Mating dynamics of Scots pine in isolation tents

Seed orchards are forest tree production populations for supplying the forest industry with consistent and abundant seed crops of superior genetic quality. However, genetic quality can be severely affected by non-random mating among parents and the occurrence of background pollination. This study analyzed mating structure and background pollination in six large isolation tents established in a clonal Scots pine seed orchard in northern Sweden. The isolation tents were intended to form a physical barrier against background pollen and induce earlier flowering relative to the surrounding trees. We scored flowering phenology inside and outside the tents and tracked airborne pollen density inside and outside the seed orchard in three consecutive pollination seasons. We genotyped 5683 offspring collected from the tents and open controls using nine microsatellite loci, and assigned paternity using simple exclusion method. We found that tent trees shed pollen and exhibited maximum female receptivity approximately 1 week earlier than trees in open control. The majority of matings in tents (78.3 %) occurred at distances within two trees apart (about 5 m). Self-fertilization was relatively high (average 21.8 %) in tents without supplemental pollination (SP), but it was substantially reduced in tents with SP (average 7.7 %). Pollen contamination was low in open controls (4.8–7.1 %), and all tents remained entirely free of foreign pollen. Our study demonstrates that tent isolation is effective in blocking pollen immigration and in manipulating flowering phenology. When complimented with supplemental pollination, it could become a useful seed orchard management practice to optimize the gain and diversity of seed orchard crops.     

The pollination seesaw of Rhynchospora cephalotes (L.) Vahl (Cyperaceae): Influence of plant location on the role of wind and insects as pollen vectors

Ambophily (wind and insect pollination) has been reported for some genera of the typically wind-pollinated family Cyperaceae, including the genus Rhynchospora. The significance of wind and insect pollination can vary, depending on local microclimatic conditions. Rhynchospora cephalotes is an ambophilous species that can grow under different environmental conditions, either along forest edges or inside forest fragments. This study, therefore, tests the hypothesis that (a) there is greater contribution by wind than insects to fruit set of the individuals at the forest edge and (b) there is greater contribution by insects than wind to fruit set of the individuals inside the forest. Field work was carried out in a fragment of Atlantic Forest in northeastern Brazil. We quantified the number of visits by insects, wind velocity and the reproductive success (fruit set) of R. cephalotes provided by wind and insects through exclusion experiments performed at the edge of and inside the forest. We observed a greater number of visits per day by pollinating bees to individuals inside the forest (36.83 ± 7.46) than to individuals at the edge (16.66 ± 6.53). The wind speed was significantly higher at the edge (1.71 ± 0.46 m/s) than inside the forest (0.97 ± 0.18 m/s). Bees and wind are both pollen vectors of R. cephalotes, but bees were the pollen vector that contributed most to fruit set (63.3%) for individuals inside the forest, whereas wind was the primary vector for individuals at the forest edge (76.6%). This seesaw in importance of each pollen vector in the two different environments guarantees high fruit set in R. cephalotes under different microclimatic conditions.     

天山雪岭云杉大气花粉含量对气温变化的响应

对中国东天山天池自2001年7月至2006年7月连续5a收集的雪岭云杉大气花粉含量进行统计分析,结果表明:1)一年四季大气中都有雪岭云杉花粉,但花粉数量变化比较大,超过全年90％的大气花粉集中在5、6月份的花粉高峰期,之后花粉浓度逐渐下降,至翌年1月份浓度降至最低,2月开始花粉浓度有升高的趋势;2)5a平均花粉浓度是42.66粒/m3,最高年是2005年,花粉浓度可达99.54粒/m3,最低年2003年,仅为2.13粒/m3;3)雪岭云杉大气花粉高峰期出现在5月22至6月2日,高峰日出现在5月28至6月6日,结束日是在6月18至6月25日,平均持续时间为27 d.观测时段雪岭云杉大气花粉高峰期出现日、高峰日逐年提前,2006年出现日期比2002年提前了7d、高峰日提前9d,结束日期滞后,2006年比2002年滞后6d,花粉高峰期持续时间逐年延长,2006年比2002年延长了12d.分析显示,影响雪岭云杉大气花粉高峰期变化的主要因素是春季气温的升高;4)粗略估算每年新疆的雪岭云杉林带内由大气中降落到表土的花粉量达61 kg/hm2,新疆现有雪岭云杉52.84×104hm2,全年由大气降落到林带内表土的花粉多达3223 t,一部分降落到戈壁、荒漠以及沙漠等一些极端气候区的花粉为一些先锋种植物提供必要的营养物质,具有重要的生态意义.     

