Influences of Stock and Scion on Alkaloid Synthesis and Transformation

Abstract

It is desirable and necessary to reexamine the influences of stock andl scion oIn alkaloid synthesis and transformation using plants which behave differently witlh respect to alkaloid formation (4). Experiments were conducted in the greenhouse for 3 years in an attempt to separate the effects of root, or stock, from those of the top, or scioIn, on alkaloid synthesis and transformation. Some of the grafting combinations reported in this paper resenmbled those prepared previously by Dawson (2), but plants witlh various degrees of ability in alkaloid synthesis were included in this study. Materials and MethodsThe following plants were used in these experi- shadle at high moisture levels for several days after cutting as the conductive system throughl the graft was unable to carry the loadl of normal transpiration. The nitrogen supply of the planits was kept at a minimuml until the original roots of the scion were removed and was then raisedl to encourage alkaloid syntlhesis. Some of the excised tops were analyzed to providle an estimate of the alkaloid already present in the tops of alkaloid synthesizing species when they were cut loose from their own roots and left on a stock of a practically nonalkaloid-synthesizing plant like tomato.The plants were not decapitated, and were harvested after 9 to 11 weeks. Only the tops, including 1

The Only African Wild Tobacco, Nicotiana africana: Alkaloid Content and the Effect of Herbivory

“…However, the synthesis of nornicotine is secondary; it is the demethylation product of nicotine [18] . Nicotine is synthesized in the roots and transported to the leaves whereas nornicotine is produced in the roots and leaves [48] . Possible reasons for nicotine accumulation in leaves in response to herbivory in N. africana , and we stress that these are speculative, could be that nicotine was not yet converted to nornicotine, or that the production of nicotine as defense in nornicotine-dominated plants may lower the cost of defending the plant against herbivory, due to saving on nornicotine biosynthesis costs.…”