Pollen monitoring in Perugia and information about aerobiological data

Summary The results of six years (1982–1987) of aerobiological study in Perugia (central Italy) are reported. During this period a total of 80 different types of pollen belonging to 52 families were identified in the Perugia atmosphere. The highest percentages of pollens were found in the mid-March to mid-July period. For main taxa principal periods of pollination were identified. The outlines for the weekly issue in a newspaper of the concentration pattern of the allergenic pollens are reported.     

Types of pollen dispersal units in orchids,and their consequences for germination and fertilization

The various pollen dispersal units (PDU) found in orchids are discussed together with possible evolutionary trends and the consequences for germination and fertilization. Orchids with monad and tetrad pollen form more complex dispersal units by means of pollenkitt, elastoviscin, a callosic wall, common walls or a combination of these. Evolutionary trends include (1) from pollenkitt to elastoviscin; (2) from monad to tetrads and multiples of tetrads; (3) from partially dehydrated (<30 %) to partially hydrated (>30 %) pollen; and (4) from monad pollen to PDUs with many pollen grains. The biological consequences concern both male and female reproductive systems. Some features of the male side are present in all orchids irrespective of the pollen dispersal unit, whereas other characters are found only in orchids with pollinia; the same applies for the female counterpart. Pollen grains of orchids with pollinia germinate at least 24 h after pollination because the pollen grains/tetrads must swell and make space for the growth of pollen tubes.     

Pollen layering and male–male competition: Quantum dots demonstrate that pollen grains compete for space on pollinators

Premise

Almost nothing is known about what happens to pollen grains once they attach to pollinators, although some have postulated that pollen from different donors may form complex, two- or three-dimensional landscapes (e.g., layers or mosaics) that can facilitate male–male competition. For example, pollen that is already on pollinators may preclude the deposition of subsequent pollen grains.

Methods

Using quantum dots to mark the pollen of individual flowers, we explored the possibilities of layering and preclusion in a fly-pollinated iris, Moraea lurida.

Results and Conclusions

The proportion of labeled pollen from the last flower visited diminished in sequential pollen samples taken from the top to the bottom of the pollen load, representing the first empirical evidence for pollen layering. However, the consequences in terms of pollen preclusion were equivocal: Although the pre-existing pollen load size was not a good predictor of new pollen receipt, labeled pollen loads from the last flower visited were significantly smaller than pollen loads from the previous flower visited. Thus, pollen from the previous flower may preclude pollen placement from a subsequently visited flower, and pollen from different flowers may compete for space on pollinators.

     

Consumptive emasculation: the ecological and evolutionary consequences of pollen theft

Many of the diverse animals that consume floral rewards act as efficient pollinators; however, others 'steal' rewards without 'paying' for them by pollinating. In contrast to the extensive studies of the ecological and evolutionary consequences of nectar theft, pollen theft and its implications remain largely neglected, even though it affects plant reproduction more directly. Here we review existing studies of pollen theft and find that: (1) most pollen thieves pollinate other plant species, suggesting that theft generally arises from a mismatch between the flower and thief that precludes pollen deposition, (2) bees are the most commonly documented pollen thieves, and (3) the floral traits that typically facilitate pollen theft involve either spatial or temporal separation of sex function within flowers (herkogamy and dichogamy, respectively). Given that herkogamy and dichogamy occur commonly and that bees are globally the most important floral visitors, pollen theft is likely a greatly under-appreciated component of floral ecology and influence on floral evolution. We identify the mechanisms by which pollen theft can affect plant fitness, and review the evidence for theft-induced ecological effects, including pollen limitation. We then explore the consequences of pollen theft for the evolution of floral traits and sexual systems, and conclude by identifying key directions for future research.     

