2,4-Dichlorophenoxy acetic acid and indoleacetic acid partially counteract inhibition of organogenesis by difluoromethylornithine

Difluoromethylornithine (DFMO) is a well known inhibitor of putrescine biosynthesis that has been reported to interact in varying ways with auxins such as indoleacetic acid (IAA) and 2,4-dichlorophenoxy acetic acid (2,4-D). In the present report DFMO is shown to inhibit root formation in isolated hypocotyl segments of Euphorbia esula L. (leafy spurge) grown in the dark on solidified nutrient media in Petri dishes. Shoot formation was only slightly inhibited by DFMO and only on media with salts and vitamins diluted 10-fold. 2,4-D inhibited both root and shoot formation in full strength or diluted media. Simultaneous application of both compounds resulted in partial reversal of root inhibition, but only at 450 n M 2,4-D, the highest concentration used. In both media IAA also partially reversed DFMO effects on root formation. The effects of DFMO, 2,4-D or IAA on root (or shoot) formation do not appear to be closely related to endogenous content of the polyamines determined by high performance liquid chromatography.