The Mode of Flower-Inhibiting Action of Ethylene in <italic>Pharbitis nil</italic>

Abstract

The inhibitory effect of ethylene on photoperiodic flower induction in Pharbitis nil was investigated in relation to the time of ethylene application. Ethylene applied during an 18-h dark period not only made the dark period non-inductive, but also greatly inhibited the flower-inducing effect of the 2nd 18-h dark period given 6 h after the end of the first dark period. The second dark period was inductive when it was given 30 h after the end of the first dark period, during which ethylene was applied. Ethylene applied during the light period prior to an inductive dark period had no inhibitory effect, suggesting that ethylene given during the dark period produces some flower-inhibiting entity.