G. Bartoli

Temporal and spatial variation in C, N, S and trace element contents in the leaves of Quercus ilex within the urban area of Naples.

This paper presents a comparative analysis of the concentrations of C, N and S and several trace elements (Fe, Mn, Na, Zn, Cu, V, Pb, Ni, Cr, Cd) in leaves of Quercus ilex, an evergreen oak, collected in the urban area of Naples in 1989 and 1996. The samplings were carried out from 25 urban sites (roads with different traffic flows as well as urban and suburban parks) and from two remote areas as controls. Relative to 1989, the values measured in 1996 denote a strong decrement of S, Fe, Na, Pb, and Cr, with the exception of S in control sites. By contrast, C, N and Cd contents were higher in 1996 than in 1989. Cu and Ni showed a conspicuous increment in control sites as well as in urban sites facing the sea and in the parks, while in all the other urban sites these elements decreased remarkably. No significant difference was found in the leaf contents of Mn, Zn and V measured in 1989 relative to 1996. Both in 1989 and 1996 the contents of N, S, Fe, Na, Cu, Pb, V, Ni, Cr and Cd were significantly higher in leaves from urban sites than in the controls, reflecting the high degree of contamination of the urban area. Concentration factors expressed as the ratio of road/control values for most of the elements were still very high in leaves collected in 1996, though remarkably lower than in 1989.

Effects of urban heavy metal pollution on organic matter decomposition in quercus ilex L. woods

Decomposition of oak (Quercus ilex) leaves containing different concentrations of Fe, Zn, Cu, Cr, Ni and Pb was measured in laboratory microcosms. The leaves were collected from a polluted site inside the city of Naples and from a control site away from the city. Soil was sampled from the upper A horizon (0–5 cm) at both sites and analyzed for respiration, microbial biomass and abundance of fungal mycelia. The soils from the two sites differed significantly in heavy metals concentrations. The accumulated mass loss reached an asymptotic value after four months both for the control and polluted litters. However, control and polluted litters significantly differed in accumulated mass loss, that was respectively 40 % and 29 % of the initial weight, after 10 months. Moreover decomposition rates appeared to be strongly influenced by metal contamination in the early stages, while in later stages, they did not differ significantly. Litter respiration appeared to be inhibited by metal contamination and showed pattern and rates consistent with those found for litter decomposition. Fungal mycelia were significantly less abundant both in litter and soil from the polluted site than from the control site. Metabolic activity (both as soil respiration and degree of mineralization) was lower in the polluted soil. Soil respiration and amount of soil mycelia correlated negatively with soil Pb, Zn and Cr concentration.

Leaf contamination by atmospheric pollutants as assessed by elemental analysis of leaf tissue, leaf surface deposit and soil

In order to evaluate the influence of air pollutants influx on leaf elemental composition, the concentration of N, S, Cu, Fe and Pb were analyzed in the surface deposit and tissue of Quercus ilex L. leaves from 8 sites of the urban area of Naples. The soil from the trunk base area of Q. ilex trees in the same sites was also analyzed for total contents of N and S and for available contents of Cu, Fe and Pb. In the leaf surface deposit S content was high though significantly (P <0.001) lower than in the leaf tissue, whilst N was not detectable. Cu, Pb and Fe contents in leaf surface deposit were conspicuous. The Pb content was higher in the leaf surface deposit than in the leaf tissue. No correlation between leaf tissue and surface deposit contents was found for S or for Fe. By contrast, positive and significant correlations (P<0.01) were found between leaf deposit and leaf tissue for both Cu and Pb. N and S contents in the leaves were not correlated to the respective contents in the soil and the same was also found for Cu and Fe. In contrast with the presence of limiting concentrations in the soil, N, S and Fe leaf contents were significantly higher than in the leaves from remote sites. The data suggest that direct uptake of airborne pollutants, in addition to root absorption, may influence leaf elemental composition of Q. ilex L. leaves.

TRACE METAL BIOMONITORING IN THE SOIL AND THE LEAVES OF QUERCUS ILEX IN THE URBAN AREA OF NAPLES

The concentrations of Pb, Cu, Fe, and Mn were analyzed in surface deposit and tissue ofQuercus ilex leaves from several sites of the urban area of Naples, exposed to different degrees of air pollution. These included some major roads with heavy traffic loads, squares, and three urban parks. The soil from the trunk base area ofQ. ilex trees in the same sites was also analyzed for total and available metal contents. Pb, Cu, and Fe contents in the surface deposit and leaf tissue were significantly higher (p<0.01) in leaves from roadside sites than in leaves from parks; significant correlations were found between deposit- and tissue-contents of Pb, Cu, and Fe. Mn content in leaves from roadside sites and in leaves from parks were similar and Mn content in the leaf deposit was irrelevant. Significant differences (p<0.001) in both total and available Pb and Cu soil content were found between sampling sites. Also for available Fe and Mn soil content differences among sites were relevant, although the highest values were measured in soil from urban parks. A positive correlation between leaf and soil metal content was found only for Pb, thus suggesting that trace metal contents of leaves directly depend on atmospheric depositions. Seasonal variations of Pb, Cu, and Fe were pronounced at a polluted site, whereas no relevant seasonal variation was observed at a control site; moreover, metal accumulation was high at the polluted site. Mn content and seasonal dynamics were comparable at control and polluted sites.

