The Ultrastructure of the Digestive Glands in Pinguicula vulgaris L. (Lentibulariaceae) Relative to their Function. I. The Changes During Maturation

Abstract

The digestive glands of Pinguicula vulgaris become fully mature whilst still enclosed in the bud. All the gland cells remain intact on the fully expanded unstimulated leaves. As the secretory head cells mature, a special layer forms between the plasmalemma and the cell wall. This layer is shown to be different from the typical labyrinthine wall of transfer cells and serves for the storage of digestive enzymes. Ultrastructural analysis, including morphometry, indicates that the digestive enzymes are synthesized on the RER of the head cells and transferred into the cell wall, particularly into the slime layer, and vacuoles. This transfer is achieved firstly through continuity of the endoplasmic reticulum with vacuoles (static) and the periplasmic space (dynamic) and, secondly, into the latter through exocytosis of coated Golgi vesicles and of some vacuoles filled with enzymes.