STUDIES OF PHLORIDZIN IN MALUS

Abstract

The phloridzin content of dormant terminal twigs of Malus rootstock clones was not related to the vigor imparted to the scions. In young seedling trees it varied with the nutritional status of the plant; an acute deficiency of nitrogen, sulphur, or calcium resulted in a significant increase in phloridzin accumulation. Phloridzin is synthesized readily in the leaf from C¹⁴O₂ in the light and appears to be stable once formed. Phenylalanine-C¹⁴ and tyrosine-C¹⁴, when fed to leaf disks, are incorporated into the C₆–C₃ moiety of phloridzin which includes ring B. Tyrosine is not as effective as phenylalanine. Acetate-C¹⁴ is incorporated into ring A. Phloroglucinol is not involved in the synthesis of phloridzin. A method for the quantitative determination of phloridzin is described, also a semimicro method for its alkaline hydrolysis. The large amounts of radioactive D-glucitol formed from a wide variety of precursor compounds indicate a central role for it in the carbohydrate metabolism of Malus.