Two commonly used herbicides, Pendimethaline and Oxyfluorfen, were evaluated for their cytotoxicity in cv. Suwan. Seed soak treatments were given for 6 hr and 12 hr with aqueous solutions of these herbicides with concentrations 5, 25 and 50 ppm. Seeds were then thoroughly washed, and planted in the field. Germination percentage was recorded. Young emerging tassels were fixed at flowering stage in aceto-alcohol fixative for 48 hr and then standard aceto-carmine squash preparations of anthers were prepared to score the frequency of dividing cells and various abnormalities (Table 1).
Marked inhibition of germination was observed in the case of both herbicide treatments. Dose-dependent inhibition of meiosis as indicated by decline in meiotic index was observed. Pendimethaline was more injurious to cell division in terms of frequency of dividing cells (95.8% - 87.1%) and abnormalities (4.2% - 12.9%) than Oxyfluorfen, which showed a higher meiotic index (97.5% - 93.2%) and less abnormality (2.5% - 6.7%). Pollen sterility also was much higher in the case of Pendimethaline treatment (1.29% - 7.32%) than Oxyfluorfen (0.57% - 3.16%). Pendimethaline treatment induced stickiness, multivalents and unequal separation of chromosomes, while Oxyfluorfen induced only laggards and stickiness.
Table 1. Cytotoxic effects (in percent) of herbicides in pollen mother
cells.
| Herbicide | Conc. ppm. | Tmt. (h) | Germination | Meiotic index | Abnormal PMCs | Pollen sterility | Meiosis I | Meiosis II | Meta-I | Meta-II |
| Control | 0 | - | 97.0 | 99.6 | 0.4 | 0.54 | 56.8 | 42.8 | 14.5 | 15.3 |
| Oxyfluorfen | 5 | 6 | 95.0 | 97.5 | 2.5 | 0.57 | 67.0 | 30.5 | 22.5 | 18.0 |
| 12 | 80.0 | 97.0 | 3.0 | 2.20 | 69.8 | 27.2 | 28.6 | 14.9 | ||
| 25 | 6 | 90.0 | 96.5 | 3.5 | 1.63 | 63.5 | 33.0 | 27.5 | 22.9 | |
| 12 | 65.0 | 94.9 | 5.1 | 2.5 | 61.7 | 33.2 | 29.0 | 20.3 | ||
| 50 | 6 | 54.5 | 95.3 | 4.7 | 2.10 | 65.3 | 30.0 | 28.8 | 12.9 | |
| 12 | 36.4 | 93.2 | 6.7 | 3.16 | 84.7 | 8.5 | 48.5 | 1.2 | ||
| Pendimethaline | 5 | 6 | 95.2 | 95.8 | 4.2 | 1.29 | 68.5 | 27.3 | 31.5 | 15.5 |
| 12 | 80.9 | 93.9 | 6.3 | 1.47 | 67.0 | 26.7 | 25.8 | 13.7 | ||
| 25 | 6 | 85.0 | 91.7 | 8.3 | 2.19 | 66.8 | 24.9 | 35.0 | 15.5 | |
| 12 | 56.5 | 91.3 | 8.7 | 5.42 | 65.0 | 26.3 | 32.1 | 15.6 | ||
| 50 | 6 | 51.0 | 90.3 | 9.7 | 6.12 | 64.0 | 26.3 | 32.8 | 17.2 | |
| 12 | 35.0 | 87.1 | 12.9 | 7.32 | 62.5 | 24.7 | 26.0 | 15.7 |
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