Development, structure and senescence of colleters in Gardenia lucida Roxb. (Rubiaceae)

Colleters are found on the adaxial basal part of the stipule and calyx of Gardenia lucida. They secrete a yellow transparent resinous substance commonly known as "Dikamali gum". They develop on both the stipule and calyx from a group of epidermal and hypodermal initials. A mature colleter consists of a central core of elongated parenchymatous cells surrounded by a palisade-like secretory epidermis. Druses type crystals of calcium oxalate are frequent in the colleters. At the time of senescence the central cells show lignification and the presence of tannin.