Coronatine (1), produced by Pseudomonas coronafacience var. atropurpúrea, is a toxin which induces chlorosis on the leaves of Italian ryegrass; it also expands potato cells at concentrations of 1 X 10-7 mol/1.1 In this communication, we forward structure 1 for coronatine on the basis of spectroscopic data of the derivatives and x-ray crystallographic analysis of coronafacic acid (2b). 151-153 °C was formulated as C18H25O4N {m/e M+ found, 319.1753; caled, 319.1731) and shows the following spectral data, UV XmaxEtOH 208 nm (e 8378); IR iwKBr 1740 (fivemembered ring C=0), 1620 (C=C), 3270,1645,1525 cm-1 (-CONH-); NMR (90 MHz) ¿Me4SiCD3COCD3 0.94 (6 H, t, J = 7 Hz, CH2C//3), 3.15 (1 H, br. q, -CHCO), 6.50 (1 H, s, =CH). The high resolution mass spectrum of 1 indicates

Several workers have postulated the existence of a specific tuber-inducing stimulus in potato leaves. Grafting experiments brought forward evidence for the existence of the substance,1'2) which was formed in the leaves under proper conditions and translocated to the stolon tip. Recently, we have confirmed the occurrence of a tuber-inducing stimulus in

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Oxalic acid, isolated from leaf sheath extract of rice, has been identified as a potent sucking inhibitor against the brown planthopper. Potassium and sodium oxalate at concentrations of 0.1%–0.2% completely inhibited sucking on a 15% sucrose solution. Of twelve aliphatic acids commonly present in plants, only oxalic, maleic, and trans‐aconitic acids at 0.1%, significantly reduced sucking activity while Krebs cycle acids, such as citric, malic, and succinic, did not have any inhibitory effect. RÉSUMÉ L'ACIDE OXALIQUE COMME INHIBITEUR DE LA SUCCION DE NIPALARVATA LUGENS STÀL, (HOMOPTERE, DELPHACIDAE) L'acide oxalique, isolé des gaines foliaires du riz, a été identifié comme un puissant inhibiteur de la succion de Nilaparvata lugens. Les oxalates de potassium et de sodium aux concentrations de 0,1% et 0,2% inhibent complètement la succion d'une solution de sucrose à 15%. Parmi les douze acides aliphatiques généralement présents dans la plante, seuls les acides oxalique, maleique et trans‐aconique réduisent significativement à 0,1% l'activité de succion, tandis que les acides cycliques comme les acides citrique, malique et succinique n'ont pas d'effet inhibiteur.