Histochemical Properties and Trace Element Concentrations in Parietaria L

Aerobiologia (2005) 21:21–31 Ó Springer 2005 DOI 10.1007/s10453-004-5873-6

Original paper Histochemical properties and trace element concentrations in Parietaria L. from urban sites (Palermo, Italy)

Maria Grazia Alaimo, Daniela Vizzı` & Maria Rita Melati* Department of Botanical Science, University of Palermo, Via Archiraﬁ 38, 90123, Palermo, Italy (*Author for correspondence: Phone: +39-091-6238229; Fax: +39-091-6238203; E-mail: [email protected])

(Received 22 October 2003; accepted 21 September 2004)

Key words: histochemistry, trace elements, pollution, Palermo, Parietaria L.

Abstract

We examined leaf and pollen histochemical properties in Parietaria L. and measured trace element concentrations in urban sites in Palermo, Sicily, affected by different stress valence levels. Urban pollution affects histochemistry macro-, micro-, and toxic element concentrations in Parietaria. We therefore decided to determine whether this plant can be used as a simple biomonitor or bioaccumulator of pollution contaminants. Samples were collected at various sites in different periods. An increase in phenolic compound levels was a result of the impact of pollution. Histochemical characteristics and trace element concentrations varied according to the period, but not to the place, of sampling. Pollutant concentrations were the highest in the month of February 2002. Trace metal concentrations were the lowest in July. Our investigations have confirmed that Parietaria L. can be used to study the effects of trace elements in the atmosphere in urban sites; in fact, they are veritable accumulators, given that elevated levels of pollutants can be found on their structures with no visible morphological effects. There are differences in accumulation capacity according to the trace elements studied. Pollution alters the content of phenolic compounds and chemical elements in Parietaria L.