陕西中部黄土高原地区空气花粉组成及其与气候因子的关系——以洛川县下黑木沟村为例

空气花粉研究是现代孢粉学、植被变迁与预测的重要内容之一.陕西省黄土高原地区洛川县2007-2009连续2a的空气花粉分析表明:空气花粉组成与区域植被分布特征和植物花期一致.与2007—2008年相比,2008-2009年的花粉总通量及蒿属花粉通量明显增加,但木本植物花粉通量降低,这主要与2008-2009年降水明显偏少密切相关.2007-2008年降雨量高于500 mm,花粉组合中乔木花粉百分比高于30％,表现出森林植被特点;2008-2009年降雨量少于450 mm,花粉组合中草本花粉高于80％,乔木花粉低于10％,更多表现出草原植被特点.但从植被观测来看并没有明显的变化,表明花粉组合较植被对气候变化更为敏感.主要花粉类型与气候因子的相关分析表明:气候因子影响空气花粉的组成及数量.栎属、松属、蔷薇科花粉数量主要受春季温度影响,温度越高花粉数量越多;其他季节花粉数量主要受相对湿度影响,湿度越低,花粉数量越大.榆属花粉数量主要与冬季温度有关,温度越高,花粉数量越高.杨属只受春季温度影响,春季温度越低,花粉数量越多.胡颓子科花粉含量主要受春季相对湿度、风速影响,相对湿度越低,风速越大,花粉数量越多.绝大多数草本花粉数量均主要受春、冬季相对湿度及风速影响,相对湿度越低,风速越大,花粉数量越高;此外,禾本科花粉数量还受春季温度影响,温度越高,花粉数量越多;菊科花粉数量在夏秋季节还受温度、湿度和风速的共同影响,温度越低,湿度越低,风速越大,花粉数量越多.这些结果表明,黄土高原中部地区的空气花粉特征能反映区域植被组成,且对气候变化非常敏感,对认识和预测当地气候变化与植被动态等具有重要意义.     

科尔沁沙地人工杨树林生态服务效能评价

采用定位观测法,系统评价了杨树(Populus simonii)林的防风、抗蚀和滞尘等生态服务效能及其间接价值,同时定量探讨了风速减弱系数与实测林地叶面积指数的关系。结果表明,在研究区主害风(西北风)天气下,林地迎风区6H(H为平均树高)、3H、林地中央、林地背风区林缘、6和8H处2m高度的日平均风速与对照点(流动沙丘)相比均有不同程度减弱,风速减弱系数在18．3％～66．2％之间。林地背风区6H处0．25、0．5、1和2 m 4个高度的月平均风速减弱系数与林地叶面积指数呈显著非线性相关,其间存在良好的三次曲线关系(P<0．0001,R²=0．43～0．94,n=80)。在主害风天气下,林地各观测点的地表日风蚀量与对照点相比大幅度降低,平均降幅85．2％～99．9％。在观测期内,林地中央的日平均降尘量为13.2 kg·hm^-2,而林地迎风区6H处的日平均降尘量为9．9 kg·hm^-2,林地的日滞尘能力约为3．3kg·hm^-2。       

Intrusion of airborne pollen through open windows and doors

The importance of the transport of pollen by air movement into houses was evaluated using six to eight simultaneously collecting rotorod-type samplers, creating either a sampler line from outdoors to inside the room, or a sampler grid inside a room. The number of incoming pollen grains was highly dependent on the outdoor concentration. The highest concentrations inside (1–2 m distance) and outside (1 m) the room were 600 and 3,250 grains/m³, respectively, in the Betula pollen season and 1,980 and 5,080 grains/m³ in the Pinus season. The pollen concentration and the indoor/outdoor (I/O) ratio decreased as the distance from the ventilation opening increased. Inside the room at a distance of 1–2 m 28%, and at a distance of 3–5 m 12%, of the outside concentration was recorded. In the lower part of the opening the mean proportion was 63% and in the upper part of the opening it was 40%. Efficient ventilation with two open windows increased the I/O ratio and enabled the pollen to spread throughout the room. During the Pinus pollen season 3–35% of the outdoor concentration was simultaneously recorded at six locations inside the room with two open windows and only 0.1–3.6% with one open window. At the same point in the room the I/O ratio varied from <1 to 35%, depending on the sampling conditions. Only a minor effect on the I/O ratio was found between small and large ventilation windows and the door, although it was expected that more air and pollen grains would come indoors through a larger opening.     

