The translocation of 14C-sucrose to the different parts of the mustard (Brassica juncea) crop has been evaluated in the context of understanding the source to sink relationship in the thiol-induced enhanced crop yield. The foliar application of thiols like TU, TGA and DTT to the plant gave maximum sucrose phosphate synthase activity, which was found to have direct correlation with the movement of sucrose. The distribution pattern of 14C-sucrose follows the path from internode and node to pod via leaf. The translocation of 14C-sucrose was found to be a light dependent process. Among the nucleotides ATP and GTP, only ATP was able to promote the translocation and GTP was ineffective. In this unique in situ tracer experiment using 14C-sucrose, we could establish that thiols are able to enhance the translocation of sucrose from source to sink.