R B Subramanian
Articles written in Proceedings – Plant Sciences
Volume 99 Issue 5 October 1989 pp 423-429
In some Apocynaceae a group of 10–15 resin glands is present as finger-like projections on the adaxial side of the proximal end of the petioles and sepals or petals. They originate from a group of epidermal and sub-epidermal cells. At maturity the glands are differentiated into a short stalk and a clavate head. The latter is composed of epidermal secretory cells and sub-epidermal parenchyma. Structurally and ontogenetically the resin glands resemble extrafloral nectaries and the standard colleters of the Rubiaceae. However, histochemical tests for lipophilic substances revealed that these glands secrete resin. The pale yellow, viscous secretion is released by cuticular bursting and covers the tender shoot apices and developing buds. The position and the secretory activity of the resin glands in relation to their function is discussed.