Phosphine-induced physiological and biochemical responses in rice seedlings.

Paddy fields have been demonstrated to be one of the major resources of atmospheric phosphine and may have both positive and negative effects on rice plants. To elucidate the physiological and biochemical responses of rice plants to phosphine, rice seedlings (30 d old) were selected as a model plant and were treated with different concentrations of phosphine (0, 1.4, 4.2, and 7.0 mg m(-3)). Antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and lipid peroxidation measured via malondialdehyde (MDA) were determined as indicators of the physiological and biochemical responses of the rice seedlings to phosphine exposure. Increasing concentrations of phosphine treatment enhanced the activity of SOD, POD, and CAT. In addition, the MDA content increased with increasing concentrations of phosphine. These results suggested that antioxidant enzymes played important roles in protecting rice seedlings from ROS damage. Moreover, rice seedlings were able to cope with the oxidative stress induced by low concentrations of phosphine via an increase in antioxidant enzymatic activities. However, oxidative stress may not fully be prevented when the plants were exposed to higher concentrations of phosphine.