Crassulacean Acid Metabolism in Leaves and Stems of Cissus quadrangularis

The genus Cissus (Vitaceae) is found throughout both the wet and arid tropics of the world. Surveys of δ 13C values for plants collected in their natural habitats, as well as studies in controlled conditions (Schutte et al. 1967; Milburn et al. 1968; Virzo De Santo et al. 1978, 1980, 1983, 1987a; Ting et al. 1983; Olivares et al. 1984) suggest that CAM is a widespread feature in the genus Cissus that might have facilitated the spread of the genus from the wet into the arid tropics.

Gas exchange of two CAM species of the genus Cissus (vitaceae) differing in morphological features

Pattern and magnitude of stem gas exchange were studied under controlled conditions on two CAM species of the genus Cissus differing in morphological features. In the cactus-like liana Cissus quadrangularis, at water vapour deficit of the air (VPD) lower than 400 mPa Pa−1 during daytime, under 24/16°C and 27/16°C temperature regime, CO2 uptake occurred during daytime and nighttime but night fixation was responsible for 74 and 77% respectively of the CO2 fixed during the whole diurnal cycle; the contribution of night fixation increased up to 84% at VPD of 590 mPa Pa−1 under 27/15°C. In Cissus sp., a slightly succulent xerophytic liana with mesophytic deciduous leaves, at 27°C day temperature and VPD of 520–540 mPa Pa−1, under both 12 and 16°C night temperature, CO2 uptake occurred exclusively during the night; however at lower day temperatures (18–20°C) and lower VPD (169–269 mPa Pa−1) substantial CO2 uptake was observed in the light. Transpiration was higher in Cissus sp. than in Cissus quadrangularis under all of the conditions applied; moreover night transpiration in Cissus sp. contributed more to total day transpiration as compared with Cissus quadrangularis. The results support the opinion that the nocturnal gas exchange has a preeminent role in Cissus sp. as compared with Cissus quadrangularis. Indeed under conditions which enhance evaporative demand even well-watered plants of Cissus sp. resort totally to night fixation. In contrast Cissus quadrangularis which shows a larger resistance to water loss and possesses an abundant water storing parenchyma as compared with Cissus sp. resorts totally to night CO2 fixation only under drought stress.

Responses of Mentha piperita L. and Arabidopsis thaliana L. to fumigation with SO2 at different concentrations

Abstract Leaf necroses, chlorophyll destruction and sulphur accumulation followed from SO2 fumigation of Mentha piperita L. and Arabidopsis thaliana L. A SO2 dependent decrease in the cell sap pH occurred in both species, but A. thaliana showed a less effective buffering capacity as compared with M. piperita. Exposure to SO2 resulted in a decreased N content in H. piperita and in an increased N content in A. thaliana. M. piperita appeared to be able to remove SO2 from the air bringing about a pollutant sink.

Daily malate fluctuations in Sedum dasyphyllum L.

Abstract Sedum dasyphyllum L. leaves of well-watered plants kept outdoors and under controlled conditions show diurnal malic acid fluctuations. In well-watered plants growing outdoors the malate accumulation undergoes seasonal variations and seems to be inhibited by short photoperiod and/or by low temperature. The seasonal variations of CAM activity correspond to seasonal variations of mesophyll succulence. Water stress markedly depressed CAM activity. In fact, plants of S. dasyphyllum show, under controlled conditions, a decrease of malate accumulation as relative water content decreases. Recovery from water stress is fairly slow. Water potential quickly increases during rewatering and exceeds the original value after few days, suggesting a consumption of osmotic compounds during the water stress period.

Sulphur contamination of soil and Laurus nobilis L. leaves in the botanical garden of Naples University

Abstract The sulphur content in the leaves of Laurus nobilis L., and in soil was measured to estimate the level of SO2 pollution in the Botanical Garden of Naples University. Annual samples were taken during 1980, 1981, and 1982 at 10 locations to obtain an overall view of the incidence of urban pollution. The level of sulphur measured in leaves and soil differed significantly among locations and years. The amount of sulphur in the soil was correlated with the rainfall that preceded the annual sampling. Analyses of leaf chlorophyll and nitrogen content showed that the levels of chlorophyll and nitrogen decrease as the amount of sulphur in the leaf increases, thereby confirming that SO2 has an unfavourable effect on plant metabolism.