Figure 3. Dose-dependent reduction of horsetail mobility by X ray exposure.

(A) Irradiation with doses of up to 200 Gy leads to a linear reduction (r² = 0.937) of the number of mobile horsetail nuclei per sporulating culture. Beyond 200 Gy there was no further effect. Data points reflect the mean of 3 experiments (±SD). (B) X irradiation significantly reduces average horsetail speed at ≥50 Gy (p < 0.0001) relative to control, while there is only a slight insignificant further reduction up to 300 Gy, indicating that MT-driven horsetail mobility is radioresistant. Controls: The red circle indicates the horsetail speed of cells in sporulation medium without minerals and vitamins after irradiation with 100 Gy, to test for nutrient effects on speed measurements. The dark-green asterisk at the lower right (FA) indicates the mobility of the leading edge of the horsetail nuclei after 4% formaldehyde fixation. (C) Effect of the MT-poison TBZ on horsetail mobility. Treatment of sporulating culture with TBZ (20 and 40 μg/ml TBZ) lead to a highly significant (p < 0.001) reduction of horsetail speed. The images to the right display a control cell (Con; nuclear equator shown) and a cell treated with 40 μg/ml TBZ (40 μ TBZ) that exhibits the loss of long astral microtubules. Box blot, whiskers show minimum and maximum speed observed.