Translocation in Sugar-beet: I. ASSIMILATION OF 14CO2 AND DISTRIBUTION OF MATERIALS FROM LEAVES

¹⁴CO₂ was supplied to leaves, and movement of labelled carbonto other parts of the plant was assessed. Young growing leavesutilized assimilated carbon for their own growth and did notexport carbon to the rest of the plant, while fully expandedleaves exported much of their photosynthate, both to root andto young leaves. Translocation from a particular leaf was tothe two or three younger leaves on the same side of the plant,and to a sector of root below the source leaf. Specific distributionto growing leaves could be modified by partial defoliation.There was no movement of material to leaves which had emergedbefore the source leaf. Part of the carbon entering a leaf by assimilation (and, foryoung leaves, by translocation) was incorporated into insolublematerial, especially in young leaves. Some of the carbon enteringa developing root was permanently stored as sucrose, althoughmuch also entered insoluble material. Loss from the leaf ofcarbon fixed during a short period of photosynthesis was rapidat first but continued at a decreasing rate for several days.Some carbon fixed into the insoluble fraction was translocatedfrom the leaf later, during senescence. Sucrose was the mainmaterial translocated immediately after photosynthesis.