The physiological responses of dimethyl sulfoxide (DMSO) exposure were investigated in rice (Oryza sativa L. cv. XZX 45) seedlings. The seedlings were hydroponically exposed to different concentrations of DMSO for 72 h. Results showed that a linear decrease in relative growth rate and water use efficiency was observed with rice seedlings with increasing DMSO concentrations. The estimation of cell death measured by Evans blue uptake also indicated DMSO-induced damage in root tissues. Negligible decrease in chlorophylls was noted, while significant reduction in carotenoids content was only observed at 13.54 mM DMSO. Although DMSO did not have any significant effect on protein content in roots, the protein content in shoots was significantly decreased in a dose-dependent manner. Proline content in both plant tissues was positively affected by DMSO exposure, responding an inverted U-shaped curve with DMSO concentrations. Results also showed that DMSO-induced accumulation of hydrogen peroxide (H 2 O 2 ) was evident in roots rather than shoots. DMSO did not result in any significant changes in superoxide dismutase and peroxidase activities as well as malondialdehyde content. Catalase (CAT) activity in both roots and shoots was quite sensitive to changes in DMSO treatments than other enzymes, suggesting that CAT may play central role in the detoxification of H 2 O 2 in rice seedlings under DMSO exposure. Results suggest that growth inhibition and cell death of rice seedlings caused by DMSO exposure were largely related to the accumulation of H 2 O 2 in plant tissues.

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