Calibrating duckweeds: light, clocks, metabolism, flowering

The roles of photoperiodism and related light-dependent and hormonal processes in plants are not well understood. Rapid growth, aquatic habit, and adaptability to axenic culture make the Lemnaceae, or duckweeds, excellent material for investigating these topics and others in which highly defined conditions or the presence of organic substances are crucial. As a major example among several that are described, recent work with one species suggests a relation between some features of carbon dioxide flux and the photoperiodic timing mechanism, thus providing a system in which the biochemical basis of the latter may be explored.