Extrafloral nectaries are present on the first leaves appearing when the buds open. Located at the base of the petiole, they are stalked and have an apical pore. They are initiated early on the margins of leaf primordia. These organs are interpreted as reduced stipules consisting of one axis with its vascular system with the extremity occupied by a nectary. A viscous and clear nectar is extruded from the pore. Without vascularization, there is never an apical gland. Stalked nectaries are also observed on the adaxial surface of the lamina. Described as teratological events, they correspond to the deviation of a vein perpendicular to the plane of the leaf. For aerial organs these nectaries show clearly the close connection between the vascular system and the glandular extremity. The tissue structure of these stalked nectaries is similar to that of the marginal nectaries. The morphological and physiological signification of these structures is discussed.
展开▼