1. Introduction in plants, and of pollen allergies in human beings. Many air pollutants enhance allergic reaction, In the ambient air, allergen carriers, such as playing a role in the development of sensitisation pollen grains and leaves, incorporate pollutants (e.g. diesel exhaust particles) and in increasing the from the atmosphere, resulting in alterations in the response in already sensitised organisms pollen surface and in protein and allergen release, (D’Amato, 1999, 2000). and causing cell modifications in leaves (Alaimo We need able to differentiate air pollution et al., 2000a; Lombardo et al., 2001). patterns in order to determine the ecotoxicological Leaves and pollen grains, which are a major effects they have on allergies. Fine and ultrafine source of outdoor aeroallergens, interact with air particles containing trace metals have been linked pollutants; pollen grains collected from sites with to stronger ecotoxicological effects and increased heavy traffic contained agglomerates of airborne incidences of allergic sensitisation and disease particles. Qualitative histochemical staining (Bricchi and Mincigrucci, 1999). revealed some histochemical modifications and ‘‘Ecotoxicology’’ can be used as a research metabolite accumulation in the leaves (Gahan, framework to study the impact of environmental 1984; Alaimo et al., 1998). pollutants (toxic substances) on the onset In fact, phenol content is positively correlated and perpetuation of accumulation phenomena with toxic elements, a finding which is confirmed 22 in literature (Zobel and Nighswander, 1991; Sampling was conducted in February 1997 and, Giertych et al., 1997, 1999; Alaimo et al., 2000b). for the sake of comparison, in July 2001 and There is increasing evidence that various February 2002. Samples were more numerous in environmental factors influence accumulation July in order to have more information or con- phenomena in many plants (Katoh et al., 1989)– trols. Samples were collected from around the including common herbaceous plants such as perimeter of the plants, and stored in paper bags. Parietaria judaica L. (Melati et al., 1997; Melati The sites sampled in February 1997 were Via and Alaimo, 1999; Alaimo et al., 2001a, b) – and Emilia (VEP), urban site with light traffic; Via affect the development of allergies. Ingegneros (VIP) = urban site with light traffic, Nevertheless, while the role of environmental light vehicles; O. Cervello (HCP) = periurban site pollutants in allergies is still controversial, we have with very heavy traffic, near the Palermo–Trapani a great amount of data on trace element accumu- motorway. lation in plants and on bioindicator and bioaccu- The urban and periurban (remote) sites re- mulator plants that can usefully be compared ported in July 2001 and February 2002 periods are (Posthumus, 1976; Manning and Feder, 1980). not the same as those in February 1997, yet they Urticaceae are arboreal and herbaceous plants, are more or less comparable. and comprise many different species. Of particular The following sites, situated in different areas interest for allergology studies are the species be- of the city of Palermo and affected by various longing to the Parietaria genera, which mainly types of emissions, were selected: Foro Italico, grow around ruins, in dry soil conditions, and on Ponte Ammiraglio, via Leonardo da Vinci (FIP, wasteland and walls. PAP, PLVD) are sites with both passenger car and Pollen counts are highest when the climate is commercial vehicle traffic; Via Crispi, Via dry and hot, and pollen production continues Imperatore Federico, Teatro della Verdura, Piazza from the early hours of the morning until the Principe di Camporeale, via delle Alpi (VCP, IFP, afternoon. In the South (see Palermo, Sicily) FIP, TVP, PCP, VAP), are sites with light traffic; pollination periods are becoming longer and high via Montepellegrino, villa Trabia (MPP, TBP), concentrations of pollen are found all year relatively far from any anthropogenic sources, round (Melati et al., 1997). Pollen allergies are were selected as reference sites, as Orto Botanico e more common in April. Pollen vitality is the Borgo marinaro di Sferracavallo (OBP, PLSF), highest in late spring and at the beginning of clean sites, relatively far from traffic. autumn, and is undoubtedly affected by me- FIP = urban site, east; VCP = urban site teorological conditions such as rainfall, tem- (port), north-east; MPP = urban site, north; IF- perature, periods of drought and pollution P = urban site, north/north-west; TVP = urban (Franchi et al., 1984) site (city suburbs) west/south-west; PCP = urban The aim of this research is to detect the pre- station, west; VAP = urban site, west/north-west; sence of trace elements from anthropogenic sour- TBP = urban site (park) west; PAP = urban site ces and determine their impact on Parietaria,a (city suburbs) east; OBP = urban site (garden), common vascular plant in urban sites, in order to east; PLSF = periurban site (seaside village) west; evaluate and correlate leaf and pollen histochem- PLDV = urban site south. ical changes with macro-, micro-element or other Leaves and pollens were taken randomly from metal content. Our investigations were conducted all the plant’s exposures. Fully-grown leaves in 1997 and 2001–2002. growing at some distance from the most recent germination rings (July 2001–February 2002) and 2. Materials and methods complete inflorescences were selected. The leaf and pollen samples were treated for 2.1. Leaves and pollens histochemical and chemical analyses. The biological analyses began with an assess- Samples of Parietaria judaica L. were collected at ment of morphological characteristics, carried out several urban and periurban sites in Palermo in situ during sampling. (Sicily), affected by different environmental stress Pollen was taken from the flowers of plants conditions. growing in sites with heavy traffic and divided into 23 three batches: one for structural observations (Cu), Manganese (Mn), Zinc (Zn). Blanks were (with Leica Orthoplan optical microscope); an- systematically measured, and results were always other for histochemical observations on cryosec- negligible as regards total amount of lead (Lead tions (with Leica cryostat) of unfixed stamens; the (Pb)) in the samples. third for leaf tissue diaphanization with NaOH All tests on both standards and samples were (5%) and stereomicroscopy trichome observa- repeated three times to minimise the risk of errors. tions. A part of each sample collected in 2001 and Each batch consisted of at least 10 samples of 2002 was analysed for major and trace elements different age. Tests were repeated five times. using instrumental neutron activation analysis Later, in the laboratory, the leaves and in- INAA (Barium (Ba), Bromine (Br), Calcium (Ca), florescences were cryosectioned at the proximal Chrome (Cr), Iron (Fe), Potassium (K), and distal portions and stained with 0.08% Fast Molybdenum (Mo), Sodium (Na), Antimony (Sb), Blue BB solution, at pH 6.5 in 0.2 acetate buffer; Scandium (Sc), Samarium (Sm)) and ICP-MS they were incubated at room temperature for (Aluminium (Al), Magnesium (Mg), Phosphorus 30 min to assess polyphenols following the (P), Sr, Manganese (Mn), Copper (Cu), Lead (Pb), Gahan’s test, (Gahan, 1984). Zinc (Zn)) with the standards NBS 1572 and 1632 Red–brown deposits indicate polyphenols, ab- B for reference. Several replicates yielded a preci- sent in the controls collected in clean sites. sion of 20–30% for minor elements and 5–10% for Other wholeleaf bladesfrom the same batchwere major elements. (Activation Laboratories Ltd., cleaned with 5% sodium hydroxide solution and Ont., Canada), (Alaimo et al., 2000b). Con- household bleach and stained with 1% safranin or centrations are expressed in ppm or ug/g of dry fuxine, according to Klucking’s protocol (Klucking, weight (Soto Gonzales et al., 1996). The tests were 1988). A stereomicroscope (Leica MZ75) was used repeated five times. On account of biological, to count hairs on the blades. chemical and physical variables, homogeneous within each class, but non-homogeneous between 2.2. Determining trace elements classes, we did not subject the data to parametrical statistical analysis, but to observations to map the Chemical analyses were carried out on Parietaria presence or absence of plant injury. Given the unwashed leaves (collected in February 1997 and, uniformity of the findings, also when compared to for the sake of comparison, in July 2001 and our previous observations, we did not resort to February 2002) and pollens (collected in February sequential plans which would have provided 1997). unequivocal evidence of the correlation between Accurately weighed quantities of leaves or pollution and the injuries we found. pollens (0.5 g), previously furnace-dried at a temperature of 80 °C for leaves and 34 °C for pollen 3. Results for one night, were reduced to very small frag- ments with an ordinary mill. Leaves and pollen The following injuries were observed in Parietaria were treated with 6 ml of HNO3 at 65% (RPE plants Carlo Erba, Milan) and 1 ml of H2O2 at 30% (a) structural injuries: necrotic tips in leaf lamina, (RPE Carlo Erba, Milan) and put in a microwave pollen browning, mesophyll thickness coarcta- mineralizer (Milestone MLS-1200 Mega) con- tion nected to a unit which prevents vapour stagnation (b) consequential histochemical changes: poly- inside the furnace. This mineralizer model supplies phenol accumulations in leaves and pollen non-pulsed power, allowing an excellent control of There are no significant morphological lesions the oxidization processes of organic samples. in the leaves; pollens are not particularly coarc- Distilled water is added to bring the clear solutions tated or deformed, nor is the exine split (Figure 1). to volume, now free of organic substances. Ana- Microscope observations reveal a tendency to- lyses were carried out with an atomic absorption wards sclerophylly, polyphenol accumulation and spectrometer (Perkin Elmer mod. 3100) with gra- increase in the number of hairs. phite oven atomisation (for Lead (Pb)) and flame These modifications are more pronounced in atomisation (Perkin Elmer HGA 600) for Copper samples from urban sites, where plants are 24