Annual variations of air-borne pollen in the Coastal Plain of Israel

A survey of airborne pollen was conducted during 1984 in the coastal plain of Israel. The flora of that area is continuously changing due to urbanization and agriculture, thus affecting the airborne pollen spectrum.

Significant pollen counts were monitored throughout the year, with a seasonal peak during spring. Meteorological parameters, such as wind velocity, wind direction and temperature affected pollen content of the air. Under certain conditions, even pollen of insect-pollinated plant species was found in the air.

The most conspicuous among the airborne pollen were olive, cypress and pine trees as well as pollen grains from the Poaceae, Amaranthaccae, Chenopodiaceae, Asteraceae, Brassicaceae and Urticaccae.

Results indicate that most of the airborne pollen grains were of local origin and from cultivated trees. Thus, it is possible to reduce airborne pollen contaminants around human habitations by selection of the proper non-allergenic ornamental plants.     

AERODYNAMICS OF WIND POLLINATION IN SIMMONDSIA CHINENSIS (LINK) SCHNEIDER

Wind tunnel analyses of Simmondsia chinensis (Link) Schneider or “jojoba” were conducted to quantify the behavior of airborne pollen grains around individual branches and leaves and near individual carpellate flowers. Field data (wind velocity) were used to ensure a correspondence between wind tunnel and natural conditions. Based upon the visualization of individual pollen grain trajectories, it is concluded that pollen deposition on stigmatic surfaces is influenced by large-scale aerodynamic patterns, generated by foliage leaves, and small-scale airflow patterns, formed around and by floral parts and stigmas. Leaves are seen to deflect airborne pollen grains into trajectories that can intersect ambient airflow at 90° angles, showering decumbent carpellate flowers with pollen. Similarly, flowers can deflect pollen upward and downwind, toward other flowers. The extent of floral bract and sepal recurvature is shown to influence the extent of pollen deposition by determining the characteristic airflow pattern around stigmas. Available evidence concerning the relatively recent evolutionary transition to anemophily in Simmondsia is interpreted within the context of morphological adaptations and exaptations favoring wind pollination.     

Wind‐mediated horseweed (Conyza canadensis) gene flow: pollen emission,dispersion, and deposition

Horseweed (Conyza canadensis) is a problem weed in crop production because of its evolved resistance to glyphosate and other herbicides. Although horseweed is mainly self-pollinating, glyphosate-resistant (GR) horseweed can pollinate glyphosate-susceptible (GS) horseweed. To the best of our knowledge, however, there are no available data on horseweed pollen production, dispersion, and deposition relative to gene flow and the evolution of resistance. To help fill this knowledge gap, a 43-day field study was performed in Champaign, Illinois, USA in 2013 to characterize horseweed atmospheric pollen emission, dispersion, and deposition. Pollen concentration and deposition, coupled with atmospheric data, were measured in a source field (180 m by 46 m) and its surrounding areas up to 1 km downwind horizontally and up to 100 m vertically. The source strength (emission rate) ranged from 0 to 140 pollen grains per plant per second (1170 to 2.1×10⁶ per plant per day). For the life of the study, the estimated number of pollen grains generated from this source field was 10.5×10¹⁰ (2.3×10⁶ per plant). The release of horseweed pollen was not strongly correlated to meteorological data and may be mainly determined by horseweed physiology. Horseweed pollen reached heights of 80 to100 m, making long-distance transport possible. Normalized (by source data) pollen deposition with distance followed a negative-power exponential curve. Normalized pollen deposition was 2.5% even at 480 m downwind from the source edge. Correlation analysis showed that close to or inside the source field at lower heights (≤3 m) vertical transport was related to vertical wind speed, while horizontal pollen transport was related to horizontal wind speed. High relative humidity prevented pollen transport at greater heights (3–100 m) and longer distances (0–1000 m) from the source. This study can contribute to the understanding of how herbicide-resistance weeds or invasive plants affect ecology through wind-mediated pollination and invasion.     

