Electrical properties of the salt gland of Aegiceras

Microelectrode and current clamping techniques have been used to investigate the electrical properties of the salt gland of Aegiceras corniculatum Blanco. Three regions of the gland corresponding to the cuticular cap, secretory cells, and the basal cell are distinguishable according to their resting potential and voltage response characteristics. The resting potentials of the secretory cells and basal cells are shown to be markedly negative with respect to the cuticular cap and the surface of the gland. Penetration of the base of the gland always results in a sharp drop in the resting potential. It is also shown that there exists a low resistance pathway from the cuticular region to the underside of the gland which shunts the secretory cells, and that the cuticular cap presents a high electrical resistance. The resting potential and voltage response at various positions in the gland were also measured with variation in leaf illumination. It is shown that the resting potential becomes less negative throughout the gland for the transition light to dark. A similar change in illumination generally produces a rise in voltage response.