燕山南部花粉散布特征

燕山南部花９粉用布特性研究表明,空气中的花粉反映的是植物花期的季节性变化,表 粉是植物多年花粉散布的混合,冲积物花粉与空气中和表土花粉显著不同,是取样点上游表土花粉的混合,与取样点周围植被关系较小。因此,根据冲积物花粉恢复古植被,反映的是整个流域的植被面貌,而不是某一点的植被特征。     

The collection of pollen by bees

Bees require pollen for their reproduction and pollen comprises the basic larval food for bees. Most bees acquire pollen passively during flower visitation, but female bees may also collect pollen actively with the aid of various structural and behavioral adaptations. Most bees have evolved adaptations to concentrate pollen into discrete loads and transport pollen back to their nests. The various structural and behavioral adaptations of female bees for acquiring and transporting pollen are the basis of this review.     

Pollen germination and pollen tube growth in Fraxinus pennsylvanica

With regard to adaptation of green ash (Fraxinus pennsylvanica Marshall) to ecological conditions in Croatia, pollen germination and pollen tube length after 2, 4 and 6 hours were examined in vitro at 10, 15, 20 and 25°C during two years 2001 and 2002. Narrow leaved ash (F. angustifolia Vahl) pollen served as a control in 2002. The year, time and temperature, and the interaction between time and temperature were significant for both germination percentage and pollen tube length. Interactions year × temperature and year × time were significant for pollen tube length only. The highest germination percentage (17.86% in 2001 and 19.40% in 2002) of green ash pollen was at 15°C after 6 hours. The pollen tube length was greatest at 20°C (393.46 μm) in 2001 and 25°C (899.50 μm) in 2002 after 6 hours. Narrow leaved ash pollen had the highest germination percentage (19.22%) at 20°C after 6 hours and was significantly reduced at 25°C. The pollen tube length was greatest at 25°C (518.90 μm) after 6 hours. It can be concluded that green ash pollen has satisfactory germination in ecological conditions in Croatia and that the optimum temperature for pollen germination is higher than 20°C.     

Pollen viability,germination capability and pollen production level of some grape varieties (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.)

In this study, pollens of Burdur dimriti, Sariemin, Tilki kuyrugu, Razaki, Buzgulu, Siyah buzgulu, and Siyah gemre table grape varieties (Vitis vinifera L.) grown in Isparta, Turkey were tested in vitro for viability, germination capability, and production level. It was determined that active pollen levels varied between 23.8 % and 80.8 % in FDA (flourescein diacetat), 31.5 % and 68.8 % in TTC (2,3,5-triphenyl tetrazolium chloride) tests. In respect to pollen germination rates, the best medium in hanging drop method and saturated petri method were 20 % sucrose concentration and 1 % agar+15 % sucrose solution, respectively. The highest and the lowest pollen production levels per flower were determined 9000 in Siyah gemre and 2906 in Siyah dimrit grape varieties, respectively.     

Structure and development of the stigma, style and ovary of Caesalpinia pulcherrima (L.) Sw., post-anthesis, pre- and post-pollination

The stigma of Caesalpinia pulcherrima is crateriform. The crater continues as a slit-like canal through the style and into the ovary. Both crater and canal are lined by several layers of fusiform and thin-walled cells which are continuous in two narrow regions in the ovary. Postanthesis and before pollination, the middle lamella of cells lining the stigmatic crater and stylar transmitting tissue undergoes dissolution. This occurs in a progression down the style with cells separating partially or wholly from neighbours. Dissolution is initiated at intercellular junctions where wall fibrils loosen and variously-sized and -shaped holes appear. Cytoplasmic changes include increased dictyosome activity, increased rough and smooth endoplasmic reticulum at the periphery of cells and accumulation of electron opaque deposits at the plasma membrane. The crater fills with stigmatic fluid and the diameter of the stylar canal increases. Pollen germinates in the secretion-filled crater, and pollen tubes grow down the style between the cells of the transmitting tissue but do not enter the canal. They emerge at the entrance to the ovary cavity and grow over one or two narrow strips of ovarian transmitting tissue cells which are present throughout the length of the ovary close to the ovules. This ensures that tubes grow in close proximity to the micropyles.     

