Changes in the levels and composition of sterols in different tissues of <i>Lolium temulentum</i> plants during floral development

Abstract

Free, esterified and glycosylated sterols were analysed separately from the shoot apices, leaves, leaf sheaths and stems of Lolium temulentum L. (strain Ceres) plants during floral development. Short‐day grown plants (50 days old) were induced to flower by exposure to a single long day. The four major sterols found by GC‐MS analysis were sitosterol, cholesterol, campesterol and stigmasterol. The sterol levels in the shoot apex were much higher than those in the leaf, leaf sheath and stem. A much greater proportion of cholesterol was found in the shoot apex than in other tissues and this may reflect a specific association of cholesterol with meristematic and/or reproductive tissues. During the inductive treatment, the sterol levels decreased in all four tissues. The major effect during early differentiation was the occurrence of transient increases in the free and esterified sterol levels in the leaf and the stem tissues. The steryl ester content peaked 24 h before the appearance of double ridges, followed by a peak in free sterol content at the double ridge stage. Similar changes could not be detected in the shoot apices. This is the first report of the sterol composition of developing shoot apices, and the results emphasize the dynamic nature of sterol metabolism during reproductive growth of L. temulentum.