Leaf colleters in Clusia burchellii Engl.: Structural and ultrastructural features of a little-known gland in Clusiaceae.

Clusiaceae species are known globally for the economic importance of their secretory structures; however, reports of colleters in the family are scarce. In the present study, we characterised the leaf colleters in Clusia burchellii by investigating the morphology and anatomy of the glands, the histolocation of the major chemical substances present in the secretory cells and the cellular aspects associated with the synthesis and release of the secretion. Leaf samples at different developmental stages were collected and examined under light and electron microscopy. Histochemical tests were performed. Colleters of the standard type occur at the base of the petiole, are sessile or short pedunculated, and originate from protoderm and ground meristem cells. During leaf development, young, active, and whitish colleters become brownish and inactive at late developmental stages. Alkaloids and phenolic compounds were common in central axis cells. A mixture of hydrophilic and lipophilic substances histochemically detected, which can prevent water loss under hot tropical climates, were also found. Secretion accumulation was observed in the periplasmic region of the secretory cells and in the subcuticular spaces. Cuticular pores were present especially in the apical portion of the colleters. Our data revealed some cellular aspects of the secretion mechanisms in the leaf colleters of C. burchellii. [ABSTRACT FROM AUTHOR]