The aril of Chamaecytisus proliferus (L.fil.) Link (Leguminosae): its structure, histochemistry and role in the dispersal and in water-seed interaction

The aril structure and histochemistry of Chamaecytisus proliferus seed were investigated by bright-held and fluorescent light microscopy, and scanning electron microscopy. The aril consisted of three different regions; a loose peripheral tissue composed of large cells; a median region composed of closely packed elongated cells lying parallel to the axis ridge-lobes; an inner region composed of thick-walled cells close together and orientated perpendicularly to the same axis. These structural features of the aril and the occurrence in it of many different substances detected by toluidine blue O, alcian blue at low pH (polysaccharide hydrophilic substances), by iodinepotassium iodide (starch), naphthol blue black (proteins) and fluorol yellow (lipids) suggested a multipurpose role of the aril regarding the main functions of the seed: germination and dispersal. In particular the nutrient composition of the aril, due to the presence of starch, proteins and lipids, might be related to dispersal by ants (myrmechory), whereas the aril cell walls, rich in polysaccharide substances, might be involved in germination acting as a site of apoplastic absorption of water.