Ethylene in the control of photoperiodic flower induction in Pharbitis nil Chois.

The content of endogenous ethylene in the seedlings of Pharbitis nil subjected to 16-hour long inductive night is low during the first half of a dark period, then it increases considerably in the second half of the night. Ethrel, the compound releasing ethylene, applied to the cotyledons of the seedlings, increases the amount of endogenous ethylene in them and at the same time inhibits the flowering, especially when ethrel was applied during the first half of an inductive night, when the content of endogenous ethylene in the seedlings is low. The auxin, inhibiting the flowering of Pharbitis, causes at the same time the increase in the production of endogenous ethylene. PCIB, an inhibitor of auxin action reverses the inhibiting influence of ethrel on flowering. On the other hand the combined application of ethrel and TIBA, the inhibitor of auxin polar transport, causes the increase of the flowering inhibition. CoCl2, the inhibitor of ethylene biosynthesis, and AgNO3, the inhibitor of ethylene action, reverse partly the inhibiting influence of auxin. It suggests that ethylene could take part in auxininhibition of flowering. The all obtained results seem to suggest the participation of ethylene in the control of the flower photoperiodic induction.