,000 referrals to hospital emergency rooms and pulmonary clinics). City officials claimed that promoting factors included acid rain, particulate matter, ozone, and polycyclic aromatic hydrocarbon compounds (PAHS) could lead to this phenomenon. After these potential causes were rejected by careful research, the next possible cause that this study addresses is a potential link of the asthma attacks to airborne pollen grains and fungal spores. In order to sample these parameters, a Hirst-type volumetric spore sampler was used, which was installed on the rooftop of the sampling site. Sampling was done during two six-month periods to characterize the regional bioaerosol. The first period included the autumn (September 22 to December 20 of 2016) and winter seasons (December 21 of 2016 to March 19 of 2017), while the second period included the following autumn (September 23 to December 21 of 2017) and winter seasons (December 22 of 2017 to March 20 of 2018). In both studied periods, airborne weed pollen grains, especially Amaranthaceae sp., were by far the greatest contributor to total airborne pollen grain concentrations (50.45%, 3757 pollen grains/m3 and 52.12%, 2392 pollen grains/m3, respectively). Among fungal spores, Cladosporium had the highest concentrations (75.29%, 258677 spores/m3 and 80.33%, 247693 spores/m3, respectively). Findings also showed that concentrations of airborne pollen grains were higher in autumn seasons (6361 and 4167 pollen grains/m3, respectively) in comparison with winter seasons (1085 and 423 pollen grains/m3, respectively), while the concentrations of fungal spores were enhanced in winter seasons (189216 and 160962 spores/m3, respectively) versus autumn seasons (154377 and 147377 spores/m3, respectively). Fungal spores exhibited a uniform distribution during the entire study period, but airborne pollen grains were significantly higher in autumn seasons. The numbers of referrals associated with thunderstorm asthma attacks decreased drastically after implementing Conocarpus erectus tree pruning activities. We concluded that the autumnal thunderstorm asthma attacks in Ahvaz might be triggered by a combination of bio-allergens (fungal spores and airborne pollen grains such as from Conocarpus erectus) and high levels of air pollutants from industrial activity. The results of this work suggest controlling bio-allergen levels by preventive measures such as tree pruning, weed removal, and emasculating urban green infrastructures before the flowering season.

Temporal Variability and Geographical Origins of Airborne Pollen Grains Concentrations from 2015 to 2018 at Saclay, France

The study of the origin and dispersion processes associated with airborne pollen grains are important to understand due to their impacts on health. In this context, a Hirst-type spore trap was utilized over the period 2015–2018 to monitor ambient pollen grains at Saclay, France, a receptor site influenced by both clean air masses originating from the Atlantic Ocean and polluted air masses under anticyclonic conditions. The objective of this work was to use ZeFir (a user-friendly, software tool recently-developed to investigate the geographical origin and point sources of atmospheric pollution) as a method to analyse total and allergenic airborne pollen grain concentrations. Strong interannual variability was exhibited for the total pollen grains concentrations and it was determined that this was mainly driven by Betulaceae pollen, with a general increasing trend displayed. The start of the pollen season was seen to be triggered by particular synoptic conditions after a period of dormancy and two maximums were displayed, one in April and a second in June. Results from the ZeFir tool, fed with on-site hourly meteorological and pollen measurements, demonstrate that the dominant pollen grains inputs to Saclay are favoured by non-prevailing winds originating from East and North in association with dry air, moderate winds, mild temperature and enhanced insolation.

ANALYSIS OF ATMOSPHERIC POLLEN GRAINS IN DURSUNBEY (BALIKESİR), TURKEY

In this study, airborne pollen grains in the atmosphere of Dursunbey (Balıkesir, Turkey) were collected using a gravimetric method. The pollen grains were investigated by light microscopy and a total of 6265 pollen grains per cm2 were counted. 42 different pollen types were identified of which 24 belonged to the arboreal plants (86.17% of the annual pollen index) and 18 to non-arboreal plants (13.16% of the annual pollen index). A small portion of the pollens (42 grains, 0.67%) were not identified. The most frequent pollen types, which constituted more than 1% of annual pollen count were regarded as the predominating pollen types for the region. The predominating group was determined to be consisted of pollens of Pinus L. (48.23%), Cupressaceae Rich. ex Bartl./Taxaceae Gray (16.74%), Poaceae Barnhart (8.32%), Quercus L.(5.31%), Acer L. (4.07%), Platanus L. (3.10%), Juglans L. (2.26%), Abies Mill. (1.75%), Plantago L. (1.25%), Amaranthaceae Juss. (1.22%) and Olea europaea L. (1.16%). The highest pollen count was determined in May and it is striking that most of the determined predominant pollen types have previously been reported as main causes of pollinosis.

