Effect of light on the metabolism of thymidine in the long-day duckweed, Lemna gibba G3

Metabolism patterns of exogenous thymidine as disclosed by ECTEOLAcellulose column chromatography, were examined with a long-dayduckweed, Lemna gibba G3, under dark and light conditions. Whenthymidine-6-³H was applied, the pattern of thymidine metabolismin the light was not very different from that in the dark. However,when thymidine (methyl-³H) was used, incorporation of radioactivityinto two major ( and ß) and one minor components ofboth B and D fractions separated by column chromatography, wasstrikingly stimulated by the light, through photosynthetic activity.Component a of fraction B was tentatively concluded to be ß-ureidoisobutyricacid by paper chromatography. As the radioactivity from thymidine-6-³Hwas hardly recovered in the a component of fraction D, the partof the thymidine molecule incorporated into this component wasnot the pyrimidine ring, but a methyl residue. (Received March 29, 1973; )