AN ANALYSIS OF THE CONTENT OF PTERIDOPHYTA SPORES IN AEROPLANKTON OF LUBLIN (2013–2014)

Similarly to fungal spores and pollen grains, pteridophytic spores can cause allergies in humans. Pteridophyta spore concentrations in the air of Lublin, under the conditions of central-eastern Poland, were first studied over the period 2013–2014. The volumetric method was used in this study. The research showed that that spores of ferns belonging to the following genera: Asplenium, Athyrium, Blechnum, Botrychium, Cystopteris, Dryopteris, Matteuccia, Osmunda, Polypodium and Pteridium, occur in aeroplankton. Spores were recorded in low concentrations and they occurred in a dispersed pattern during the season. They were found to be absent on some days. Among the above-mentioned genera, Dryopteris and Athyrium showed the highest content of spores in aerosol. In both years of the study (2013 and 2014), similar annual spore counts were recorded, respectively 69 and 63. The most spores were identified in August.

The above-mentioned aeroplankton components are carriers of allergenic proteins which can cause allergies in humans and animals and therefore are treated as environmental pollutants [1,3,4]. A study conducted by allergists in Singapore showed high sensitivity of many patients to spores of six fern species, among others Asplenium nidus, Nephrolepsis auriculata, and Pteridium aquilinum. Allergic reaction was observed in 20 -34% of patients in whom skin tests were performed using extracts from particular fern species [5]. Spores of Pteridium aquilinum and several other ferns were also found to have cancerogenic properties [6].
Aerobiological research on Pteridophyta spores is carried out on a small scale in the world. Among 215 genera representing Pteridophyta, distributed mainly in the tropics and subtropics, aerobiological monitoring has identified 49, including 42 in the studies conducted in Asia [7]. In the literature, only several papers can be found which relate to the airborne spore content of Pteridophyta in Europe: in Rothamsted [8] and Edinburgh [9] (UK), in Rzeszów (Poland) [10], and in Salamanca (Spain) [11].
The morphological characteristics of pteridophytic spores of 44 species belonging to 18 genera and 13 families occurring in Poland are presented by Z e nk t e l e r [12].
The aim of this study was to conduct, for the first time, monitoring of fern spore concentrations in the air of Lublin, which is located in central-eastern Poland. The investigations were carried out over a period of 3 months (June -August) during two successive years (2013-2014). The research undertaken will allow us to evaluate the degree of air pollution in Lublin by Pteridophyta spores which are an aeroplankton component; these spores can be environmental biopollutants posing a threat to human health.

MATERIALS AND METHODS
The study material consisted of airborne Pteridophyta spores trapped in Lublin -a city located in the central east part of Poland, on the northern edge of the Lublin Upland. Spore monitoring was carried out from  In this trap, matter particles are aspirated together with air through a narrow orifice (2 × 14 mm) at a rate of 10 l per minute, which is similar to the volume of air inhaled in humans. The sampler has a circular drum driven by a clock mechanism rotating at a speed of 2 mm per hour. The Melinex tape is mounted on a cylinder and coated with silicone oil. Every week at the same time the tape is replaced with a new one. Subsequently, the tape is cut into 48 mm sections corresponding to 24-h periods and microscope slides are prepared using glycerol-gelatine with the addition of basic fuchsin dye. The next step is to analyze the material under a light microscope at a 400-fold magnification. Spores are counted along four horizontal lines. The number of spores obtained is multiplied by a correction factor, which depends on the magnification applied, width of the field of view, and the surface area of the slide. The concentration of spores is expressed as the number of spores in 1 m 3 of air.
Identification of pteridophytic spores was done based on the data contained in the publications by T r yo n and L u g a r d o n [13] and by Z e n k t e l e r [12].

RESULTS
In 2013 spores of Pteridophyta belonging to 9 taxa (eight ferns and Equisetum) were identified in the aerobiological slides analyzed ( Table 1). Images of the studied fern genera viewed under a light microscope are shown in Figure 1 (a-o). Spores of Asplenium, Athyrium, Blechnum, Botrychium, Cystopteris, Dryopteris, Matteuccia and Polypodium were identified during the monitoring.
In 2014 spores of 8 fern genera were also distinguished, but among them there were two other genera (Osmunda, Pteridium) than in the previous year ( Table 2). On the other hand, spores of Blechnum and Cystopteris were not found.
Each year over the 3-month study period during the growing season, the highest number of fern spores per 1 m 3 of air was recorded in August. July was the next month that was also abundant in airborne spores of some Pteridophyta taxa ( Table 1, 2). In both years, similar Pteridophyta spore counts were recorded (69 and 63 spores m -3 ).
In 2013 the maximum concentrations recorded during the season of airborne Pteridophyta spores were 3 spores m -3 , while in 2014 they were 5 spores m -3 (Fig.  2, 3).
The most spores identified in the slides belonged to the genera Dryopteris (on average 32) and Athyrium (on average 18). In both years, the maximum Dryopteris spore concentrations were recorded in the third 10-day period of June ( Fig. 4). Spores of this taxon were not found in the air on some days during the investigated seasons. On the other hand, the Athyrium spore season began at the end of the second 10-day period of July (2014) or in the third 10-day period of this month (2013) (Fig. 5). The highest concentrations of spores of this genus were observed in different 10-day periods of August in both years.

DISCUSSION
Most studies involving monitoring of pteridophytic spores in aeroplankton relate to tropical species and such spores have been recorded, among others, in South America [14], Asia [15,16], and Africa [17].
The annual counts of Pteridophyta spores that we recorded in Lublin over the 2-year study period (69,63) were similar to the annual sums of Polypodiaceae spores recorded in Rzeszów by K a s p r z y k [10] in 1999 and 2000, which were respectively 59 and 82.
The research on concentrations of airborne Pteridium aquilinum spores shows that the distance of the spore trap from clumps of spore-releasing plants and the height at which it is installed are of great importance. In their study conducted in Rothamstad in 1990 and 1991, L a c e y and M c C a r t n e y [8] located a spore trap in a field at a distance of about 20 cm from a clump of Pteridium aquilinum fronds. On some days of plant growth, they found the daily mean concentrations to be very high, since they exceeded 1.750 spores m - 3. However, an aerobiological study of bracken spores which was carried out under urban conditions of Edinburgh by C a u l t o n et al. [9] over the period 1988-1997 produced results that differed significantly from the data reported by the previous authors. In this case, the spore sampler was installed at a height of 21 m above ground level at a distance of about 1.6 km from the nearest sporing stand. The maximum concentration of Pteridium aquilinum spores recorded under these conditions in 1989, having a much higher spore count than in the other years, was only 4. The low concentrations of pteridophytic spores demonstrated in Lublin might have been associated with the location of the spore sampler on the roof of a high building around which no stands of Pteridiophyta were observed within a radius of 1 km.
Our study reveals that the pattern of the curves depicting the fern sporulation seasons in Lublin differs between 2013 and 2014. Other authors conducting research in Europe have also found that the length and timing of the sporing period vary between years [8,9]. CONCLUSIONS 1. Spores from 10 fern genera were recorded in aeroplankton of Lublin and most of them belonged to Dryopteris and Athyrium. 2. In both years of the study the most Pteridophyta spores in the air of Lublin were identified in August.