Native Bee Diversity and Pollen Foraging Specificity in Cultivated Highbush Blueberry (Ericaceae: Vaccinium corymbosum) in Rhode Island.

We identified 41 species of native bees from a total of 1,083 specimens collected at cultivated highbush blueberry plantings throughout Rhode Island in 2014 and 2015. Andrena spp., Bombus spp., and Xylocopa virginica (L.) were collected most often. Bombus griseocollis (DeGeer), B. impatiens Cresson, B. bimaculatus Cresson, B. perplexus Cresson, and Andrena vicina Smith collected the largest mean numbers of blueberry pollen tetrads. The largest mean percent blueberry pollen loads were carried by the miner bees Andrena bradleyi Viereck (91%), A. carolina Viereck (90%), and Colletes validus Cresson (87%). The largest mean total pollen grain loads were carried by B. griseocollis (549,844), B. impatiens (389,558), X. virginica (233,500), and B. bimaculatus (193,132). Xylocopa virginica was the fourth and fifth most commonly collected bee species in 2014 and 2015, respectively. They exhibit nectar robbing and females carried relatively low blueberry pollen loads (mean 33%). Overall, we found 10 species of bees to be the primary pollinators of blueberries in Rhode Island.

Pollination biology of Callistemon viminalis (Sol. Ex Gaertn.) G. Don (Myrtaceae), Punjab, Pakistan

A research was conducted to find out the floral traits and pollinator's community of bottle brush (Callistemon viminalis: Myrtaceae). Total numbers of pollen grains, pollen grain viability, stigma receptivity, nectar volume and nectar concentration, numbers of ovules and pollen/ovule ratio were recorded. The pollinators' abundance, visitation rate and frequency were also observed. In field experiment, capsule weight, seed setting and seed numbers in open and caged flowers were also evaluated. The results revealed a total of 128,139 pollen grains/flower. Among total pollen grains, viable pollen grains were 84.3% and non-viable were 15.69%. There were 275 ovules/flower and pollen ovule ratio was 472.50. Stigma receptivity was decreased with the age of the flowers and stigma remained receptive for about 6days. The nectar volume and nectar concentration were 13μL and 29%, respectively. The flowers were visited by nine Hymenopteran, four Lepidopteran, one Dipteran and one bird species. Among all pollinators, bees represented the most abundant species (1290) and showed the highest visitation rate (3.6–13.8 numbers of flowers/min) and visitation frequency (0.22–1.92 individuals/branch/5min). Open-pollinated flowers showed statistically higher capsule weight (0.0824±0.001), seed setting (0.052±0.0001) and seed numbers (242.4±2.87) as compared to flowers in cages.

Shortened anther–stigma distance reduces compatible pollination in two distylousPrimulaspecies