Patterns of pollen and seed dispersal in a small, fragmented population of the wind-pollinated tree Araucaria angustifolia in southern Brazil

Paternity analysis based on eight microsatellite loci was used to investigate pollen and seed dispersal patterns of the dioecious wind-pollinated tree, Araucaria angustifolia. The study sites were a 5.4 ha isolated forest fragment and a small tree group situated 1.7 km away, located in Paranalpha State, Brazil. In the forest fragment, 121 males, 99 females, 66 seedlings and 92 juveniles were mapped and genotyped, together with 210 seeds. In the tree group, nine male and two female adults were mapped and genotyped, together with 20 seeds. Paternity analysis within the forest fragment indicated that at least 4% of the seeds, 3% of the seedlings and 7% of the juveniles were fertilized by pollen from trees in the adjacent group, and 6% of the seeds were fertilized by pollen from trees outside these stands. The average pollination distance within the forest fragment was 83 m; when the tree group was included the pollination distance was 2006 m. The average number of effective pollen donors was estimated as 12.6. Mother-trees within the fragment could be assigned to all seedlings and juveniles, suggesting an absence of seed immigration. The distance of seedlings and juveniles from their assigned mother-trees ranged from 0.35 to 291 m (with an average of 83 m). Significant spatial genetic structure among adult trees, seedlings, and juveniles was detected up to 50 m, indicating seed dispersal over a short distance. The effective pollination neighborhood ranged from 0.4 to 3.3 ha. The results suggest that seed dispersal is restricted but that there is long-distance pollen dispersal between the forest fragment and the tree group; thus, the two stands of trees are not isolated.     

Precocious pollen germination in Arabidopsis plants with altered callose deposition during microsporogenesis

Pollination is essential for seed reproduction and for exchanges of genetic information between individual plants. In angiosperms, mature pollen grains released from dehisced anthers are transferred to the stigma where they become hydrated and begin to germinate. Pollen grains of wild-type Arabidopsis thaliana do not germinate inside the anther under normal growth conditions. We report two Arabidopsis lines that produced pollen grains able to in situ precociously germinate inside the anther. One of them was a callose synthase 9 (cs9) knockout mutant with a T-DNA insertion in the Callose Synthase 9 gene (CalS9). Male gametophytes carrying a cs9 mutant allele were defective and no homozygous progeny could be produced. Heterozygous mutant plants (cs9/+) produced approximately 50% defective pollen grains with an altered male germ unit (MGU) and aberrant callose deposition in bicellular pollen. Bicellular pollen grains germinated precociously inside the anther. Another line, a transgenic plant expressing callose synthase 5 (CalS5) under the CaMV 35S promoter, also contained abnormal callose deposition during microsporogenesis and displaced MGUs in pollen grains. We also observed that precocious pollen germination could be induced in wild-type plants by incubation with medium containing sucrose and calcium ion and by wounding in the anther. These results demonstrate that precocious pollen germination in Arabidopsis could be triggered by a genetic alteration and a physiological condition.     

Reproductive barriers in Annona cherimola (Mill.) outside of its native area

Cherimoya (Annona cherimola) is a subtropical tree crop of Andean origin whose fruit set results extremely low in farming areas outside of its natural occurrence. The lack of efficient pollinators and dichogamy are often argued to be the main constraints resulting in this low reproductive success. Herein, we describe the reproductive barriers exhibited by this crop and whether wind and insects play a role in cherimoya pollination in Spain, the main region of cultivation. A.?cherimola exhibits marked protogynous dichogamy with large differences in the duration of female (around 28?h) and male (<8?h) phases. Stigma receptivity and pollen release do not fully coincide with the morphological changes of the petals defining the female and male phases. Synchronization of sexual phases among different flowers from different trees of the same genotype was high during the whole blooming season. Effective herkogamy of approach type also limits pollen deposition within the same flower. Wind does not play any role in cherimoya pollination. Insect visitors to cherimoya flowers in Spain were found to be inefficient in transferring pollen grains. Cherimoya flowers do not reject self-pollen to achieve fertilization. A.?cherimola shows preferential allogamy based on efficient dichogamy reinforced by elevated synchrony among flowers in their sexual phases. Herkogamy hampers autogamy, although pollen deposition by gravity in cherimoya pendulous flowers explains the reduced reproductive success observed in isolated flowers.     