Figure 1. Morphology of some pollen samples (a,b,c) stained in gelatine with fuxine. Pollens were monitored of an urban station in Palermo. The aereobiological investigation was carried out using Lanzoni VPPS 2000 type volumetric pollen trap (Hirst, 1952). The Parietaria pollen was most abundant in Palermo.

exposed to higher levels of pollutants (Figures 2a– c). We carried out a chemical-analytical evaluation of trace elements in pollen and leaves with more extensive stress-induced injuries and compared them to trace element content in samples from other urban stations or urban stations with lower levels of traffic and household heating pollution. The characteristic polyphenol accumulations in the mesophyll cells of the leaves and in the pollen exine are, qualitatively speaking, more con- spicuous in samples collected in winter (February 2002) (Figure 3). Figures 4a, b and 5a, b present a summary of trace element concentrations in leaf samples of Parietaria in various areas of the city of Palermo. The results reported in Tables 1 and 2 are expressed in ppm of dry weight. Leaf chemical element content in summer and in winter differs. Figure 2. Cryosections of the apical portion of the leaf polluted Copper (Cu), Lead (Pb), Manganese (Mn), Phos- (b,c) and control (a) of Parietaria. Photos b, c show phenols staining as red or dark brown precipitate and the colour is phorus (P) and Zinc (Zn) levels are decidedly lower intense while the control (a, OBP site, February 2002) is low- in summer (2001–2002). Aluminium (Al) and stained. Sample b is an intermediate case (PLSF site, February Magnesium (Mg) levels are higher in the summer 2002). The mesophyll cells are not deformed but in polluted (2001–2002). samples (FIP site, February 2002) it is possible to notice the reaction to pollutant stress in the form of cell necroses. Table 1 presents a summary of trace element concentrations in samples of pollen (February, 1997) and, for the sake of comparison, also in leaves and inflorescences. Table 2 presents a sists, and that its effects are apparent in plant or- summary of trace element concentrations in leaf ganisms. Lead (Pb) and Iron (Fe) concentration samples (July 2001 and February 2002), average levels are higher in winter 2002 than in the sum- values and standard deviation. The results mer, but are still lower than levels recorded in reported in Tables 1 and 2 are seasonal averages other plants we have studied (Cupressus, Ficus, and are expressed in ppm of dry weight. This nerium, Pinus, Platanus, Quercus, etc.), while research confirms that trace metal pollution per- Chrome (Cr) levels, for instance, were lower in 25