Distyly has been regarded as an adaptation to improve compatible pollination between two floral morphs with reciprocal herkogamy. The hypothesis that the different positions of anthers and stigmas within flowers as well as their reciprocal position between morphs, reduce the probability of self pollination raised by Darwin has been rarely tested. In this study, we measured stigmatic pollen loads in response to reduced reciprocal herkogamy in two Primula species. To see whether reciprocal herkogamy can increase compatible and/or reduce incompatible pollen deposition, thus promoting compatible pollination, we shortened the distance between anthers and stigmas within the flowers by changing the position of the corolla tube, to which the anthers were fused, i.e. reduced herkogamy in natural populations of Primula secundiflora and P. poissonii and quantified stigmatic pollen loads in the field over 2 years. In both species, stigmatic pollen loads were significantly higher in the long-styled (L-morph) than in the short-styled morph (S-morph) in both control and manipulated flowers, but percentage of compatible pollen in S-morph were higher. Flowers manipulated to halve the anther–stigma distance showed a similar pattern for 2 years: total pollen grain counts on stigmas did not differ significantly but compatible pollen grains in L- and S-morphs were significantly decreased in both species. The percentage of compatible pollen loads was decreased by 68.7% in P. secundiflora and 65.3% in P. poissonii in L-morphs, while it decreased by 30.6% and 2.9% in S-morphs, respectively. Our manipulation of the relative position of anthers and stigmas in the two distylous species indicated that a lower degree of herkogamy reduced compatible but incompatible pollen transfer was likely to increase. The higher proportion of compatible pollen in the S-morph than in the L-morph in the two Primula species could be attributed to the accessibility of two-level sexual organs, floral orientations and pollinator behaviors. This is a first attempt to manipulate intraflower herkogamy for understanding adaptation of heterostyly, shedding insights into how the reciprocal herkogamy promotes compatible pollination.

Cooling water before panicle initiation increases chilling-induced male sterility and disables chilling-induced expression of genes encoding OsFKBP65 and heat shock proteins in rice spikelets.

In rice (Oryza sativa L.), chilling-induced male sterility increased when plants experienced low water temperature (Tw , 18 °C for 14 d) before panicle initiation. The number of mature pollen grains after chilling at the booting stage (12 °C for 5 d) was only 45% of total pollen grains in low-Tw plants, whereas it was 71% in normal-Tw plants (Tw not controlled; approximately 23 °C under air temperature of 26 °C/21 °C, day/night). Microarray and quantitative PCR analyses showed that many stress-responsive genes (including OsFKBP65 and genes encoding the large heat shock protein OsHSP90.1, heat-stress transcription factors and many small heat shock proteins) were strongly up-regulated by chilling in normal-Tw spikelets, but were unaffected or even down-regulated by chilling in low-Tw spikelets. OsAPX2 and genes encoding some other antioxidant enzymes were also significantly down-regulated by low Tw in chilled spikelets. The levels of lipid peroxidation products (malondialdehyde equivalents) were significantly increased in low-Tw spikelets by chilling. Ascorbate peroxidase activity in chilled spikelets was significantly lower in low-Tw plants than in normal-Tw plants. Our data suggest that an OsFKBP65-related chilling response, which protects proteins from oxidative damage, is indispensable for chilling tolerance but is lost in low-Tw spikelets.

The threat of allergenic airborne trees pollen to pollinosis sufferers in a rural area (Western Pomerania, Poland)

The aim of the study was to investigate the concentration of &lt;em&gt;Alnus&lt;/em&gt; L., &lt;em&gt;Corylus&lt;/em&gt; L. and &lt;em&gt;Betula&lt;/em&gt; L. pollen in the village of Gudowo (Western Pomerania, Poland) in the years 2012–2014 in order to estimate the threat of allergenic tree pollen in this rural region. Measurements were performed using the volumetric method (VPPS Lanzoni 2000 pollen sampler). The duration of the pollen season was determined by the 98% method, taking days on which, respectively, 1% and 99% of the annual total pollen grains appeared as the beginning and end of the season. Pollen grains from hazel occurred in the air as the first ones, before pollen grains from alder and birch. The earliest beginning of the hazel pollen season was recorded in 2012, whereas alder and birch pollen seasons started the earliest in 2014. Daily maximum pollen concentrations of the investigated taxa were recorded in 2014. Birch pollen allergens posed the largest threat to pollinosis sufferers. In the years 2012–2014, pollen concentrations equal or higher than threshold values, at which people with pollinosis show allergic symptoms, were recorded most frequently for birch, hazel, and alder (25, 19, and 14 days, respectively). The highest hourly alder pollen concentration was recorded at 16:00 and in the case of hazel at 15:00. The diurnal distribution of birch pollen concentrations does not show any distinct peaks.

