Effects of Different Soil Nickel Contents on Growth, Photosynthesis, Antioxidant Responses, and 2-Acetyl-1-Pyrroline Content in Fragrant Rice Seedlings

In order to investigate the effects of different soil Ni contents on the performances of fragrant rice seedlings, the present study conducted a pot experiment and adopted five soil Ni content treatments, i.e., 0 (CK), 50 (Ni50), 100 (Ni100), 200 (Ni200), and 400 (Ni400) mg kg(-1). The fragrant rice seedlings were planted in these soils with different Ni contents. The results showed that there was no significant difference between CK and Ni50 treatment in growth parameters and biochemical indexes of seedlings. Compared with CK, Ni100, Ni200, and Ni400 treatments significantly decreased plant height, stem diameter, fresh weight, dry weight, and relative water content of seedlings. Lower net photosynthetic rates were recorded in Ni100, Ni200, and Ni400 treatment than CK. Compared with CK, Ni100, Ni200, and Ni400 treatments significantly reduced chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll contents. The activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) significantly reduced in Ni400 treatment compared with CK. Moreover, compared with CK, Ni200 and Ni400 treatment significantly increased H2O2, malondialdehyde (MDA), ascorbic acid (ASA) and glutathione (GSH), proline, and soluble sugar contents. Compared with CK, Ni200 and Ni400 treatments also enhanced nitrate reductase (NR) activity. In addition, Ni200 and Ni400 treatments significantly decreased the 2-acetyl-1-pyrroline (2-AP) content in fragrant rice seedlings. Our study would provide new information for the Ni-remediation of paddy soils and reducing Ni-induced effects on rice production.