POLYAMINE IMPLICATION IN POTATO TUBERIZAT ION (SOLANUM-TUBEROSUM CV BINTJE)

When potato plants are grown in vitro with 0.5 mM methylglyoxalbis (gu anylhydrazone), MGBG, inhibitor of spermidine biosynthesis, we can see a stimulation of tuberisation associated with a decrease in the free polyamine content of the leaves and with an increase of the conjugated polyamine content of the tubers. The analysis of C-14-putrescine tran sport, fed to a leaf, shows on the one part a bidirectional transport of this compound towards growing organs (buds, tubers) and, on the oth er part, a reinforcement of the sink strength of the tuber by MGBG. Th is increase in the radioactivity of the tubers is due to a doubling of the labelling of free polyamines and of that of the aqueous phase tha t contains the conjugated polyamines. The results are discussed in rel ation with a possible role of polyamines in the tuberisation process.