XVI International Botanical Congess

Chloroplasts in epidermal cells of the aquatic monocot Vallisneria gigantea accumulate on the periclinal layer of cytoplasm (P side) under dim light and on the anticlinal layers of cytoplasm (A sides) under strong light. Red light first induced a rapid acceleration of randomly-oriented movement of chloroplasts, and then an almost complete loss of motility of the chloroplasts. The configuration of bundles of microfilaments (MF) on the P side changed from a random network to a striking honeycomb array concomitantly with the loss of motility of chloroplasts. In contrast, blue light induced a unidirectional movement of chloroplasts from the P side to the A sides within a few minutes. In these cells, the MF bundles on the P side became thicker and aligned in a straighter way.