The Translocation of 11C-labelled Photosynthate in the Soybean

The movement of photosynthetically incorporated carbon downthe stem of soybean plants has been studied in vivo using carbondioxide labelled with the short-lived isotope ¹¹C. The rateof accumulation of radioactivity at several points in the stemwas measured during continuous illumination. This accumulationrate quickly became constant and remained so for at least severalhours. The effects of stopping photosynthesis, of removing thelabelled carbon dioxide, and of different light pretreatmentsof the plants were investigated. The results are discussed interms of a flow translocation process and a pool of labelledphotosynthate in the upper part of the plant.