Cadmium Toxicity In Seedlings Research Articles

Exogenous ascorbic acid application alleviates cadmium toxicity in seedlings of two wheat (Triticum aestivum L.) varieties by reducing cadmium uptake and enhancing antioxidative capacity.

The aggravation of soil cadmium (Cd) pollution is a serious threat to human food health and safety. To reduce Cd uptake and alleviate Cd toxicity in staple food of wheat, a completely random experiment was performed to investigate the effect of exogenous ascorbic acid (AsA) on Cd toxicity in two wheat varieties (L979 and H27). In this study, the treatments with combinations of Cd (0, 5, and 10µmol L-1) and AsA (0, 50, and 200µmol L-1) were applied in a hydroponic system. Toxicity induced by Cd inhibited biomass accumulation; decreased wheat growth, photosynthesis, and chlorophyll content; increased lipid peroxidation; and reduced activity of superoxide dismutase (SOD), but stimulated catalase (CAT) and peroxidase (POD). The addition of AsA significantly improved the growth status by increasing the wheat biomass, chlorophyll content, photosynthetic rate, protein concentrations, and antioxidant enzyme activity. Besides, AsA significantly decreased Cd concentration of shoot and root by 14.1-53.9% and 20.8-59.5% in L979 and 23.7-58.8% and 22.1-58.1% in H27 under Cd5, and 23.7-53.6% and 16.6-57.1% in L979 and 21.5-51.6% and 15.3-54.0% in H27 under Cd10, respectively. Malondialdehyde (MDA) accumulation was decreased remarkably with the addition of AsA by 31.2-32.9% in L979 and 27.1-45.2% in H27 under Cd10, respectively. Overall, exogenous application of AsA alleviated the Cd toxicity in wheat plants by improving the wheat growth, soluble protein content, photosynthesis, and antioxidant defense systems, and decreasing MDA accumulation.

Heat exposure alters the expression of SOD, POD, APX and CAT isozymes and mitigates low cadmium toxicity in seedlings of sensitive and tolerant rice cultivars

A 0-500 μM Cd(2+) alone and/or heat stress in rice cv. DR-92 (sensitive) and cv. Bh-1 (tolerant), altered the banding patterns of SOD, CAT, POD and APX enzymes in roots/shoots. In controls, six/seven activity bands for POD in roots/shoots were observed. The band intensities of some decreased under combination of Cd(2+) + heat stress. Six SOD isoforms in shoots of cv. Bh-1 and three in cv. DR-92 appeared. In sensitive cv. DR-92 a trinuclear Cu/Zn/Mn-SOD 1 isozyme was upregulated in shoots under Cd/HS/Cd + HS treatments whereas a suppression in the same was noticed in roots. Under Cd alone the Cu/Zn/Mn-SOD 2 was strongly induced in roots which was otherwise absent in all HS treatments. POD R7 band was absent in HS alone but was induced under Cd(2+) + HS treatments in rice cv. DR-92. In tolerant cv. Bh-1, isozyme Mn-SOD 3 was induced under Cd alone but was absent under HS. Cu/Zn/Mn-SOD 2 and Cu/Zn/Mn-SOD 3 were strongly induced in roots and shoots under low or moderate Cd(2+) + HS treatments. APX R4/CATR2 isozymes which were absent under Cd(2+) alone or HS alone were induced under combination of Cd(2+) + HS indicating de novo synthesis of enzyme proteins under combined stressors. Decreased band intensities under Cd(2+) + HS suggest a cross-talk between response pathways of Cd(2+) and heat stress in rice. Results suggest Cd(2+) specific, heat-specific, tissue specific and differential expression of SOD/POD/APX/CAT and that Mn-SOD 3/APXR4/CATR2 seem to form important components of antioxidant defense in rice roots under combination of Cd(2+) + HS which helps to mitigate the effect of low Cd(2+) toxicity in tolerant rice cv. Bh-1.