EVIDENCE OF DOWNWARD TRANSPORT OF 'SOLANACEOUS' ALKALOIDS* BY PAMELA M. WARREN WILSON

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1 EVIDENCE OF DOWNWARD TRANSPORT OF 'SOLANACEOUS' ALKALOIDS* BY PAMELA M. WARREN WILSON Botany Department, University of Reading {Received 5 November 1958) (With Plate 6 and i figure in the text) It IS now well known that the 'solanaceous' alkaloids characteristic oi Atropa belladonna L. and Datura stramonium L. are synthesized mainly in the roots and move upwards through the plant in the transpiration stream. Experiments with grafted plants of Atropa belladonna (Warren Wilson, 1952) have provided some evidence of downward transport of these alkaloids when they are introduced into another species which is normally free of them. Thus, no part of a tomato plant normally contains 'solanaceous' alkaloids, which give the Vitali colour reaction, but they have been recovered from the roots of a tomato plant growing some distance below an approach-graft of the tomato stem with an A. belladonna stem. In one case a bridging-graft (Fig. i) was Fig. I. Diagrams to show the arrangement of a bridging-graft. A, stems cut and flaps ready for tying; B, flaps united, about 2 weeks after grafting; a, tomato stem; b, Atropa or Datura stem; f, callus formed over exposed cut surfaces. arranged to allow transport from A. belladonna to tomato in a morphologically downward direction only; 'solanaceous' alkaloids were again recovered from the tomato roots. Within this a brown scar line separated most of the parenchyma of the two pieces of stem involved, but the two half-cylinders of vascular tissue were completely joined * This work was carried out during the tenure of the Huntley & Palmers Agricultural Research Fellowship at the University of Reading. 326

2 Transport of alkaloids 3 27 in the middle of the bridge. It was concluded that 'solanaceous' alkaloids had crossed the bridge in a downward-flowing stream in vascular tissue, in all probability in the phloem. This paper concerns a number of tomato plants, each joined to an A. belladonna or Datura stramonium plant by a bridging-graft, and sampled at intervals from May to September. Progressive accumulation of 'solanaceous' alkaloids in the tomato plants strikingly confirms the first, limited observation of bridging-grafted plants. In addition the graft s were examined anatomically. METHODS Five bridging-grafts between tomato (Best of All) and D. stramonium were made on 28 April 1952; four bridging-grafts between tomato (Bonny Best) and Atropa belladonna were made on 10 May The bridges were formed by tying an upward-pointing flap of tomato stem to a downward-pointing flap of Datura or Atropa stem with the cut surfaces in contact (Fig. i). They soon became firm and hard, and the bast tying them was finally removed 10 to 16 days after grafting. The plants were grown on John Innes compost No. 3 in a sunny greenhouse. Flowers and fruit were removed about once a month, and in June the tomato tops of the last two Datura : tomato pairs were cut back to two axillary shoots as the plants became unwieldy. At sampling, soil was thoroughly washed from the roots with a jet of water. The plants were then divided and dried for 24 hr at 60 C in a forced draught oven, and stored in screw-topped jars. Before analysis for total 'solanaceous' alkaloids (calculated as hyoscyamine) by the modified Allport and Wilson technique already described (Warren Wilson, 1952), samples were redried for hr at 55-6o C. The dry weights of most of the root systems were corrected for any adhering soil by ashing samples of root powder. The graft s were preserved in 60')o alcohol. Weeks from grafting Total 'solanaceous' alkaloids (mg) Table i. Datura stramonium: tomato (Best of All) bridging-grafts None Tomato stem -f roots None None Trace si Trace -\ Trace H / 1.36 stem \o.94 roots Dry weight (g) Tomato stem roots 0.34* * * / 1.94 stem \ roots Alkaloid assay (" dry weight) Note. Tomato shoot abo\ t- gralt Tomato stem - roots o ooo D. sliaiiujiiiiini shoot abw\f graft 0.24 D. strami»iiuni stem roots 'f race * Not corrected for adhering soil. Trace Trace O.OI I Seven weeks after grafting, the tomato tops were cut back to two axillary shoots stem root^

3 328 PAMELA M. WARREN WILSON RESULTS AND DISCUSSION The results of alkaloid analysis are given in Tables i and 2. In both series of grafts the tomato stem and roots below the graft contained increasing amounts of alkaloids with increasing length of time from grafting. In the Datura series the amounts were small: traces only up to 5^- weeks, 1.88 mg at 11 weeks and 2.30 mg at 19 weeks after grafting (Table i). Larger accumulations of alkaloids were found in the corresponding parts of the tomato plants grafted with Atropa, reaching as much as mg 17^ weeks after grafting. Assay figures ('^n dry weight) for tomato stem and roots of the Atropa series also increased up to o.i94';'o (last sample), which approaches the figure of 0.26% tound for the Atropa root system (Table 2). The tomato roots of the last Atropa : tomato pair had grown out through the pot's drainage hole into the gravel on the greenhouse bench. These young roots were analysed separately from those in the pot; although furthest from the bridging-graft they contained 5.58 mg alkaloids and gave an assay of 0.236%, the highest of the series. There can thus be no reasonable doubt that 'solanaceous' alkaloids continued to cross the bridging-graft s and were translocated in a morphologically downward direction during the whole summer. Down\\ard transport was followed by some upward movement into the tomato shoots, for, towards the end of the growing period, small amounts of alkaloids were found in the tomato shoots above the graft s of both series. Weeks from grafting Total 'solanaceous' alkaloids (mg) Table 2. Atropa belladonna: tomato [Bonny Best) bridging-grafts None Tomato stems + roots 0.8^ } None None s stem roots in pot 5.58 protruding roots Dry weight (g) Tomato shoot abo\'c graft Tomato stem f roots * roots in pot 2.37 protruding roots Alkaloid assay (' dry weight) Tomato stem + roots A. belladunnn shoot abo\'e graft A. belladoiuia stem + roots * Chiefly stem; most leaves abscissed. t Not corrected for adhering soil stem roots in pot protruding roots 0.27 Anatomical study showed that vascular continuity had already been established between the two halves of the bridging-graft s at the time when the first samples were taken for alkaloid analysis, ahhough at this stage the scar line was nearly continuous across pith and cortex. In older graft s a considerable amount of secondary phloem and xylem had been formed from the united cambia, and the scar line, though

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5 Transport of alkaloids 329 broken in places by proliferated parenchyma, was still apparent. There is thus a strong suggestion that alkaloids were transferred from Datura and Atropa to tomato m vascular tissue of the bridging-graft s. Since a long-term transfer in a downward-flowing stream took place, the 'solanaceous' alkaloids were probably transported in the phloem. A detailed account of bridging-graft anatomy will be published separately. REFERENCE WARREN WILSON, P. M. (1952). Formation and transport of alkaloids in solanaceous grafts. New Pliytol., EXPLANATION OF PLATE 6 Phot. I. Bridging-graft between tomato and Datura stramonium a few days after grafting. Phot. 2. Bridging-graft between tomato and Atropa beltadonna about 3 weeks after grafting.

Stems and Transport in Vascular Plants. Herbaceous Stems. Herbaceous Dicot Stem 3/12/2012. Chapter 34. Basic Tissues in Herbaceous Stems.

Stems and Transport in Vascular Plants. Herbaceous Stems. Herbaceous Dicot Stem 3/12/2012. Chapter 34. Basic Tissues in Herbaceous Stems. Bud scale Terminal bud Stems and Transport in Plants One year's growth Terminal bud scale scars Axillary bud Leaf scar Node Internode Node Chapter 34 Lenticels Terminal bud scale scars Bundle scars A Woody