Piper regnellii has two types of trichomes: pearl glands and sac-like trichomes. Both secretory trichomes originate from the protoderm of the leaf primordium and reach maturity in the young leaves found in the shoot apex. The pearl glands are more abundant on the abaxial surface, while the sac-like trichomes cover completely both young leaf blade. The density of both trichomes decreases during blade expansion, being scarce in the adult leaf. The pearl glands are composed of a basal cell and an apical cell whose shape ranges from semi-globular to spatula-like. Secretion release occurs after rupture of the distended cuticle. The sac-like trichomes are composed of a basal cell, 1-2 stalked cells and an apical conical cell parallel to the leaf surface. The secretion is accumulated in minute subcuticular spaces. No cuticular ruptures have been observed.
Piperaceae; Piper regnellii; ontogeny; glandular trichomes; secretion