summer) (Mn, winter, summer) (Zn, winter, summer). At the periurban site of Sferracavallo (PLSF), concentration levels, of Lead (Pb) for example, are higher than levels recorded at the Botanical Garden (OBP) site. At the Ponte Ammiraglio (PAP) site, a suburban street with a lot of traffic, we recorded medium-high concentration levels in winter (for Lead and Zinc, for example) and low levels in summer (for example, for Molybdenum, Lead and Manganese). No differences in leaf trace element content between polluted and unpolluted sites were noted. Lead Figure 3. Morphology of red stained pollens for phenols test (Pb), Manganese (Mn) and Copper (Cu) levels are (February 2002) (FIP site). lower in summer than in winter. Lead (Pb) levels range from 11 to 48 ppm (in the winter) and 2 to winter. This study demonstrates that there are 20 ppm (in the summer). differences in Parietaria capacity regarding the Copper (Cu) levels range from 11 to 44 ppm (in macro–micro and toxic elements (trace elements) the winter) and 8 to 28 ppm (in the summer). studied. Accumulation concentration levels of Manganese (Mn) levels range from 27 to some macro-elements, such as Calcium (Ca), So- 65 ppm in the winter and 21 to 42 ppm in the dium (Na) levels are higher in winter. Concentra- summer. tions levels of all microelements except Bromine (Br), Antimony (Sb), Zinc (Zn) and Molybdenum (Mo) are higher in the winter. The Copper (Cu), which are anthropogenic, were highest levels of Lead (Pb) were found when found in the following concentrations: Br, temperature and humidity were low. 26–220 ppm (in the winter) and 36–300 ppm (in the At the periurban site of Via Montepellegrino summer); Sb, 0.97–2.1 ppm (in the winter) and (MPP), for example, Manganese (Mn) levels rise 0.5–4.3 ppm (in the summer); Zn, 40–126 ppm (in from 27 ppm in summer to 43 ppm in winter, and the winter) and 25–64 ppm (in the summer). at the remote site of Sferracavallo (PLSF) the Copper (Cu) levels are above the natural levels winter level is 41 ppm. At the central urban site (2–20 ppm). Zinc (Zn) concentrations are often of via Crispi (VCP) Lead (Pb) levels rise from above 20 ppm (Kabata-Pendias and Pendias, 5 ppm in summer 2001 to 31 ppm in winter 2002 1993). Allen et al., (1974) established normal and at the Ponte Ammiraglio (PAP) site, an natural lead levels in plants to be about 3 ppm. urban station with a lot of traffic, levels reach Compared to the controls, we observed an 31 ppm in winter. At the Botanical Garden site, increase in phenolic compounds in the leaf cryo- summer 2001 and winter 2002 Lead (Pb) levels sections, as a result of pollution impact. are identical:11 ppm. In unpolluted sites (such as We recognise the role of phenols as biological TBP, villa Trabia), at some distance from busy indicators of pollution. Stress conditions make roads, total concentrations of Lead (Pb) are higher energy demands on a plant, and the ele- relatively low. No differences in leaf trace element vated presence of phenols is a consequence of this. content between polluted and unpolluted sites Increased phenol production is part of the plant’s were noted. defence mechanism. Leaf concentrations at the control and at the The figures show diffuse phenol staining in the polluted sites are similar: Iron (Fe) and Manga- leaves. Chemical concentration is heavier where nese (Mn) levels, for example, are comparable. the colour is more intense, a factor which is always However, levels of Copper (Cu) (winter, summer), related to higher levels of pollutants. An increase Manganese (Mn) (winter, summer), Zinc (winter) in phenols precedes the appearance of macro- and Lead (Pb) (winter, summer) are low at the scopically visible damage. Phenols are considered Botanical Garden (OBP) site, while concentra- important biomarkers of the phytotoxic effects tions of almost all the elements in all seasons are that heavy metals and other pollutants may have high at the Foro Italico (FIP) site (Cu, winter, on plants. 26

