Ultrastructural development and secretion in the salt glands ofTamarix aphylla L.

The functionally integratedTamarix salt gland consists of four piled pairs of cells, the three upper pairs of which constitute the main secretory cells while the lower pair corresponds to the so-called collecting cells. The whole gland is surrounded by the cuticle except for an area in the common wall between the inner secretory cells and the collecting cells (transfusion field). Each salt gland originates from a single protodermal cell with typical ultrastructure of a meristematic cell. In the progress of gland development no remarkable ultrastructural alterations occur in the secretory cells up to the stage of secretion. Since the secreted salt does not react with osmium tetroxide, the stage of secretion was estimated mainly on the basis of the mode of development of the subcellular structures considered to play an important role in the secretory process (wall protuberances, transfusion field, subcuticular space, small vacuoles, and mitochondria).