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We compared the capacity to accumulate airborne heavy metals of two lichens (Flavoparmelia caperata and Parmotrema chinense) and one higher plant (Nerium oleander) at a very densely populated urban site near Naples. After 15, 45, 75, and 120 days of exposure at four sites with different levels of air pollution, equal portions of thalli and 20 leaves were collected, and four environmentally significant elements, Fe, Cu, Zn, and Pb, were measured by inductively coupled plasma analysis. To compare the accumulation rates of lichens and the vascular plant, we determined an index of relative accumulation rate of pollutants during time and the ratio between the concentrations of each element in exposed samples to that of control samples (exposed-to-control ratio). Our data indicate F. caperata as being the most suitable bioaccumulator, followed by P. chinense. N. oleander was also found to be a useful heavy metal biomonitor though not suitable as a bioaccumulator.

Reproductive phenology, reproductive traits and the pre emergent reproductive success (PERS) of Welwitschia mirabilis were studied in plants growing in the Botanical Garden of Portici. The leaves grow throughout the year and growth is positively correlated to temperature and day length; at flowering, the growth rate slows down. The plants have a reproductive cycle lasting 9-10 months; male plants form more branches and strobili than females, female strobili are larger than male ones. Both male and female plants produce cones that differ in the color of the covering bracts. Plants produce a lot of seeds, but most of them are empty; therefore the seed/ovule ratio is low. Filled and empty seeds are morphologically similar; filled seeds have high vitality that is maintained for several years. As probable causes of the low seed/ovule ratio, both pollination and embryo abortion are taken into account; our observations lead us to believe that the embryo abortion hypothesis is more accurate. However, since each plant may produce a discrete number of cones and filled seeds are highly viable, ultimately Welwitschia appears to be a rather efficient plant in terms of pre emergent reproductive success.

Two plant growing methods, namely use of soil and a floating hydroponic system, were compared in order to determine whether the response of radish to Cd, Cu, Ni and Zn was affected by the cultural system. Seed germination, plant biomass (root, shoot, hypocotyl), and heavy metal accumulation in different parts of the radish plants were monitored. The presence of heavy metals in the germination medium had no effect on seed germination, while the biomass of plants grown in hydroponics was negatively affected by the presence of metals in the nutrient solution. In both cultural systems, the amount of metals in roots, hypocotyls and shoots increased significantly with the increasing metal concentration in the growth media; the highest concentrations of heavy metals were found in the roots. The bioconcentration factor (BCF) and translocation factor (TF) values for the four metals were found to be considerably different between both growing systems. The different responses of plants suggest that in contaminated soils the plants are in the presence of lower quantities of available metals than those found in the corresponding substrates of the hydroponic system.

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Cadmium (Cd) contamination is a severe problem in the environment and produces detrimental effects on crop productivity and quality. Characterization of crop performance at different Cd concentrations is crucial to identify pollution-safe cultivars with low translocation efficiency to aboveground organs to be used for food safety. Here, we estimated germination, survival, growth, photosynthetic pigments, Cd bioaccumulation, among-organs translocation, and ionic balance in six Solanum melongena L. (eggplant) cultivars from the central Mediterranean basin. On two cultivars, we also analyzed expression of genes involved in Cd uptake, i.e., heavy metal ATPases (HMAs) and metal tolerance proteins (MTPs). We found that Cd has a negative effect on all the investigated parameters but with relevant among-cultivar differences. Cd-treated plants showed a decrease in germination rate and survival. Photosynthetic pigments showed opposite trends, i.e., with increasing Cd contents, we observed a decrease in chlorophylls and an increase in carotenoids. The investigated cultivars showed high ability of sequestrating Cd in roots but a low translocation efficiency to the aboveground organs, suggesting a good potential for food safety. The response of plants to Cd was mediated by a different expression of the MTP and HMA gene families. Our study represents the first comprehensive investigation of Cd tolerance in eggplant varieties from the Mediterranean basin and highlights the importance of comparative studies to identify Cd-tolerant cultivars.

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