Exposure of Betula pendula Roth pollen to atmospheric pollutants CO,O3 and SO2

Betula pendula pollen, under laboratory conditions, was exposed to three atmospheric pollutants: carbon monoxide (CO), ozone (O₃) and sulphur dioxide (SO₂). Two levels of each pollutant were used; the first level corresponds to a concentration on the atmospheric hour-limit value acceptable for human health protection in Europe, the second level to a higher, at least more than double of the first, concentration level. Experiments were done under artificial solar light with controlled temperature and relative humidity. Our results indicate that, in urban areas, concentrations of CO, O₃ and SO₂ on the limits established for human protection, can affect pollen fertility. We verified a decrease in the viability and germination of the pollen, indicating damage to the pollen membrane system. Also, a general decreasing trend in the total protein content of the exposed samples when compared with the control samples was observed, which suggests alterations in the antigenic characteristics of pollen.     

Birch pollen production,transport and deposition for the period 1984–1993 at Kevo,northernmost Finland

Summary Betula pollen production and flowering, pollen transport and pollen deposition are considered for the mountain birch region of northern Finland for the ten-year period 1984–1993. The most abundant flowering year was 1989 and, after that, 1985. In these years the highest values were also recorded for pollen in the air. There is a significant correlation between the amount of pollen released and the thermal sum of the previous year. In terms of pollen deposition the peak years were 1989 and 1986. The correlation between the amount of pollen in the air and that being deposited on the ground is also statisticaly significant. It is evident that some birch pollen is already present in the air before local flowering begins and that, in some years, this non-local pollen can account for more than 20% of the yearly total. This preflowering proportion was highest in 1985 and 1993, the latter being a prolific flowering year in the south of the country. There is a clear relationship between the proportion of the non-local pollen in the air and the proportion ofBetula pubescens/pendula type pollen deposited on the ground and, conversely, there is a significant correlation between the amount of local pollen in the air and the amount ofBetula tortuosa plusB. nana type pollen being deposited on the ground. The questions both of the viability of this long-distance pollen and of its ability to cause allergic reactions are considered. An assessment is also made of the degree to which fossil birch pollen assemblages can be realistically interpreted in terms of local vegetation if a varying proportion of the same pollen type is non-local.     

City spore concentrations in the European Economic Community (EEC). VI. Poaceae (Grasses), 1982–1986

Summary Airborne grass-pollen concentrations in six cities in the EEC are compared, based on observations from five years, 1982–1986. Results show that there are quantitative differences both between the monitoring stations and between the years. Very provisionally, the average seasonal total of the European urban airborne grass-pollen concentration can be put at 4 to 5000 per m³ of air. Also qualitatively, regarding the seasonal fluctuations, there are differences between the stations, and between the years. Generally, the results confirm that June is the most typical grass-pollen month in northwestern Europe, whereas in mediterranean Europe May is the more prominent grass-pollen period. There seems to be little coherence between the starting dates of the grass-pollen season even at relatively nearby stations in northwestern Europe, suggestive for a great influence of the actual weather situation.     

Pollen competition between morphs in a pollen‐color dimorphic herb and the loss of phenotypic polymorphism within populations

Flower color polymorphism is relatively uncommon in natural flowering plants, suggesting that maintenance of different color morphs within populations is difficult. To address the selective mechanisms shaping pollen‐color dimorphism, pollinator preferences and reproductive performance were studied over three years in Epimedium pubescens in which some populations had plants with either green or yellow pollen (and anthers). Visitation rate and pollen removal and receipt by the bee pollinator (Andrena emeishanica) did not differ between the two color morphs. Compared to the green morph, siring success of the yellow morph's pollen was lower, but that of mixtures of pollen from green and yellow morphs was lowest. This difference, corresponding to in vivo and ex vivo experiments on pollen performance, indicated that pollen germination, rather than tube growth, of the green morph was higher than that of the yellow morph and was seriously constrained in both morphs if a pollen competitor was present. A rare green morph may invade a yellow‐morph population, but the coexistence of pollen color variants is complicated by the reduced siring success of mixed pollinations. Potential pollen competition between morphs may have discouraged the maintenance of multiple phenotypes within populations, a cryptic mechanism of competitive exclusion.     

