INVOLVEMENT OF CATECHOLIC COMPOUNDS IN MORPHOGENESIS OF IN-VITRO POTATO PLANTS EFFECT OF METHYLGLYOXAL-BIS(GUANYLHYDRAZONE)

The occurrence and amount of catecholic compounds in potato vitroplant s (Solanum tuberosum L. cv. Bintje) during growth were investigated. B iogenic amines such as 3,4-dihydroxyphenylalanine (DOPA), dopamine and 2 other catecholic compounds, namely caffeic acid and protocatechuic aldehyde, have been identified and quantified with high sensitivity by high performance liquid chromatography with electrochemical detection , following selective extraction. These molecules are present in all p arts of-the plants and their content (DOPA, dopamine, caffeic acid) in creases parallel to growth; caffeic acid is mainly concentrated in tub ers while leaves are the richest organs in dopamine. Addition of exoge nous dopamine to the culture medium caused a great stimulation of grow th, especially of aerial parts. When methylglyoxal-bis(guanylhydrazone ) (MGBG), an inhibitor of spermidine biosynthesis, was added to the cu lture medium, it produced morphogenetic effects that are correlated to changes in dopamine amount. This inhibitor decreased the dopamine con tent of-aerial parts when it inhibited their growth and enhanced this catecholic compound in tubers when it stimulated their development; MG BG also produced a large increase in caffeic acid, probably linked to the stimulation of conjugated polyamines previously shown in tubers. T hese results support the hypothesis that catecholic compounds are invo lved in the morphogenesis of potato plants.