Effect of agro-industrial waste amendment on Cd uptake in Amaranthus caudatus grown under contaminated soil: An oxidative biomarker response
In the present study phytoavailability of Cd, growth yield, cellular Cd accumulation and oxidative stress responses were studied in leafy vegetable Amaranthus caudatus under soil amendments. The test plant was cultivated in Cd contaminated soil (6 µgCdg(-1) soil) amended with different doses: 0.5, 2, 5 and 10 percent of rice husk (RH), saw dust (SD), farmyard manure (FYM), farmyard in combination with nitrogen, and phosphorus and potassium (FYM+NPK). Phytoavailability of Cd in amended soil and cellular Cd accumulation in edible parts (shoot) of A. caudatus declined maximally with 5 percent dose of each amendment, and decrease in Cd content in tissues was 36, 45, 23 and 14 percent under FYM, FYM+NPK, RH and SD amendments, respectively, over the value recorded in plants grown in Cd contaminated non-amended soil (Cd(+)NA soil). The shoot yield in control plant cultivated in the absence of Cd without amendment (Cd(-)NA soil) was 18.1 ± 0.98 gfwplant(-1) and it was declined up to 50 percent (9.2 ± 0.80 gfwplant(-1)) when plants were grown in Cd(+)NA soil. Amendments with 5 percent doses of FYM+NPK and FYM enhanced the yield up to 26.5 ± 0.57 and 20.5 ± 1.00 gfwplant(-1), respectively, which may be correlated with better mineral nutrients and organic carbon content in amended soil. RH and SD amendments with similar doses improved in yield up to 16.9 ± 0.43 and 15.2 ± 0.45 gfwplant(-1), respectively, however, it was still less than that of control. Further, correlation analysis of growth yield, Cd concentration and oxidative stress under these conditions suggest that with the decrease in cellular Cd concentration following amendment the level of oxidative markers (oxidants: O2(-) and H2O2 and lipid peroxidation: malondialdehyde; MDA) declined as a result of significant enhancement in the activity of enzymatic antioxidants (peroxidase, ascorbate peroxidase, superoxide dismutase, dyhydroascorbe reductase and catalase). Thus, the present technique can efficiently reduce the metal load in food chain and also increase plant yield, hence it could be applied in catchments area of urban cities where metal contamination has become an unavoidable factor.