Abstract: Subcellular localization of IAA in the leaf cells of Vicia faba L. was studied with immuno-gold electron microscopic technique. Nuclei and chloroplasts in mesophyll cells of the immature leaves were labeled with nuinerous gold particles, which were also seen in the cytoplasm and cell wall. In mesophyll cells of the mature leaves, gold particles were mainly distributed over the chloroplasts and cytoplasm, and a few were also located in the cell wall; but, however, none was seen in the vacuoles. Many gold particles were distributed over the phloem cells of the fine veins of the mature leaves, and were mainly located in the cell wall of the transfer cells. Some were also located in the cells of vascular bundle sheath of the fine veins, mainly distributed over the chloroplasts, cytoplasm and cell wall. Sections of mesophyll cells of the immature leaves without EDC ( 1- ethyl-3 (3-dimethylamino-propyl) carbodiimide) fixation or treated with normal rabbit IgG instead of anti-IAA rabbit serum were devoid of gold particle label. Tissue and subcellular immuno-localization of IAA and its physiological significances were discussed.

Key words: IAA, Colloidal gold immuno-localization, leaf cell