Pollen Collected and Foraging Activities of Frieseomelitta varia (Lepeletier) (Hymenoptera: Apidae) in an Urban Landscape

Cities provide resources for animal species that live within them or inhabit their surroundings. This has motivated an increase in ecological studies of urban areas, including the interactions between plants and pollinators. From March 2010 to February 2011, the flowering plants present in the study area, located at the Universidade de São Paulo, Ribeirão Preto, were sampled to evaluate how floral sources were distributed throughout the year. Concurrently, worker bees with pollen loads were collected from four colonies of Frieseomelitta varia (Lepeletier, 1836) to identify the sources used by bees. Despite an increase in plant species abundance in July, plants were in bloom year-round and consequently, the production and supply of floral resources were continuous. The workers collected resources from 77 plant species, but only three were extensively exploited. Delonix regia (Leguminosae), Poincianella pluviosa (Leguminosae) and Ceiba speciosa (Malvaceae) accounted for 42% of total pollen grains quantified during the year, showing that F. varia intensify pollen collection at few sources at spatiotemporal scale. This study emphasizes the importance of native urban flora to maintain F. varia and other bee species. The list of plants presented in this study can be used in the design and planning of urban areas.

A new approach for reconstruction of the Holocene climate in the Mongolian Altai: The high-resolution δ13C records of TOC and pollen complexes in Hoton-Nur Lake sediments

δ13C of total organic carbon (TOC) and pollen grain, TOC, C/N ratio, and δ15N of total organic nitrogen (TON) in a 2.57-m long core from Hoton-Nur Lake in Mongolian Altai have been measured for reconstruction of the Holocene climates. The δ13C values of TOC and pollen carbon have similar average values but different ranges. Pollen δ13C has negative correlation with %AP (arboreal taxa pollen) and positive correlation with %NAP (herbaceous pollen and spores) that are connected with conditions of humidity in the area. Taiga-biome has lighter δ13C than steppe-biome. Hence, pollen δ13C composition is more sensitive to changes of humidity in the analogous spectra than palynotaxonomical structure and δ13C of TOC. Based on our results, the Holocene climates in Mongolian Altai are: (1) dry conditions prior to 11.5kyr BP; (2) wet conditions between 11.5 and 6.0kyr BP; (3) a relatively dry/cool episode during 6–4kyr BP; (4) stable cool and semiarid conditions with moderately effective moisture during the past 4000years. Two abrupt climatic changes occurred at ∼7.45kyr BP and ∼11.5kyr BP might be related to glacial activities. The Holocene climatic trend in Mongolian Altai which is controlled by the Westerlies is similar to the trend of monsoonal climate shown by the Chinese speleothem records as well as the lake/sand dune evidence in the deserts of NW China. The contact of the two climatic systems and shift of the monsoonal boundary during the past need to be further studied.

Pollen-ovule ratios in seven species ofVaccinium(Ericaceae) and stamen structure inVaccinium myrtilloidesandVaccinium vitis-idaea1This article is part of a Special Issue entitled “Pollination biology research in Canada: Perspectives on a mutualism at different scales”.

Pollen-ovule (P/O) ratios were determined for five Vaccinium species (Ericaceae) native to eastern Canada (Nova Scotia: V. angustifolium, V. boreale, V. caespitosum, V. corymbosum, V. uliginosum), one in western Canada (Saskatchewan: V. myrtilloides), and one (V. vitis-idaea) from both provinces. Pollen, released at maturity as tetrads, was converted to total pollen grains per flower to yield P/O ratios ranging from 238 (V. caespitosum) to 2008 (V. vitis-idaea), but 736 for the latter in Saskatchewan. These P/O ratios are indicative of facultative autogamy to facultative xenogamy. Additionally, the structure of mature stamens and pollen tetrads was studied in V. myrtilloides and V. vitis-idaea. Each anther was functionally bilocular; had a single-cell thickness (i.e., epidermis) with regularly occurring papillae; lacked an endothecium; and possessed two distal, hollow tubules each terminating in a pore. Overall pollen grain viability was 76%–97% (V. myrtilloides) and 51%–93% (V. vitis-idaea), with about 20% of tetrads having only 1–3 grains viable, and 12% and 27% of tetrads entirely nonviable in V. myrtilloides and V. vitis-idaea, respectively. Pollen tetrads occasionally were connected by a sticky substance resembling pollenkitt, but viscin threads were absent. One instance of precocious (in situ) germination of tetrads was recorded within anthers of V. myrtilloides.