If you would like to submit feedback regarding any Health Tags direct all correspondence to:

Ann Allergy Asthma Immunol, Vol. 96, No. 1. (January 2006), pp. 86-91.BACKGROUND: Ambrosia pollen is an important allergen in North America and, as recently discovered, in some European countries. In Italy, the most affected area is the northeast, whereas ragweed has not been reported in the central and southern parts of the country. OBJECTIVE: To identify the source of ragweed pollen detected in Florence and Pistoia in central Italy. METHODS: Ragweed pollen data were collected in Florence and Pistoia for a 6-year period (1999-2004). The relationship between pollen counts and local ground prevalent wind directions was evaluated with analysis of variance and the least significant difference test. Weather conditions were also evaluated on a large-scale circulation pattern by analyzing weather maps and air mass back trajectories. RESULTS: A highly statistically significant relationship between daily prevailing wind direction and pollen count was found in the period under investigation; the ragweed pollen peaks were recorded when winds from northeast in Florence and north-northeast in Pistoia were observed. The synoptic weather situation and the path of back trajectories suggest an area around southern Hungary as a possible source of Ambrosia pollen. Furthermore, the pollen count was above the clinical threshold several times in both Florence and Pistoia. CONCLUSIONS: Several factors indicate that the detection of ragweed pollen in central Italy is due to long distance transport. Taking into consideration the high allergenicity of Ambrosia pollen, the present findings, if confirmed, suggest that the number of sensitized individuals might significantly increase in the near future.L Cecchi, C Lorenzo, M Morabito, M Marco, M Paola Domeneghetti, DM Paola, A Crisci, C Alfonso, M Onorari, O Marzia, S Orlandini, O Simone, citeulike.org

Science, Vol. 286, No. 5445. (26 November 1999), pp. 1697-1700.10.1126/science.286.5445.1697Christel Schopfer, Mikhail Nasrallah, June Nasrallah, citeulike.org

Flora - Morphology, Distribution, Functional Ecology of Plants, Vol. 200, No. 5. (6 September 2005), pp. 399-415.Two types of sticky pollen coat material exist in angiosperms, both produced by the anther tapetum. Pollenkitt is the most common adhesive material present around pollen grains of almost all angiosperms pollinated by animals, whereas tryphine seems to be restricted only to Brassicaceae. Tapetal cell protoplasts have different patterns of development according to the products formed during their development and degeneration. If tryphine is formed, the tapetal cell protoplasts lose their individuality at the microspore stage. If pollenkitt is formed, their contents degenerate at later stages. Cell content is totally reabsorbed, when ripe pollen is not surrounded by any gluing material. Current knowledge of pollenkitt formation, deposition on pollen grains and chemical composition are reviewed and discussed. Methods for detecting this viscous fluid are also presented. The many functions of pollenkitt, deduced from personal observations and the literature, act in the period between anther opening and pollen hydration on the stigma; they are: (1) to hold pollen in the anther until dispersal; (2) to enable secondary pollen presentation; (3) to facilitate pollen dispersal; (4) to protect pollen from water loss; (5) to protect pollen from ultra-violet radiation; (6) to maintain sporophytic proteins responsible for pollen-stigma recognition inside exine cavities; (7) to protect pollen protoplasts from fungi and bacteria; (8) to keep together pollen grains during transport; (9) to protect pollen from hydrolysis and exocellular enzymes; (10) to render pollen attractive to animals; (11) to render pollen visible to animal eyes; (12) to hide pollen from animal eyes; (13) to avoid predation of pollen through smell; (14) to enable adhesion to insect bodies; (15) to enable pollen packaging by bees and to form corbicules; (16) to provide a digestible reward for pollinators; (17) to enable pollen clumps to reach the stigma; (18) to allow self-pollination; (19) to facilitate adhesion to the stigma; (20) to facilitate pollen rehydration. Depending on the developmental program of the species, these functions may act during pollen presentation, in relation to pollinators, during pollen dispersal and when pollen reaches the stigma.Ettore Pacini, Michael Hesse, citeulike.org

Plant Systematics and Evolution, Vol. 222, No. 1. (1 March 2000), pp. 133-142.This paper reviews research on the role of electrostatic forces in pollination, both in natural and in agricultural systems. Researchers from various fields of biological studies have reported phenomena which they related to electrostatic forces. The theory of electrostatically mediated pollen transfer between insect pollinators and the flowers they visit is described, including recent studies which confirmed that the accumulated charges on airborne honey bees are sufficient for non-contact pollen detachment by electrostatic forces (i.e., electrostatic pollination). The most important morphological features in flower adaptiveness to electrostatic pollination were determined by means of two theoretical models of a flower exposed to an approaching charged cloud of pollen; they are style length and flower opening. Supplementary pollination by using electrostatic techniques is reported, and its possible importance in modern agriculture is discussed.Y Vaknin, S Gan-Mor, A Bechar, B Ronen, D Eisikowitch, citeulike.org

