INCORPORATION OF RADIOACTIVE CARBON FROM H<sup>14</sup>CO<sub>3</sub><sup>−</sup>INTO SUGAR CONSTITUENTS BY A BROWN ALGA, <italic>EISENIA BICYCLIS</italic>, DURING PHOTOSYNTHESIS AND ITS FATE IN THE DARK<xref ref-type="fn" rid="fn1"><sup>1</sup></xref><xref ref-type="fn" rid="fn2"><sup>2</sup></xref>

Abstract

When the fronds of Eisenia bicyclis were exposed to H14CO3− in the light, the radioactive carbon was rapidly incorporated into mannitol. Even after illumination of such a short period as 5 min, about seventy percent of the total radioactivity incorporated was found in this compound, and the specific radioactivity of this alcohol decreased very rapidly during the subsequent dark incubation. Among various cellular polysaccharides examined, only laminaran showed a similar quick response with respect to the specific radioactivity change. On the basis of these findings it was concluded that mannitol and laminaran form storage substances in the brown alga, and they are possibly interchangeable as sucrose and starch do in higher plants.