Ricinine translocation

Interpretations of the above two results were complicated by the fact that the radioactivity ratio between ricinine and its demethylated forms did not necessarily indicate the ratio of translocated forms since the demethylated form of ricinine upon arrival to the green leaf from the yellow leaf may undergo methylation. The result showed that ricinine administered in the yellow leaves was translocated to healthy parts of the plant, especially the growing apex where ricinine is actively synthesized. The result supports the idea that a ricinine translocation process might be a salvage operation performed by the plant in order to reutilize ricinine from the leaves which are being prepared for abscission. This is a broad concept of... 

When ricinine-3,5- C was administered to castor by way of the stem, it was found that the alkaloid was translocated to the seed [6]. It was also shown that ricinine-3,5- C was converted to respiratory 002 both in the dark and in the light [6]. 

Figure 4.4b. Radioactive ricinine infiltrated into Ricinus communis shoots distribution of the label versus time (Nowacki and Waller, 1975). Courtesy of the authors and the Society of Translocation and Accumulation of Nutrients in Plant Organisms, Warsaw.

Figure 4.5. Translocation of ricinine in young rootless plants after it was added to rootless plants. Middle—distribution of radioactive ricinine after 10 hr (time required for [8- C]-ricinine to be taken up). Top—distribution of radioactive ricinine after an additional 48 hr. Bottom—distribution of ricinine in plants poisoned with p-aminobenzaldehyde after 70 hr. Numbers indicate percentages of radioactivity recovered (Nowacki and Waller, 1972). Courtesy of the journal.

Waller and Skursky (1972) showed that [3,5- C]ricinine administered to senescent leaves of the castor bean plant, Ricinus communis, was translocated to all other tissues of the plant the developing fruit and especially the seeds were found to be labeled the most rapidly. For further discussion of the subject, see page 206. 

Table 6.4. Demethylation and Translocation of [3,5- C]Ricinine from Yellow Leaf to Green Leaf of Castor Bean Plant Cuttings ...

Figure 6.15 shows the demethylation and translocation of [3,5-ricinine administered to a yellow leaf attached to the lower part of the stem of a mature castor bean plant. The radioactivity of ricinine and the... 

Figure 6.15. Demethylation and translocation of [3,5- K ]ricinine from the yellow leaf to the adjacent green leaf of the castor bean plant cutting with one green and one yellow leaf, a— Ricinine in yellow leaves b—demethylated ricinines in yellow leaves c—ricinine in stems d—demethylated ricinines in stems e—demethylated ricinines in green leaves /—ricinine in green leaves g— green leaf h—yellow leaf (Lee and Waller, 1972). Courtesy of Peigamon Press, Ltd., copyright 1972.

Ricinine is obviously translocated via the phloem tissue, since its movement via xylem would result in accumulation in the large older leaves (Crafts, 1961). There is a possibility that ricinine passively accompanies other metabolites from leaves to sinks or sites of utilization moving along by mass flow. However, the reason for its intense export from leaves prior to abscission remains unclear. Perhaps this alkaloid is eventually utilized for the synthesis of, or controls the synthesis of, compounds in or closely related to the pyridine nucleotide cycle (Waller et al., 1966). 

The facts that the plant translocates ricinine away from senescent leaves to young, developing tissues and that it is abundant in young tissues suggest that this compound has a specific physiologic or metabolic function in growth. A mere waste product of metabolism would hardly be transported into seeds and other vitally important tissues from a leaf which was to be lost by abscission. 

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