Physiological Response of Vetiveria zizanioides to Cadmium-prometryn Composite Pollution Stress

The response of vetiver grass (Vetiveria zizanioides) to single or co-presence of Cd and prometryn was investigated in hydroponic in the greenhouse. The fresh weight, chlorophyll content, root activity, and antioxidant enzyme system of V. zizanioides were analyzed. The results show that the total fresh weight and fresh weight growth rate of V. zizanioides in single Cd treatment showed no significant difference (P > 0.05) compared to the control (without Cd or prometryn). However, single prometryn and Cd-prometryn co-presence significantly decreased (P < 0.05) the total fresh weight and growth rate of V. zizanioides. Specifically, single prometryn treatment decreased the total fresh weight and growth rate of V. zizanioides by 32.72 g and 11.66%, respectively. Cd-prometryn co-presence decreased the total fresh weight and growth rate by 16.85 g and 6.69%, respectively. The contents of Chla, Chlb, and Chlt in V. zizanioides were decreased in single prometryn treatment, while increased under single Cd and Cd-prometryn co-presence treatments. V. zizanioides root activity was significantly higher in single Cd or prometryn, and Cd-prometryn co-presence treatments compared to control excepting at 0 d and 6 d. With the extension of cultivation time, the contents of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) in V. zizanioides roots, stems, and leaves showed different trends under Cd and prometryn single or composite stress. V. zizanioides showed strong tolerance to single/composite pollution stress of Cd and prometryn via adjusting the antioxidant enzyme system. The research results provide theoretical supports for screening artificial wetland plants for efficient remediation of single or composite pollution of heavy metal and pesticide.