Degeneration of the Salt Glands Accompanying Foliar Maturation in Avicennia Marina (Forsskål) Vierh

Summary The salt excreting glands on both the adaxial and the abaxial surfaces of a sequential developmental series of leaves of Avicennia marina were studied at the light microscopic and ultrastructural level. Scanning electron and light microscopy have shown that there is a decrease in the total number of glands on the adaxial and abaxial surfaces as the leaf matures. From transmission electron microscopy it was established that the glands of emerging, unexpanded leaves exhibited most of the cytological features common to gland cells of all plant species. However, as the leaf expanded, the gland cells were observed to autolyse and the entire glandular structure to collapse. This loss of structural integrity of the glands coincided with abaxial stomatal development and the shift of salt excretion to this surface.