IDENTIFICATION OF THE ACTIVE COMPONENT IN THE PAPILLA-REGULATING EXTRACT FROM BARLEY LEAVES

A partially purified extract from barley seedlings, referred to as the papilla-regulating extract (PRE), has been reported to induce both th e formation of oversize papillae and resistance to penetration by the powdery mildew fungus in inoculated, susceptible barley coleoptiles. P urification and identification of the active component in the PRE were accomplished in this study. Biological activity was monitored by bioa ssay. The extract, obtained from barley seedlings through autoclaving, was first passed through a C18 reverse phase column. The eluent, in w hich activity was detected, was next passed through a gel permeation c hromatography column packed with Sephadex LH-20 in 50% methanol. The a ctive fractions were chromatographed on a Bio-Gel P-2 column in water. Although xylonate was a major organic component in the active fractio ns from the P-2 column, authentic xylonate was not biologically active by itself After rechromatography in the P-2 column, it was determined by ion chromatography and inductively coupled argon plasma atomic emi ssion spectroscopy that the active compound was potassium phosphate. B ioassays using authentic potassium phosphates confirmed this conclusio n. The effects of the PRE were also found to be Ca2+-mediated. Potassi um phosphates in plants may be important in regulating papilla formati on and induced resistance.