Production, Translocation and Accumulation of Alkaloids in Tobacco Scions Grafted to Tomato Rootstocks.

The remarkably low alkaloid content of whole tobacco shoots grown as scions on rootstocks of lowalkaloid species has been recorded by many investigators (cf. Dawson (5), James (8), and Mothes (10) for reviews). Although the data of Tso and Jeffrey (14) appeared to be in contradiction, the disagreement has since been resolved (see below). Solt (13) demonstrated that low alkaloid content in this material could not be the result of an interaction between substantial rates of synthesis and destruction. Consequently, the earlier explanation (4) involving a low intrinsic rate of alkaloid production in the shoot was accepted. Solt (13) also described the distribution of alkaloid in grafted shoots preparatory to an analysis of the marked disparity in alkaloid synthesizing capacities of root and shoot. The present paper describes the changes in such distribution brought about by removal of the apical bud (topping), defoliation, topgrafting and approach-grafting, respectively, of scions of two varieties of tobacco grafted to tomato roots. Deductions are drawn regarding the probable locus of synthesis, currents of transport and major sites of accumulation of alkaloid in the system tobacco scion-tomato rootstock.