The Possible Role of Auxin in Reversing Photoperiodic Induction of Flowering in a Short-day Plant, Chenopodium rubrum L.

Abstract

IAA (3.10 -4 M) inhibited the photoperiodic induction of flowering in the short day plant Chenopodium rubrum L. when applied during the inductive period to the shoot apex. When applied instead to the cotyledons it is much less effective, but only if the transport of auxin to the apex is inhibited by internode elongation due to gibberellic acid application. In some cases, as with TIBA treatment, this transport was reduced to less than 1 %. The rate of auxin transport was estimated using analytical methods or by semiconductography. The step-wise application of IAA during three or four inductive short days revealed that the inhibitory effect is restricted to the later stage of induction not inhibitable by actinomycine D or cycloheximide. The possible role of auxin in evocation is discussed.