Figure 4. (a) Macro-element concentrations in Parietaria judaica L. leaves of diﬀerent polluted or not polluted sites (July 2001). Data are in ppm (dry weight). (b) Micro-element concentrations in Parietaria judaica L. leaves of diﬀerent polluted or not polluted sites (July 2001). Data are in ppm (dry weight). Bars = 100 lm. 27

Figure 5. (a) Macro-element concentrations in Parietaria judaica L. leaves of diﬀerent polluted or not polluted sites (February 2002). Data are in ppm (dry weight). (b) Micro-element concentrations in Parietaria judaica L. leaves of diﬀerent polluted or not polluted sites (February 2002). Data are in ppm (dry weight). Bars = 100 lm. 28

Table 1. Trace element concentrations in Parietaria judaica L. leaves, pollens and inﬂorescences of diﬀerent polluted sites (February, 1997)

Stations Samples of Pb (ppm) Cu (ppm) Cd (ppm) Mn (ppm) Zn (ppm) Fe (ppm) Parietaria

VEP1 Pollens 10.40 119.00 0.562 93.80 78.00 973.00 VEP2 Leaves 0.59 22.80 0.04 27.40 49.00 387.00 VIP1 Pollens 10.00 114.30 1.33 90.16 75.00 926.60 VIP2 Leaves 0.60 6.86 0.08 5.41 4.50 55.60 HCP1 Pollens 44.18 69.80 0.078 93.00 159.00 1434.00 HCP2 Leaves 0.81 34.50 0.00 45.70 46.00 129.00 HCP3 Inﬂorescences 30.00 47.00 0.040 63.40 108.40 977.70

VP1, VEP2 = Via Emilia; VIP1, VIP2 = Via Ingegneros; HCP1, HCP2, HCP3 = Ospedale Cervello. The trace elements were measured using atomic absorpion specrophotometer with graphite furnace or by INAA or ICP-MS.

4. Discussion from the environment. Our observations have shown that Parietaria is a useful biomonitor, and Parietaria L. species are widespread in urban and that it has all the characteristics of a typical periurban areas of Palermo. They act as passive bioaccumulator, tolerant of the various environ- phytoaccumulators as they absorb contaminants mental stress conditions that are present in the city without undergoing any morphological alterations. of Palermo. The leaf and pollen structure and histochemical Parietaria plants grow in many of the urban characteristics of Parietaria were examined by and periurban sites that were randomly chosen for conventional light microscopy. With atomic our investigations; they do not require any parti- absorption spectroscopy, we measured accumula- cular care, are always vegetative and have a tions of trace elements, which adhere to atmo- lengthy pollen production period. The leaf histo- spheric particulate, in leaves and, in a previous chemical findings and few injuries revealed during study (Melati et al., 1997), in pollen samples col- these investigations are very likely a sign of aerial lected in different sites with heavy motor traffic. pollution from trace elements (see hyperproduc- Both the pollen and the leaf samples contained tion of phenols and surface hairs). Pollutant con- high concentrations of trace elements. These data centrations were higher in February 2002 (winter prompt us to class Parietaria as an accumulator of sampling period) than in July 2001 (summer pollutants, with a specific environmental role sampling period), which can be attributed to the (Wolterbeek, 2002). Moreover, an examination of use of household heating and a climate that does cell structure reveals that Parietaria plants are not not favour dispersal rather than to a mere accu- very susceptible to pollutants. Like in all optimal mulation effect. In a previous study of N. oleander bioaccumulators, the morphology and mesophyll L., which was sampled in July 2001, February structure of leaves from both clean and polluted 2002 and July 2002, we reported that trace element sites is unaffected; apart from a coarctation in concentrations were lower in the July 2002 sample mesophyll thickness, the only explicit sign that an than in the February 2002 sample (Alaimo et al., adaptive defence mechanism against environ- 2001a, b, 2003; Melati et al., 2001), which excludes mental stress has been set in motion is an unusual the hypothesis that pollutants merely accumulate polyphenol accumulation (Strack et al., 1998). We layer by layer on the leaves; instead, this suggests a propose to refer to ‘‘Ecotoxicology’’ as a field that dynamic process of capture trace elements from studies and groups together allergenic plants, and the atmosphere. Pollen injuries also related to the all other plants which accumulate the various accumulation of pollutants on the pollen and to toxic elements present in the environment. pollen blackening, were more apparent in the Parietaria, although its being a highly allergenic winter period samples (February 1997, 2002). The plant, has its important ecological role as a higher incidence of allergies recorded around April bioaccumulator capable of capturing pollutants can be linked to this higher winter accumulation of Table 2. Summary for Parietaria judaica leaves trace-elements and microelements concentrations with different polluted or not polluted sites, showing summer (July 2001) and winter (February 2002) values and mean squares (media). Data are in ppm (dry weight):ppm = (mg/kg of dry weight).– = below instrument detection limit

