Heavy Metals Bioindication Potential of the Common Weeds Senecio vulgaris L., Polygonum aviculare L. and Poa annua L.

Abstract

In recent years, heavy metals (HMs) levels in soil and vegetation have increased considerably due to traffic pollution. These pollutants can be taken up from the soil through the root system. The ability of plants to accumulate HMs into their tissues can therefore be used to monitor soil pollution. The aim of this study was to test the ruderal species Senecio vulgaris L., Polygonum aviculare L., and Poa annua L., as possible candidates for biomonitoring Cu, Zn, Cd, Cr, Ni and Pb in multiple environments. The soils analyzed in this work came from three different environments (urban, woodland, and ultramafic), and therefore deeply differed for their metal content, texture, pH, and organic matter (OM) content. All urban soils were characterized by high OM content and presence of anthropogenic metals like Pb, Zn, Cd, and Cu. Woodland soils were sandy and characterized by low metal content and low OM content, and ultramafic soils had high Ni and Cr content. This soil variability affected the bioindication properties of the three studied species, leading to the exclusion of most metals (Zn, Cu, Cr, Cd, and Pb) and one species (P. aviculare) due to the lack of linear relations between metal in soil and metal in plants. Senecio vulgaris and Poa annua, conversely, appeared to be good indicators of Ni in all the soils tested. A high linear correlation between total Ni in soil and Ni concentration in P. annua shoots (R2 = 0.78) was found and similar results were achieved for S. vulgaris (R2 = 0.88).

Production of Antioxidant Molecules in Polygonum aviculare (L.) and Senecio vulgaris (L.) under Metal Stress: A Possible Tool in the Evaluation of Plant Metal Tolerance

“…Our results pointed out that the amounts of the six tested metals, detected in the shoots of both species, were directly proportional to their concentration in the hydroponic culture media ( Figure 1 and Figure 2 ). As a consequence of this proportional absorption, the studied species could be considered good indicator plants, confirming previous results that proved S. vulgaris to be a viable Ni indicator in different soil environments [ 29 ]. According to the present data, P. aviculare was more efficient than S. vulgaris in preventing metal absorption, going towards an excluder behavior, especially in the presence of Cd and Pb.…”

“…Similar results are usually unachievable when these plants are cultivated in the soil, where metals are less bioavailable. In fact, data on P. aviculare and S. vulgaris collected from natural soils showed that these species were not capable of concentrating HMs in the shoots, having in most cases BAFs below 0.3 [ 29 ].…”

“…For both plant species, five different populations were collected from five different locations: Bologna urban area (B), Bologna woodland area (N), Milano urban area (M), Milano woodland area (T) and Mt. Prinzera serpentine area (P), following the sampling plan as in Salinitro et al [ 29 ].…”

“…These populations are adapted to different soil heavy metal (HM) levels: the two urban populations (B and M) are adapted to high levels of several HMs, especially Zn, Cu and Pb; the Mt. Prinzera serpentine population (P) tolerates high levels of Ni and Cr; and the two woodland populations (N and T) are adapted to low-HM soil [ 29 ].…”

“…For treatment A, the total concentration of each metal corresponded to that found in urban soils [ 29 ]. These values were multiplied by different factors (e.g., for Zn by 2, 4 and 10), according to the toxicity of each element up to concentration D, the maximum still allowing plant growth and development.…”