Carbonized Apple Branches Decrease the Accumulation and Damage of Cadmium on Apple Rootstock by Reducing DTPA-Cd in Soil

Abstract

To explore the effects of carbonized apple branches on cadmium(Cd) accumulation and its damage to apple rootstock, the rootstocks of apple(Malus hupehensis Rehd.) in pots containing soil together with 0.5% and 1%(ω) carbonized apple branches were irrigated by a nutrient solution containing CdSO4. The content of DTPA-Cd(cadmium extracted by diethylenetriamine pentaacetic acid) in the potting soil, and the accumulation of Cd in the roots, stems, and leaves of apple rootstocks, were subsequently monitored. The activities of antioxidant enzymes in roots and leaves, root cell death, and the net photosynthesis rate were further analyzed. The results showed that the concentration of DTPA-Cd in the potting soil with carbonized apple branches was significantly lower than that without carbonized apple branches(Cd-only). Compared with the Cd-only treatment, the concentration of DTPA-Cd in the potting soil decreased by 17.50% and 25.55% in the treatment with 0.5% and 1%(ω) carbonized apple branches for 12 days. The Cd accumulation in roots, stems, and leaves; the accumulations of superoxide anions(·O2-), hydrogen peroxide(H2O2), and malondialdehyde(MDA) in roots and leaves; and the amount of cell death in the roots of apple rootstock treated by carbonized apple branches were significantly lower compared to the Cd-only treatment. However, the activities of superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) in the roots and leaves, and the net photosynthesis rate of apple rootstock treated by carbonized apple branches, were significantly higher than under the Cd-only treatment. Compared with the Cd-only treatment, Cd accumulation in roots decreased by 29.49% and 37.18% in the treatment with 0.5% and 1%(ω) carbonized apple branches for 12 days, and the amount of cell death decreased by 22.73% and 29.09%, respectively. Our results show that carbonized apple branches reduce the uptake and accumulation of Cd in apple rootstock by reducing the content of DTPA-Cd in the soil, thereby alleviating the damaging effect of Cd on cells and photosynthesis. Moreover, the use of 1%(ω) carbonized apple branches was more effective than 0.5%(ω).