Development, structure, and secretion of leaf colleters in Clusia criuva Cambess. subsp. criuva (Clusiaceae)

ABSTRACT

Colleters produce a secretion composed of hydrophilic and/or lipophilic substances which lubricates and protects the shoot apical meristem against biotic and abiotic agents. Little attention has been given to these structures in Clusiaceae. In the present study, the structure and development of the leaf colleters of Clusia criuva subsp. criuva were described and variations in the exudate composition of the colleters at different stages of leaf development were identified. The samples were collected and processed according to techniques for light and scanning electron microscopy. Colleters are of the standard type and not vascularized, and during leaf development, changes in color, structure, and secretion abundance were observed. Asynchrony in the development was noticeable in the leaf primordia and young leaves, from colleters in early formation to those in early senescence. In early phases there was an abundance of polysaccharide, lipid, and protein secretions, whereas adult and senescent leaves revealed an accumulation of phenolic compounds and cell degradation. The secretion was released by the rupture of the cuticle. The structural changes and secretion composition during leaf development emphasize the role of colleters in protecting meristems and developing organs.

Keywords:
exudate; glands; histochemistry; Malpighiales; morphoanatomy