Long-distance pine pollen still germinates after meso-scale dispersal

Viability of long-distance pollen links ecological models to the genetic structure of forest tree populations, determining how forests will adapt to climate change and how far genes flow from genetically modified (GM) pine plantations. Addressing this landscape-scale inquiry is feasible when the pollen source, the delivery system, and the receiver field can be made explicit. To this end, I measured long-distance pollen germination along a 160-km transect along the North Carolina coastline, including 45000 ha of mature Pinus taeda plantations and barrier islands. Using this system, I tested three hypotheses: (1) pine pollen germinates after dispersal on meso-scale distances, (2) sodium chloride exposure reduces germination of pollen captured over open saltwater, and (3) viable pine pollen is present at high altitudes before local peak pollen shed. The experimental findings are as follows: pine pollen had germination rates of 2 to 57% after dispersal at distances from 3 to 41 km, sodium chloride solutions mildly reduced P. taeda pollen germination, and viable pine pollen grains were captured at an altitude of 610 m. GM pine plantings thus have a potential to disperse viable pollen at least 41 km from the source. Wind and rainfall, as integral parts of regional atmospheric systems, together exert a powerful influence on the genetic structure of forest tree populations.     

Pollen in aeolian dust with relation to allergy and asthma in Kuwait

The studying of spatial and temporal distribution of pollen is essential, but rarely tackled in the region including Kuwait. Pollen grains and aeolian dust in the state of Kuwait were seasonally monitored from August 2009 to August 2011 to identify and correlate spatially and temporally pollen data with human health asthma and allergy data. The year 2010–2011 yielded a high in deposited dust and pollen compared to 2009–2010 by 33.2 and 9.9%, respectively. The spring (April–May) and the autumn (October–November) seasons marked the most top pollen distribution for Chenopodiaceae, Gramineae (Poaceae), Cyperaceae, Fabaceae, and Plantaginaceae. The pollen graphs for summer (July–August) and winter (January–February) seasons showed low pollen distribution due to the severe drought, dust storms, winter wind and rainfall. There are no correlations found between pollen deposition and the number of asthma patients. The annual dust deposited rate in Kuwait during 2010/2011 was 373 t km^?2 which represented a 33.2% increase compared with 2009/2010. The study has concluded that pollen of Malvaceae, Compositae and Chenopodiaceae is the most common triggers of allergy in Kuwait. Additionally, a positive correlation between the number of allergy patients and deposited dust was observed during March 2010 and 2011.     

Mapping airborne pollen of papaya (Carica papaya L.) and its distribution related to land use using GIS and remote sensing

Papaya is an economically important plant in Thailand for domestic consumption and export. However, papaya is extremely susceptible to disease caused by the papaya ring spot virus. Although transgenic papaya has been developed, commercial cultivation of transgenic plants in Thailand is still illegal. One concern is cross-pollination to conventional varieties. In this study, windborne-pollen dispersion of papaya (Carica papaya L.) was investigated using geographic information systems (GIS) and remotely sensed data. Pollen traps were placed around a papaya plot in eight geographic directions, with radiuses varying from 5 to 900 m from the plot. Pollen counts were made for 12 different dates, and data were input into a GIS database. The distribution of pollen and its relation to land use were analyzed using land use data obtained from Quickbird imagery acquired during 2007. Comparative analyses of pollen dispersal, wind direction, and speed were made using data collected from a micro-climatic station set up at a papaya plot. The furthest distance from the plot that pollen was found was at 0.9 km, a distance at which only 1 pollen grain was found. The number of pollen grains carried by wind decreased as distance increased. The direction of dispersal was not in accordance with wind direction data. Most pollen grains were found in agricultural areas and bare land. The total number of pollen grains found in exposed areas was considerably higher than the total found in areas sheltered by dense tree lines.     

Airborne conifer pollen grains are rarely deposited on stigmas of coflowering insect‐pollinated angiosperms

Although plant species with either animal or wind pollination modes are widespread and usually sympatric in nature, the degree of pollen interference from wind‐pollinated species on animal‐pollinated species remains little known. Conifer trees generally release a huge number of pollen grains into the air, floating into our noses and sometimes causing an allergic response. Here we document airborne pollen from two conifers (Pinus densata Mast. and Picea likiangensis (Franch.) E. Pritz.) deposited on the stigmas of eight coflowering insect‐pollinated angiosperms over 2 years in a mountainous forest community, in Shangri‐La, southwest China. Pollen density in the air as well as conifer pollen deposited onto stigmas at short and long distances from the airborne pollen source were quantified. Our results showed that conifer pollen as a proportion of total stigmatic pollen loads in the insect‐pollinated plants varied from 0.16% to 8.67% (3.16% ± 0.41%, n = 735) in 2016 and 0.66% to 5.38% (2.87% ± 0.86%, n = 180), and pollen quantity per unit area was closely related to that of airborne pollen in the air. Conifer pollen deposition on stigmas of insect‐pollinated species decreased greatly with increased distance from the pollen source. In the 10 plant species flowering in summer after conifer pollen release had finished, heterospecific pollen deposited on these stigmas came mainly from other insect‐pollinated flowers, with little contribution from airborne conifer pollen. The results indicate that there might be little interference with coflowering angiosperms by airborne pollen from dominant conifers in natural communities.     

