Structure and development of the secretory cavities of Myrtus communis leaves

The structure and development of Myrtus communis L. secretory cavities has been studied in young and expanded leaves, using light and scanning electron microscope. Secretory cavities are continuously formed during leaf development, but in mature leaves the rhythm of their appearance shows steep decrease. Each secretory cavity is developed from a single epidermal cell, which undergoes a periclinal division followed by anticlinal and several oblique cell divisions. The lumen of the secretory cavity is initiated by cell wall separation, i.e., schizogenously. The secretory cells line the cavity, where the secreted material is collected. Secretory cavities are covered by modified epidermal cells, which do not seem to form any special aperture. Essential oils seem to be discharged after mechanical treatment of the leaf.