Flower induction in Norflurazon-treated Pharbitis nil: photo-induction of photoperiodic sensitivity in seedlings grown in vitro and daylength sensitivity in partly bleached potted plants

Photo-induction of photoperiodic sensitivity in seedlings of the shortday plant Pharbitis nil Choisy was unaffected by Norflurazon when grown under sterile conditions on a medium containing sucrose. Photoperiodic sensitivity was induced by 6 h light or by intermittent illumination. This is discussed in relation to results reported elsewhere on photo-induction of the capacity for dark reversion of the far-red absorbing form of phytochrome. Application of Norflurazon to the tips of potted plants grown in the light caused bleaching of the youngest leaves and internodes and stimulated flowering at a day length of 11 h, which normally results in weak photoperiodic induction.