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 con- centrations 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 com- pound 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