Acid mine drainage (AMD) endangers pomegranate trees nearby a copper mine.

Acid mine drainage (AMD) is known as an important source of environmental pollution with potentially toxic elements. High concentrations of minerals in soil were observed in a pomegranate garden nearby a copper mine, Chaharmahal and Bakhtiari, Iran. In the vicinity of this mine, AMD locally caused distinct chlorosis in pomegranate trees. As expected, potentially toxic concentrations of Cu, Fe, and Zn were accumulated in the leaves of the chlorotic pomegranate trees (YLP), i.e., increased by 69 %, 67 % and 56 %, respectively, compared to the non-chlorotic trees (GLP). Remarkably, also some other elements, including Al (82 %), Na (39 %), Si (87 %), and Sr (69 %) were considerably enhanced in YLP, compared to GLP. On the other hand, the foliar Mn concentration in YLP was strongly decreased, about 62 % lower than that in GLP. The most plausible reasons for chlorosis in YLP are either toxicity of Al, Cu, Fe, Na, and Zn, or a deficiency of Mn. In addition, AMD led to oxidative stress, shown by a high accumulation of H2O2 in YLP, and a strong upregulation of enzymatic and non-enzymatic antioxidants. AMD apparently caused chlorosis, reduced the size of individual leaves, and caused lipid peroxidation. A further analysis of the adverse effect of the responsible AMD component(s) could be helpful to reduce the risk of food chain contamination.

Effects of antimony on enzymatic and non-enzymatic antioxidants in a metallicolous and a non-metallicolous population of Salvia spinosa L.

The present study aimed at elucidating the role of antioxidants and stress metabolites in antimony (Sb) tolerance in a metallicolous (M), Sb[V]-hypertolerant population, and a non-metallicolous (NM) population of Salvia spinosa, particularly with regard to the question of whether they could be involved in constitutive Sb tolerance or, specifically, in Sb[V] hypertolerance in the M population. Plants were exposed in hydroponics to 0, 8, 24, 74, 221 µM Sb (Ш or V). Superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities, and the concentrations of phenolics, flavonoids, and proline in leaves were measured after 20 d. As potential stress/tolerance markers, the concentrations of chlorophyll a and b, anthocyanins, and those of total soluble and reducing sugars were also measured. Chlorophyll a concentration reflected the difference, both in Sb[III] and Sb[V] tolerance, between N and NM, and the higher toxicity of Sb[III], compared to Sb[V]. APX and proline accumulation were more induced in M than in NM, and more by Sb[V] than by Sb[III], which is theoretically compatible with a role in Sb[V] hypertolerance. CAT was more induced in M than in NM, but more by Sb[III] than Sb[V], suggesting that is not functional in Sb[V] hypertolerance. The other enzymes and compounds did not exhibit significant Sb redox status*population interactions, suggesting that they don't play a role in, specifically, Sb[V] hypertolerance in M, but at most in the constitutive Sb[III] or Sb[V] tolerance of the species.

Antioxidant potential in Stevia rebaudiana callus in response to polyethylene glycol, paclobutrazol and gibberellin treatments.

The study on Stevia callus has the potential to advance the knowledge of antioxidant mechanisms involved in unorganized cells response to drought stress. The effects of polyethylene glycol (PEG; 0 and 4% w/v) in combination with paclobutrazol (PBZ; 0 and 2 mg l-1) and gibberellin (GA; 0 and 2 mg l-1) were studied on Stevia rebaudiana callus. PEG treatment led to an oxidative stress, as indicated by increased H2O2 content whose accumulation was prevented with PBZ and GA treatments. All treatments of PEG, PBZ and GA increased the total antioxidant capacity, with the highest antioxidant power in PBZ and GA treatments without PEG. The activity of superoxide dismutase, catalase and ascorbate peroxidase significantly increased in PEG treatment alone or in combination with PBZ and GA. All treatments of PEG, PBZ and GA significantly increased proteins, amino acids and proline contents, with the highest increase in presence of PBZ in medium culture. In contrary to proline, the activity of pyrroline-5-carboxylate synthetase and proline dehydrogenase did not change in response to any of the treatments. Collectively, our results demonstrated that PBZ and GA increased reactive oxygen species scavenging and osmolytes in PEG-treated calli more than PEG treatment alone to alleviate negative effects of PEG on Stevia calli. These findings will enable us to design effective genetic engineering strategies in callus culture to generate some somaclonal variation that may be useful in enhancing drought resistance in Stevia.