5-Fluorodeoxyuridine inhibition of photoperiodically induced flowering inChenopodium rubrum L.

Flowering in the short day plant Chenopodium rubrum was inhibited by 5-fluoro-deoxyuridine (FDU) at a concentration of 4×10 −6 M and higher when applied during photoperiodic induction or immediately afterwards. This inhibition is always accompanied by a general reduction of growth ( e.g. a decrease in the first leaf length). The mitotic activity within the shoot apex is completely blocked by FDU application during the photoperiodic treatment. The floral induction (evocation sensu Evans) was not cancelled in this situation as was revealed when reversing the FDU effect by thymidine application. One day after the end of the photoperiodic treatment (the plants were transferred to continuous light again) the FDU inhibition becomes irreparable. The results indicate that DNA synthesis and hence the mitotic activity are not obligatory prerequisites for photoperiodic floral induction in Chenopodium . Low concentrations of FDU may promote flowering under suboptimal floral induction.