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Folke Skoog: Influence Statistics

Geometric and position isomers of zeatin and of ribosylzeatin and other compounds closely related to zeatin have been tested in the tobacco (Nicotiana tabacum var. Wisconsin No. 38) bioassay. None was more active than zeatin itself. There was a much greater difference in activity (> 50-fold) between trans- and cis-zeatin than between trans-isozeatin [6-(4-hydroxy-2-methyl-trans-2-butenylamino) purine] and cis-isozeatin [6-(4-hydroxy-2-methyl-cis-2-butenylamino) purine], the latter being ...

It is well known that when the growing point of a young dicotyledonons plant is removed, the axillary buds lower down the stem grow out strongly, and eventually take the place of main stem. The presence of the terminal bud thus exercises an inhibiting action on the development of the lateral buds, causing them to remain dormant. To a smaller extent the leaves also inhibit the development of buds in their axils, as was shown by Dorsál (1909). The phenomenon has been studied by many ...

Sixty-nine compounds, mostly purine derivatives and closely related substances, were tested for promotion of growth and regulation of organ formation in the tobacco bioassay to determine relationships between chemical structure and cytokinin activity. Forty-three substances were synthesized in this study, and 13 of these were reported for the first time. N6-Alkyladenines (I) varied in activity over a wide concentration range depending on the length of the alkyl chain. Starting with ...

Cytokinin activity in the culture medium of four pathogenic strains of Corynebacterium fascians varied from 168 to 0.4 mug of kinetin (6-furfurylaminopurine) equivalents per liter, as compared to 0.2 in an avirulent control. N(6)-Isopentenyladenine was the predominant cytokinin in the medium of all five strains, and its increased production was correlated with the degree of pathogenicity; however, the virulent strains also produced 8-13 times more cis-zeatin ...

Pelet, F., A. C. Hildebrandt, A. J. Riker, and F. Skoog. (U. Wisconsin, Madison.) Growth in vitro of tissues isolated from normal stems and insect galls. Amer. Jour. Bot. 47(3) : 186—195. Illus. 1960.–In a preliminary analysis of the nature of gall formation induced by insects, a comparative study has been made of the in vitro growth and nutrition of plant tissues derived from insect galls and from normal plants. Grape, elm, poplar, and willow tissues were grown on a standard medium, ...

Transfer RNA from yeast, liver, and Escherichia coli has cytokinin activity in the tobacco callus bioassay, whereas ribosomal RNA from yeast is inactive. In contrast to fractions of yeast transfer RNA rich in serine acceptor and cytokinin activity, preparations (70 to 90 percent pure) of arginine transfer RNA(2), glycine transfer RNA, phenylalanine transfer RNA, and valine transfer RNA(1) and of highly purified alanine transfer RNA from yeast were inactive at concentrations of 20 to 2500 ...

Bioassays of tissue extracts show that high (500-1000 mug/liter) kinetin concentrations which permit growth of tobacco callus cultures on media without added thiamine activate the biosynthesis of this vitamin by the tissues. Although the tissue concentration of thiamine may fall appreciably, it is maintained at a level adequate for survival and slow growth of the cultures, and there is a large net increase in total thiamine content per culture with time. In the second and subsequent ...

The RNA base analogues, 2-thiouracil, 6-azauracil and 8-azaguanine incorporated singly into the medium, increased the number of floral buds in excised stem segments of Nicotiana tabacum variety Wisconsin No. 38 cultured in vitro. Combined treatments with 2 and 3 base analogues were even more effective. The effects were prevented by the corresponding natural counterparts, uracil, uridine, and guanosine respectively. These nucleic acid constituents added to cultures without base analogues ...

Compounds related to dihydrozeatin that define the influence of the location of the hydroxyl group along the side chain have been synthesized and tested for cytokinin activity. The compounds compared are in the series: 6-(X-hydroxy-3-methylbutylamino)purines and their ribosides, where X = 2, 3, and 4.Hydroxy substitution on the 4-position of the side chain enhances, but in the 2-, 3-, or 2- and 3- positions, decreases cytokinin activity as compared with the unsubstituted isopentyl (or ...

THE MAIN RESULTS PRESENTED IN THIS ARTICLE MAY BE SUMMARIZED AS FOLLOWS: 1. A test method with deseeded Avena seedlings for small concentrations of auxin and precursors of auxin has been described. 2. This method makes possible quantitative determinations of about ten times as low concentrations of hormone as can be obtained with the standard method, (a) Through an increase in the time of the test, so that nearly all the hormone applied can be utilized. (b) Through an increase in ...

This distribution of cytokinin activity in tRNA species of Escherichia coli has been determined. Cytokinin activity was restricted to tRNA species recognizing codons with the initial letter U. The following have been shown to contain a cytokinin: tRNA(Phe), tRNA(Leu) UUG, tRNA(Ser)UC(G) (A), tRNA(Tyr), and tRNA(Try). tRNA(Cys) was present in fractions with cytokinin activity but was not sufficiently pure to prove it to be active. One tRNA(Ser) UC(C) (U) species was inactive. All major ...

The incorporation of (14)C-2-mevalonic acid into transfer RNA and ribosomal RNA (high molecular weight RNA) in rapidly growing, cytokinin-dependent tobacco (Nicotiana tabacum var. Wisconsin No. 38) callus cultures has been investigated. Approximately 40% of the label incorporated into transfer RNA was present in a ribonucleoside with chromatographic properties identical to those of cis-ribosylzeatin. The remainder of the label in the transfer RNA appears to be nonspecific incorporation ...

Pith tissue was cultured on modified White’s nutrient medium supplemented, except for controls, with 2 mg/l of IAA and/or 0,5 mg/l of kinetin. For autoradiographs sections were used from tissue grown on medium containing tritiated thymidine.Nuclear DNA contents (Feulgen) were measured by the microspectrophotometric two-wavelengths method. No fading of Feulgen dye in nuclei was found in 11 weeks, in contrast to considerable fading observed in earlier work when a different batch of basic ...

The esters of the highly active cytokinin zeatin [6-(4-hydroxy-3-methyl-trans-2-butenylamino) purine] with formic, propionic, and indole-3-acetic acids and of its 2-chloro-substituted derivative [2-chloro-6-(4-hydroxy-3-methyl-trans-2-butenylamino)purine] with acetic and propionic acids have been synthesized, and their growth-promoting activities in the tobacco bioassay have been determined and compared with those of four known, related compounds: zeatin, ...