Possible modes of salt secretion in avicennia marina in the sinai

Avicennia marina salt glands were studied by scanning electron microscopy (SEM), in order to relate their ultrastructure to the extracellular salt secretion process. It was found that a multiphase asynchronous process regulates the salt secretion. In the light of the present study and previous evidence we describe two mechanisms of salt secretion. The first mechanism is a merocrine one, consisting of the formation of a vesicle that expands until it reaches a maximal size, when it bursts, releasing the salt solution. Later the burst vesicle disintegrates and a new one begins to form. The second suggested mechanism is an holocrine one and begins with the accumulation of the secreted solution in the subcuticular space. This results in the tearing of the cuticle and the release of the salt solution as droplets. The first suggested mode of secretion operates regularly, while the second one takes place only occasionally.