Effects of Chlorine Dioxide on Bleaching in Duckweed and on Germination and Early Seedling Growth of Barley and Indian Mustard

초록

This study evaluated the growth-inhibitory effects of chlorine dioxide (ClO2) on duckweed (Lemna spp.), barley (Hordeum vulgare), and indian mustard (Brassica juncea) under different concentrations (0-250 mg L-1) and exposure times. In duckweed, the relative green area gradually decreased as both ClO2 concentration and exposure time increased. The ET50 values at ClO2 concentrations of 50, 100, 150, 200, and 250 mg L-1 were 5.33, 2.46, 2.79, 2.62, and 2.53 h, respectively. In contrast, the EC50 values at exposure times of 3, 5, 7, and 9 h were 107.8, 58.3, 11.0, and 7.6 mg L-1, respectively, indicating a marked increase in growth inhibition with prolonged exposure. Seed germination of barley and indian mustard declined with increasing ClO2 concentration and soaking duration. However, even after soaking for 24 h at the highest concentration (250 mg L-1), germination rates remained relatively high at 80.0% in indian mustard and 75.4% in barley. In contrast, seedling fresh weight was substantially reduced after 24 h of soaking, reaching 60.0, 40.0, 27.5, 25.0, and 22.5% of the untreated control in indian mustard and 87.9, 86.6, 77.6, 72.0, and 71.1% in barley at 50, 100, 150, 200, and 250 mg L-1, respectively. Root length was the most sensitive indicator of ClO2 phytotoxicity in both species, decreasing to 30.2-47.6% of the control in indian mustard and 0.8-10.2% in barley after 24 h of treatment. These results demonstrate that the growth-inhibitory activity of ClO2 is strongly dependent on both concentration and exposure time and that ClO2 is more effective at suppressing post-germination seedling growth, particularly root elongation, than seed germination. Therefore, chlorine dioxide has considerable potential as an environmentally friendly management tool for early-stage weeds and aquatic plants.

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