Isolation and Artificial Germination of De-exined Pollen in Brassica

In view of the fact that pollen deprived of exine has been shown by electroporation to be a superior receptor of foreign genes in tobacco, the authors developed a technique to isolate and artificially germinate the de-exined pollen in Brassica. Pollen grains of B. chinens/s and B. campestris var. purpurea were first hydrated at 4 ℃ in a medium containing Roberts' salts, 24% sucrose, 7.3% mannitol, 0.05% lactoalbumin hydrolysate (pH 8.5) for 18 h, followed by heat shock at 34 ℃ for 40～60 min and osmotic shock for 20 min subsequently. Through this three-step procedure the exine could dehisce along the germination furrows and completely detached off, resulting in the release of pollen coated with naked intine with an isolation rate as high, as over 60%. The de-exined pollen were germinated in a modified medium containing 15%～20% polyethylene glycol (MW 6000), 5% sucrose, 0.05% lactoalbumin hydrolysate and Roberts' salts (pH 8.5) with a rate of 41% in B. chinensis and 33% in the other species. However, in sharp contrast with the behavior of the intact pollen, the de-exined pollen did not germinate in the carbon and nitrogen sources free media. Scanning electron microscopic and light microscopic observations on the processes of isolation and germination of de-exined pollen were carried out. The phenomenon of exine detachment in a few plant species is reviewed. There might be some corresponding association between pollen wall characteristics and methods of isolation. The de-exined pollen may be a useful experimental system not only for introducing and transferring foreign genes, but also for investigating the role of exine in pollen germination and in sporophytic self-incom- patibility.     

Monitoring pollinosis and airborne pollen in a Rome university

Pollen allergies and airborne pollen weremonitored at the University of Rome ``TorVergata' in 1999 in order to determine theconcentration and the quality of airbornepollen belonging to allergenic plants inrelationship to the prevalence of pollenallergies.Airborne pollen was monitored by volumetrictrap while data on allergies were collectedthrough a questionnaire distributed to theUniversity personnel belonging to variousworking categories. Meteorological data wereobtained through a daily monitoring carried outby a meteorological station while plantanthesis identification was done at theHerbarium of the University.Results indicated that prevalent allergies weredue to Gramineae, Urticaceae and Oleaceaepollen. Many subjects suffering from allergiesdid not know the responsible allergen(s) andmore than half of the allergic subjects statedto have allergic relatives.Data on pollen monitoring and prevalence ofallergies, collected in the same geographicalarea, were found to be in accordance with eachother, with the exception of the case ofCupressaceae/Taxaceae plants, whose pollen wasfound in high concentration although no case ofallergy due to this pollen was established.     

Pollen survey and clinical research in Yunnan, China

This pollen survey includes 7 counties of Yunnan Province, China: Quinjin, Xishuanbanna, Lijiang, Wenshan, Yuxi and Kunming. From 1991–1992, optical and statistical examination of exposed glass slides showed that pollen is air-borne in Yunnan throughout the year. Pollen is also in great quantity and variety with two apparent pollen peaks. This paper also discusses the influences of climate and elevation on the amount of pollen carried by air. A geographical and seasonal variation of pollen level was established. The pollen particles causing possible sensitization were collected in the field and refined into an allergen extract which was applied to clinical tests for patients suffering from allergosis in our hospital with a high rate of pollen allergy. The results show the effectiveness of specific desensitization for pollen allergic patients. This study is therefore of great significance to the diagnosis,treatment and prevention of pollen allergy.     

Morphology of pollen and orbicules in some Dioscorea species and its systematic implications

Pollen and orbicule morphology of 35 Dioscorea L. species is described based on observations with light microscopy, and scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the genus. Pollen is mostly bisulcate (sometimes monosulcate) with a perforate, microreticulate or striate sexine. Our results indicate that pollen data may be significant at sectional rank. The close relationship between sections Asterotricha and Enantiophyllum proposed by Burkill and Ayensu is supported by pollen morphology as all species investigated share bisulcate, perforate pollen with small perforations and a high perforation density. Macromorphological differences between the two compound-leaved sections Botryosicyos and Lasiophyton are also supported by pollen morphology; pollens of these two sections have very different perforation patterns. Orbicules in Dioscorea are mostly spherical and possess a smooth or spinulose surface. The latter is often correlated with a striate sexine.