POLYAMINE IMPLICATION DURING SOYBEAN FLOWERING INDUCTION AND EARLY REPRODUCTIVE TRANSITION OF VEGETATIVE BUDS

Soybean (Glycine max (L.) merr. cv. Williams, M.G. III) plants exposed to non-inductive long days (LD: 9 h. light and a 3 h. light break in the middle of the dark period) as well as to inductive short days (SD: 9 h. light and 15 h. darkness) were used to analyse the involvement o f polyamines (PAs) during the first 9 days of the photoperiodic induct ion of flowering. During this period, PA varied in a different way. Fr ee (S), acid soluble-bound (SH) and acid insoluble-bound (PH) putresci ne (Put), spermidine (Spd), spermine (Spm) and cadaverine (Cad) were f ound in the stem terminal bud. PH-Put and PH-Cad tits decreased only a fter the Ist SD. After the 3rd SD there was a transient decrease of SH -Put and an increase in S-Put. From 3rd SD to 9th SD PH-Cad decreased while SH and S-Cad increased, and PH-Put and S-Spm decreased. These re sults demonstrate that PA are implicated in a different way each step of the photoperiodic flower induction and the meristematic transition from the vegetative to the reproductive stage of an entire soybean pla nt.