Elements Sampling (July 2001) Media Standard Sampling (February 2002) Media Standard

FIP VCP MPP IFP TVP PCP VAP TBP PAP OBP PLSF PLDV PAP POB FIP

Al 4000 500 2900 1400 600 2400 6000 4500 5000 1700 2662.40 2028.96 300 600 500 200 800 480 38.74 As––– –––––– –– – 1.41.50.68 0.3 0.18 0.80 0.61 Au 26.6 4.4 9.6 5.2 31.9 33.8 3.7 9.8 11.5 18 15.45 11.47 10.5 32.7 9.8 7.7 5.4 13.22 11.07 Ba – 57 45 – – 25 45 – – 110 56.4 32.09 63 45 – 32 37 44.29 13.59 Br 150 43 52 57 69 69 36 300 47 58 88.10 88.01 64 26 150 27 220 97.40 85.09 Ca 88,000 92,000 103,000 99,000 97,000 58,000 84,000 69,000 100,000 86,000 87,000.60 14,400.61 112,000 95,300 67,100 79,300 88,600 88,460.00 16,890.00 Cr 9.5 6.5 4.5 3.6 4.5 3.8 3.1 0.5 0.5 3.5 4.00 2.64 5.9 4.5 2.1 1.3 4.1 3.58 1.86 Cu 28 15 16 19 14 12 11 11 8 13 14.70 5.57 15 44 39 11 33 38.40 14.65 Fe 1220 650 820 630 720 380 420 570 620 950 728.00 123.44 600 1400 1100 400 200 740.00 497.99 K 12,000 15,000 12,000 13,000 16,000 17,000 22,000 11,000 15,000 28,000 16,100.00 5258.85 17,000 3000 2000 2000 2000 5200.00 6610.59 La 0.97 0.42 0.86 0.52 0.59 0.6 0.27 0.47 0.51 0.93 0.61 0.23 0.43 0.48 0.41 0.25 0.67 0.44 0.15 Mg 11,500 14,200 12,700 8700 21,500 8200 6700 24,600 23,600 7400 13,910.00 6890.00 13,500 9300 13,600 11,500 12,300 12,040.00 1762.95 Mn 42 21 56 28 33 34 34 35 27 29 33,90 9.59 41 61 43 27 65 47.40 15.58 Mo 4.7 2.5 3 2.3 1.1 2.2 – 4.4 8.6 10 4.2 3.5 – – 1 1.6 – 1.3 0.42 Na 5280 1900 2910 2650 1020 1890 1190 3520 2940 1590 2489.00 1274.47 6200 5400 6300 2600 8100 5720.10 204.24 P 1850 1940 1770 1770 1720 1400 1790 1420 1780 1550 1699.00 181.25 1590 3460 3220 1820 1930 2404.00 867.36 Pb205929–4–– 118.57 5.96 19 21 31 11 48 26.00 14.21 Sb 4.3 0.93 2 1.4 1.3 1.1 0.87 0.34 0.5 1.4 1.41 1.12 1.6 2 1.6 0.97 2.1 1.65 0.44 Sc 0.26 0.14 0.19 0.15 0.17 0.16 0.14 0.12 0.16 0.23 0.16 0.04 0.13 0.14 0.07 0.04 0.1 0.09 0.04 Sm 0.14 0.065 0.11 0.068 0.045 0.062 0.065 0.056 0.083 0.11 0.08 0.03 0.045 0.067 0.05 0.023 - 0.04 0.01 Sr 200 140 180 170 160 120 15 200 280 260 172.50 74.20 258 200 258 309 200 245.00 46.05 Zn 54 52 64 43 41 28 32 25 34 52 42.5 12.80 56 126 73 40 74 73.8 32.34

