Abstract:The zearalenone (ZEN) levels and cell uhrastructure in the shoot apex of winter wheat ( Triticum aestivum L. cv. Yanda 1817) during vernalization were studied by immunosorbent assays and electron microscopy. The main results showed that the ZEN content in seed embryo increased during vernalization, and reached the maximum at week 4, and decreased thereafter. The obvious uhrastmctural changes of apex appeared after 4 weeks of low temperature. The apex cells enriched organelles, such as plastids, mitochondria, rough endoplasmic reticula. A lot of plastids and mito- chondria were irregular being budding or dumbbell shaped. The invagination of the plasma mem- brane and the nuclear substance transpassing though cell wall were visualized. Application of malathion (MAL), an inhibitor of ZEN biosyntheses, inhibited the formation of ZEN during vernalization; also affected the ultrastructure of apex cells of the induced seedling. The application of exogenous ZEN might promote the development of plastid, mitochondrion, rough endoplasmic reticulum and dictyosome.