Cadmium-Induced Changes in Antioxidative Systems, Hydrogen Peroxide Content, and Differentiation in Scots Pine Roots

Abstract

To investigate whether Cd induces common plant defense pathways or unspecific necrosis, the temporal sequence of physiological reactions, including hydrogen peroxide (H 2 O 2 ) production, changes in ascorbate-glutathione-related antioxidant systems, secondary metabolism (peroxidases, phenolics, and lignification), and developmental changes, was characterized in roots of hydroponically grown Scots pine (Pinus sylvestris) seedlings. Cd (50 m, 6 h) initially increased superoxide dismutase, inhibited the systems involved in H 2 O 2 removal (glutathione/glutathione reductase, catalase [CAT], and ascorbate peroxidase [APX]), and caused H 2 O 2 accumulation. Elongation of the roots was completely inhibited within 12 h. After 24 h, glutathione reductase activities recovered to control levels; APX and CAT were stimulated by factors of 5.5 and 1.5. Cell death was increased. After 48 h, nonspecific peroxidases and lignification were increased, and APX and CAT activities were decreased. Histochemical analysis showed that soluble phenolics accumulated in the cytosol of Cd-treated roots but lignification was confined to newly formed protoxylem elements, which were found in the region of the root tip that normally constitutes the elongation zone. Roots exposed to 5 m Cd showed less pronounced responses and only a small decrease in the elongation rate. These results suggest that in cells challenged by Cd at concentrations exceeding the detoxification capacity, H 2 O 2 accumulated because of an imbalance of redox systems. This, in turn, may have triggered the developmental program leading to xylogenesis. In conclusion, Cd did not cause necrotic injury in root tips but appeared to expedite differentiation, thus leading to accelerated aging.

Up-regulation of antioxidant and glyoxalase systems by exogenous glycinebetaine and proline in mung bean confer tolerance to cadmium stress

“…The biosynthetic capacity of AsA is impaired under severe stress conditions because the AsA pool is generally determined by its rates of not only regeneration but also synthesis (Song et al 2005). It has been reported that regeneration of AsA under Cd stress is insufficient or that AsA synthesis is lower than AsA catabolism (Schützendübel et al 2001(Schützendübel et al , 2002Chao et al 2010). Importantly, both proline and betaine-supplemented seedlings maintained significantly higher AsA content as compared to the seedling treated Cd alone.…”

Zinc-Finger Transcription Factor ZAT6 Positively Regulates Cadmium Tolerance through the Glutathione-Dependent Pathway in Arabidopsis

“…Cd has been demonstrated to inactivate or denature proteins by binding to sulfhydryl groups, which causes cellular damages by displacing cofactors from a variety of proteins, including transcription factors and enzymes (Goyer, 1997;Sharma et al, 2000;Schützendübel et al, 2001;Lin and Aarts, 2012). Moreover, Cd also induces oxidative stress, which in turn mediates cellular damage in various plants and animals (Shim et al, 2009;Gallego et al, 2012).…”

Interaction and accumulation of manganese and cadmium in the manganese accumulator Lupinus albus

“…Visible symptoms of Cd injury in plants often include leaf chlorosis and necrosis, the discoloration of leaf blades, browning of the root tips, and finally death (Sanità di Toppi and Gabbrielli, 1999). Root browning is reported to be due to the enhanced suberization or lignification of the root tips, and a consequent loss in nutrient uptake capacity (Schützendübel et al, 2001). In this study, the supply of Cd to Mn-starved plants had negative effects on plant growth, accompanied by strong reductions in leaf chlorophylls, with the roots turning a brownish colour.…”

“…Increases in MDA caused by Cd exposure have been widely observed (Sandalio et al, 2001;Schützendübel et al, 2001). In the present work, supplying Cd led to increased MDA root concentrations in both Mn-supply treatments, but only in the shoots of plants grown without Mn (Figure 2).…”