POLYAMINES AND MORPHOGENESIS - EFFECTS OF METHYLGLYOXAL-BIS(GUANYLHYDRAZONE)

The effects of methylglyoxal-bis(guanylhydrazone) (MGBG), an inhibitor of polyamine biosynthesis were studied on tuberization and cellular p olyamine content using in vitro Solanum tuberosum (cv Binjte) plants. When MGBG was added to the culture medium, it produced a partial inhib ition of the growth of stems and leaves; it totally blocked rhizogenes is and strongly stimulated tuber formation. Morphogenetic effects of M GBG were correlated to a 40% decrease in free putrescine, spermidine, spermine content of the leaves and to a 28% decrease in spermidine tit er of the stems. In the tubers, this inhibitor did not change the free polyamine titer but increased by up to 85% the titer of conjugated pu trescine, spermidine, spermine. When the plants were grown in the dark , MGBG produced, like benzyladenine, a stimulation of the rate of tube rization and enhanced the content of conjugated polyamines in the tube r.These results support the hypothesis that polyamines play an importa nt role in the morphogenesis of potato plants. The role of polyamine c onjugation in tuber development is discussed.