Plant, Cell and Environment, Vol. 5, No. 2. (1982), pp. 125-129.The measurements of Yes'kov & Sapozhnikov (1976) suggest that electrostatic potentials on foraging honeybees can reach hundreds of volts. Pollen grains of oilseed rape, Brassica napus L., subjected experimentally to potentials of this order, jumped a distance that increased approximately as the square of the voltage, between two pin electrodes on which, in some experiments, were impaled an anther or stigma of oilseed rape or a freshly-killed honeybee. Most floral surfaces were insulated, but there was a low-impedance path to earth via the stigma, and the electrostatic field due to an approaching charged bee must therefore concentrate there. Thus, if electrostatic potentials of this magnitude occur in nature they may increase the chance that pollen from bees will reach the stigma rather than other floral surfaces, as well as enabling pollen to jump from anther to bee and from bee to stigma across an air gap of the order of 0.5 mm.Sarah Corbet, James Beament, D Eisikowitch, citeulike.org

TAG Theoretical and Applied Genetics, Vol. 65, No. 3. (1 May 1983), pp. 231-238.A simple medium is described which supports the germination of Brassica pollen in vitro. The method is completely reliable and the percentage germination achieved is comparable to that found on a compatible stigma. The pollen tubes produced attain lengths equal to those growing in the style and exhibit similar growth kinetics. The major difference between this medium and other less-reliable media is the addition of 1 mM Tris. The efficacy of Tris is shown to be due in part to the establishment of an optimum pH but an ?amine effect? is also identified. The optimum pH for growth in vitro may be different from that encountered on the stigma. Atmospheric concentration of CO2 and pollen population density are also shown to have pronounced effects on germination in vitro.IN Roberts, TC Gaude, G Harrod, HG Dickinson, citeulike.org

Review of Scientific Instruments, Vol. 69, No. 2. (1998), pp. 466-468.S Sakalauskas, A Sodeika, citeulike.org

J Cell Sci, Vol. 80, No. 1. (1 February 1986), pp. 141-157.CJ Elleman, HG Dickinson, citeulike.org

New Phytologist, Vol. 110, No. 4. (1988), pp. 557-569.Morphological, genetic, and biochemical data on the sporophytic self-incompatibility (SI) system of Brassica spp. are evaluated and compared with those from host-pathogen (HP) interactions which conform to the gene-for-gene hypothesis and are characterized by the production of phytoalexins. SI and HP systems have many features in common, reflecting similarities in the processes of discrimination, particularly with respect to the response to an incompatible recognition event. Thus, both recognition reactions involve cell surface components which are likely to be glycoproteins in at least one of the partners. Both incompatible responses are active processes requiring enzyme synthesis, are biostatic rather than biocidal with respect to pollen and pathogen, and are accompanied by the production of low molecular weight phytoalexin-like compounds. Recent evidence also suggests that incompatible HP interactions may involve recognition of 'self' cell wall components. These similarities are distinguished from those, such as the production of cuticle and cell wall degrading enzymes, which may result only from the common requirement of pollen and pathogen to penetrate through the plant surface. The significance of the most obvious differences between the two systems, such as the evidence that SI may be mediated through the supply of water lo the pollen grain and the absence, in SI interactions, of cell necrosis or 'cross protection' reactions is also explored. It is suggested that some of the observed differences may result from 'pre-programming' of the SI response.T Hodgkin, GD Lyon, HG Dickinson, citeulike.org

Journal of cell science, Vol. 42 (April 1980), pp. 417-423.The adhesion of pollen grains to the stigmas of Brassica oleracea was assayed after treatment of the stigmas wiuth protease and/or cycloheximide. Treatment with protease alone adversely affected pollen grain adhesion. However, the adhesive properties of the stigma recovered fully if the stigmas were not pollinated until 2 h after treatment. Immersion of the stigmas in cycloheximide after protease treatment prevented any recoveryt of the stigmas' adhesive properties. Cycloheximide treatment alone prevented pollen grain adhesion when pollination occurred later than 1--2 h after treatment but did not affect pollen grain adhesion if pollination occurred immediately after treatment. These results indicated not only that the surface-held proteins of the stigma are involved in pollen grain adhesion, but also that their turnover rate is rapid. Isoelectric focusing of extracts derived from stigmas after protease and cycloheximide treatment showed a marked decrease in staining intensity of 3 protein bands, one of which, a glycoprotein, is known to be present only when the self-incompativility system is fully functional. These observations suggest a specificity of adhesion between higher plant cells in the presence of the cell wall.AD Stead, IN Roberts, HG Dickinson, citeulike.org