The Behaviour of Phloridzin in the Coleoptile Straight-growth Test

Phloridzin was identified as one of the two inhibitors of coleoptile-section extension in the acid fraction of extracts of apple shoots. The tips of the sections showed a characteristic flaccidity and staining at concentrations of 200 p.p.m. and above. Sections which had been inhibited by phloridzin did not recover so well after washing and transfer to sodium β-indolylacetate as did those which had been in contact with an inhibitor from plum shoots. Phloridzin was more effective as an inhibitor than its breakdown products phloretin, phloroglucinol, p-hydroxyhydrocinnamic acid, or p-hydroxybenzoic acid. The scanty knowledge of the role of phloridzin in plant metabolism is briefly discussed.