Uptake of tritiated 1,2-dibromoethane by Tradescantia floral tissues: relation to induced mutation frequency in stamen hair cells

Inflorescences of two clones of Tradescantia (02 and 4430) have been exposed to the gaseous form of tritium-labeled 1,2-dibromoethane (DBE). A comparison of chemical exposure concentration and tissue dose for various exposure periods indicated that DBE readily and rapidly penetrated through the outer sepal and petal tissues to the critical stamen hair cells - the targets for mutation induction. Bud and open flower tissues of both clones contained generally similar amounts of [3H]-DBE after similar exposures; thus, a differential penetration or uptake of the mutagen into the tissues of these clones cannot account for the 7 to 9 fold difference between clones in pink mutation frequency elicited by DBE exposure. Autoradiographs of stamen hair cells showed clearly that the DBE was not localized, but distributed randomly throughout the cytoplasm and nucleus. Comparison of [3H]-DBE-induced pink mutation-response curves to those derived previously with unlabeled DBE revealed that the rad dose of tritium could not account entirely for the elevated mutation response following exposure to the [3H]-DBE. Plots of the total exposure to [3H]-DBE vs both tissue molar concentration of [3H]-DBE and pink mutation incidence following exposure to DBE made possible the construction of true target-tissue dose-response curves. (author)