The samples were dried for 48 h at 40 °C and then ground to a fine powder. Then samples were analysed by INAA and ICP-MS. FIP = Foro Italico; VCP = Via Crispi; MPP = Via Montepellegrino; IFP = Via Imperatore Federico; TVP = Teatro della Verdura; PCP = P.zza Principe di Camporeale; VAP = Via delle Alpi; TBP = Villa Trabia; PAP = Ponte Ammiraglio; OBP = Orto Botanico; PLSF = Sferracavallo; PLDV = Via Leonardo da Vinci. 29 30 pollutants. Towards October, it is rare to see of the process that protects the plant against pol- patients with allergy symptoms even though pollen lutants. vitality is high, probably because pollutant ag- The hyperproduction of secondary metabolites gregation on the pollen is decreasing. In fact, is part of the plant’s mechanism to repair stress- pollutant levels were already lower by summer induced injuries through processes of detoxifica- (July) than at the end of winter. tion. In stress conditions, secondary metabolites One source of emission of trace elements such stabilise cell membranes because they probably as Lead (Pb), Nickel (Ni), Cadmium (Cd), Man- enter the membrane lipid double layer, increasing ganese (Mn) and Zinc (Zn) is traffic. Cadmium hydrophobic cohesion between the two layers, and (Cd) and Zinc (Zn) are used as alloys in motor thus preventing the membranes from disintegrat- vehicle accumulators or in carburettors (Bereket ing due to stress events. This study was carried out and Yucel, 1990). They are released into the at- from the typical observational perspective of the mosphere during combustion. Parietaria leaves plant biologist–aerobiologist, with confirmation of turn out to be modified to a lesser extent when analytical data compared with morphological data levels of Aluminium (Al), Magnesium (Mg) and (integrated type of research). Natrium (Na) are higher and the temperature is higher; more damage is observed when Copper Acknowledgements (Cu), Manganese (Mn), Phosphorus (P), Lead (Pb) and Zinc (Zn) levels are lower and temperatures This work was funded by the Ministry for are colder. the University and Scientific and Technological It is a fact that some trace elements may be Research (MURST 60%) and by the Sicilian absorbed (Haghiri, 1973). Zinc (Zn) and Copper Regional Government. (Cu) penetrate at least partly into the leaf (Little and Martin, 1972). If Lead (Pb) salts are deposited References onto the plant surface in an insoluble form, they probably remain on the outside of the epidermis Alaimo M.G., Palmeri E., Bruno A. and Melati M.R.: 1998, (Smith, 1971). If they are deposited in a soluble Proposal for the evaluation of stress caused by environ- form, or are rendered soluble after impact, they mental pollution with plant markers. Sixth International Congress on Aerobiology Perugia 31 Agosto-5 Settembre. are probably taken into the plant through stomata Alaimo M.G., Lipani B., Lombardo M., Orecchio S., Turano and other openings or can penetrate the cuticle and Melati M.R.: 2000a, The mapping of stress by lead (Arvik and Zimdahl, 1974). However, penetration dosage in the predominant plants of Palermo Italy. Int. J. Aerobiol. 16, 47–54. Turano M. seems to be dependent on plant species (Krause Alaimo M.G., Dongarra` G., Melati M.R., Monna F. and and Kaiser, 1977). Barrica D.: 2000b, Recognition of environmental trace metal contamination using pine needles as bioindicators–the urban area of Palermo (Italy). Environ. Geol. 39 (8), 914–924. 5. Conclusions Alaimo M.G., De Vita F., Firetto A., Robba L., Vizzı` D. and Melati M.R.: 2001a, Different tendency towards sclerophylly This study proves that phenolic compound content of leaves from plants found in urban and suburban areas of Palermo. X Optima Meeting. 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