Abstract
Shoot extension during a growth season has been investigated in three morphological types of floriferous annual shoots (monocyclic with or without a small axis with immediate development and bicyclic) on four types of parental branches within 4-year-old Juglans regia L. 'Lara' growing in the south-west of France. The morphological type of parental branches has an influence on the time of inception of monocyclic shoot extension. No correlation has been found between the parental shoot length and monocyclic shoot length, while a positive correlation has been found between parental shoot length and bicyclic shoot length. Bicyclic annual shoots expand during two successive flushes : in spring and summer, respectively. The intra-annual resting phase results in the presence of a series of cataphylls in the median part of the shoots. Spring shoots and summer shoots may be distinguished by variations in form and in number of foliar organs. Annual shoots exhibiting an acrotonic axis with immediate development or a summer shoot generally possess greater extension periods and lengths of spring shoots than the unbranched ones.Key words: Juglans regia 'Lara', persian walnut, shoot extension, primary growth, morphology, annual shoot.