WIND POLLINATION OF TAXUS CUSPIDATA

The air disturbance patterns created by and around the ovules of Taxus cuspidata are quantified for various orientations to the direction of ambient airflow, and are shown to largely dictate the motion (vectoral trajectories) and mode of deposition of windborne pollen on ovule surfaces. Perpendicular orientation to the direction of airflow results in two regions characterized by high densities of adhering pollen — one on the windward surface of the ovule, resulting from direct inertial collision, and another on the leeward surface resulting from non-inertial sedimentation. Parallel and inclined orientations of the ovule to the direction of airflow produce quantitative and qualitative variations in the pattern of adhering pollen resulting from inertial and non-inertial deposition. Direct collision of windborne pollen grains with the micropylar ends of ovules occurs for all orientations to wind direction. The aerodynamics of the ovulate shoot complex of Taxus cuspidata is related to that previously described for conifer ovulate cones, cycad megastrobili, and simulated wind tunnel analyses of archaic Paleozoic ovules based on scale models. Water transport of pollen (adhering to integument and bract surfaces) to micropyles quantitatively alters the distribution of adhering pollen grains on ovule surfaces. Although there is no evidence that pollen grains of this species are osmotically ruptured, observations do not preclude the possibility that water transport of pollen may reduce the number of viable pollen grains reaching the micropyle.     

Towards numerical forecasting of long-range air transport of birch pollen: theoretical considerations and a feasibility study

This paper considers the feasibility of numerical simulation of large-scale atmospheric transport of allergenic pollen. It is shown that at least small grains, such as birch pollen, can stay in the air for a few days, which leads to a characteristic scale for their transport of ∼10³ km. The analytical consideration confirmed the applicability of existing dispersion models to the pollen transport task and provided some reference parameterizations of the key processes, including dry and wet deposition. The results were applied to the Finnish Emergency Dispersion Modelling System (SILAM), which was then used to analyze pollen transport to Finland during spring time in 2002–2004. Solutions of the inverse problems (source apportionment) showed that the main source areas, from which the birch flowering can affect Finnish territory, are the Baltic States, Russia, Germany, Poland, and Sweden—depending on the particular meteorological situation. Actual forecasting of pollen dispersion required a birch forest map of Europe and a unified European model for birch flowering, both of which were nonexistent before this study. A map was compiled from the national forest inventories of Western Europe and satellite images of broadleaf forests. The flowering model was based on the mean climatological dates for the onset of birch forests rather than conditions of any specific year. Utilization of probability forecasting somewhat alleviated the problem, but the development of a European-wide flowering model remains the main obstacle for real-time forecasting of large-scale pollen distribution.     

Terminal settling velocity and physical properties of pollen grains in still air

Numerical simulation of wind pollination requires knowledge of pollen grain physical parameters such as size, shape factor, bulk density, and terminal settling velocity. The pollen grain parameters for Japanese cedar, Japanese cypress, short ragweed, Japanese black pine, and Japanese red pine were assessed for dry condition. Terminal settling velocities of dry pollen grains in still air were measured using image analysis of scattered light tracks in a dark settling tube. The measurement system was validated by comparing results to those obtained for standard microspheres of known size and density. Dry pollen grain shape factors indicate the resemblance of particles to spheres, except for pine pollen. Circularity factors of dry pine pollen grains were 0.90–0.86, suggesting more irregular shape than those of other pollen species. Aerodynamic diameters of dry pollen grains were calculated based on the terminal settling velocity. Aerodynamic diameters of Japanese cedar, Japanese cypress, and short ragweed closely resembled the projected area equivalent diameters, suggesting that aerodynamic behaviors of these pollen grains can be managed simply in numerical simulations. However, aerodynamic diameters of dry pine pollen grains were nearly 30 % smaller than projected area equivalent diameters. Sacci on dry pine pollen can reduce the terminal settling velocity through low density and shape effects attributed to their non-sphericity, engendering aerodynamic diameter smaller by more than 10 µm from area equivalent diameters.