Investigation of the effect of Cadmium pollution and irrigation with magnetized water on the growth and antioxidants of vetiver grass

Heavy metals (such as Cadmium, Cd) are one of the main pollutants in the environment, and their toxicities has caused concern due to their adverse effects on public health. Cd is a mineral pollutant for soil and a toxic element for plants and has negative effects on plant growth and yield which anthropogenic activities including farming, manufacturing, transporting etc. cause Cd accumulation in the environment. In order to control the entry of these pollutants into the food chains and also to improve the growth and yield of plants under pollution conditions, different management methods are used. One of the new methods is using of magnetized water in order to increase the plant's resistance to the pollution condition and also to control the uptake of this pollutant into plant tissues. Previous studies have solely reported on the phytoextraction and Phyto stabilization effects of heavy metals uptake in Vetiver grass. Also, magnetized water has been studied by researchers however, to date, there has been little studies about the effects of magnetized water on efficiency of phytoremediation and biochemical responses of plants. Therefore, the objective of this study was to investigate the effects of magnetized water on biochemical responses of vetiver plant and its phytoremediation efficiency under Cd pollution conditions.

In order to study the effect of magnetic field on Cadmium (Cd) removal by vetiver grass (Vetiver Zizanioides), a study was conducted in the central nursery of Green Area and Parks Organization Bandar Abbas Municipality, Bandar Abbas, Iran, from March 20, 2020 to February 18, 2021. This pot experiment was conducted as a factorial arrangement based on a completely randomized design with three replications. The studied soil was sampled (surface layer, 0-30 cm) from an agricultural soil where located in Baghu village, Bandar Abbas, Iran, and after air-drying, it was sieved (2 mm) to measure some important physical and chemical properties. The studied factors were Cd in 4 levels (0, 0.5, 1, and 2 mg L-1) and irrigation water in 3 levels (magnetized water, semi-magnetized water, and non-magnetized water). At the end of the experiment, the concentration of Cd in root and shoot of vetiver grass, translocation and bioaccumulation factors and some growth and antioxidants of the plant including activity of Superoxide Dismutase (SOD), Catalase (CAT), and Peroxidase (POD), phenol, flavonoid and anthocyanin was measured. Some phytoremediation indexes including translocation factor (TF), bioaccumulation factor (BF), and uptake index of Pb in root and shoot (UI) were calculated were measured. Finally, in order to statistical analysis of the data, SAS 9.1 software was used, and in order to compare the means, Duncan's multiple-range test (DMRT) (P<0.05) was used and graphs were drawn using Excel software.

The results of variance analysis showed that the use of different levels of magnetized water and Cd pollution significantly affected the accumulation of Cd in roots and shoots, the bioaccumulation index (BF) and the translocation factor (TF) of Cd from the roots to the shoots. Also, the interaction effects of irrigation water and Cd concentration on them was significant (P<0.05). Biomass production, activity of antioxidant enzymes and non-enzymatic antioxidants of vetiver plant were significantly affected by the applied treatments, as well. The interaction effect of the studied treatments was also significant except for the activity of superoxide dismutase (SOD), anthocyanin and plant dry weight (P<0.05). Based on the results of means comparison, the highest concentration of Cd in roots and shoots, T), and BF were allocated to the magnetized water treatment, and by changing the concentration of Cd, the effect of magnetized water on plant responses changed, as well. The activity of enzymatic and non-enzymatic antioxidants also increased with increasing the concentration of Cd, but the treatment of magnetized water was a superior treatment. In general, the results obtained from this study showed that the use of magnetized water can be useful for increasing the resistance of plants to the stress of Cd pollution. Vetiver plant, in the conditions of facing with increasing the concentration of Cd pollution, initiates growth and antioxidant responses, which antioxidant responses are actually a defense mechanism of plants to deal with adverse environmental effects. On the other hand, the use of magnetized water technique in irrigating plants under Cd pollution conditions can have a significant effect on the type of plant responses and help the plant to withstand environmental stress (here Cd pollution). The use of magnetized water had a significant effect on the bioaccumulation index and the transfer factor of cadmium from the roots to the shoots. Nevertheless, to confirm the results obtained from this research, it is suggested to conduct more studies on higher levels of pollution, other heavy metals and different plants.