Quantitative photoperiodic control of erect thallus production in Sargassum muticum

Most of the photoperiodic responses result in a sharp contrast between development in long and short days, so that qualitative observations are quite sufficient to establish that development is under photoperiodic control, and qualitative information of this type is all that is available for many of the responses (Dring 1984). However, we need to devise some quantitative measurement of the response in order to study the physiological mechanism of photoperiodic control. We report here the quantification of photoperiodic control of erect thalli production of Sargassum muticum in different daylength regimes. (omitted)