Natural Cytokinins Research Articles

CALLUS GROWTH AND ROOTING OF CASSAVA (MANIHOT ESCULENTA CRANTZ) STEM SEGMENTS CULTURED IN VITRO

SUMMARY With the in vitro culture of cassava tissue the optimum sucrose level for callus growth is lower than that for the initiation and growth of roots. Auxin and cytokinin both promote callus growth, the latter by inducing cell division, the former also by stimulating cell elongation. In subcultures cytokinins are obligatory for callus growth, the natural cytokinins, zeatin and 2iP, yielding green tissues. Organ development never occurred in these subcultures. Auxin (NAA) is required for the initiation and growth of roots on the callus. Different cytokinins reduce this rooting effect in various degrees without, however, inducing the initiation of shoot primordia.

Effects of different cytokinins on the senescence of detached oat leaves

Senescence is delayed (chlorophyll retained) in oat leaf sections by kinetin and benzyladenine, but not by the natural cytokinins, zeatin and isopentenyladenine.

Cytokinins in Seeds of Pumpkin

Extracts of seeds of pumpkin (Cucurbita pepo Linn.) contain three chromatographically distinguishable cytokinins which are held on Dowex 50-W and are extractable by ethanol and n-butanol. Two of the active factors are precipitable by silver nitrate at acidic pH. The chromatographic behavior and the spectral characteristics of one of these cytokinins are similar to those of zeatin. However, the R(F) values of the other two active compounds do not match with those of any of the known natural cytokinins.

Occurrence of Natural Cytokinin in Potato Tuber

The present investigation was undertaken to confirm the presence of the endogenous natural cytokinin (s) in the potato tubers. The methanol extract of potato tuber was separated by ascending paper chromatography using n-butanol: acetic acid: water (12:3:5) solvent system. Several violet or blue fluorescent spots on the test strip of chromatogram were detected by UV-lamp, and two of them (Rf 0.40-0.50 and Rf 0.55-0.60) not only reacted positively by Vischer's reagent but showed strikingly absorption by the UV-lamp at 260mμ. Accordingly, one (Rf 0.40-0.50)is nucleotide and the other (Rf 0.55-0.60) is a kind of the purine derivatives. While the addition of the former fraction to the medium exerted no significant influence on the tobacco callus growth, a marked stimulation of its growth was observed due to the latter fraction. As to the effect of the fraction (Rf 0.55-0.60) on the potato tissue culture, this factor not only resulted in likewise stimulation of callus growth but enchanced to elicit the root formation at its relative high concentration. Consequently, this factor closely resembles kinetin in its cytokinin activity. It was also ascertained a considerable cytokinin activity in this factor by means of the chlorophyll-retention assay using the barley leaf section. These results are interpreted to indicate, therefore, that there is a endogenous natural cytokinin in the potato tubers.

Isolamento Di Citochinine DalRhizobium LeguminosarumFrank

Abstract Isolation of Cytokinins from « Rhizobium leguminosarum » Frank. — Three substances with cytokinin activity have been isolated from liquid cultures of Rh. leguminosarum by fractionation on Dowex 50W X4 H+ column, butanol extraction, silver precipitation, chloroform extraction and finally by paper chromatography. The Rf-values and the U.V. absorption maxima of one of these substances were similar to those of isopentenyl adenine, a potent cytokinin synthetized by several bacteria responsible, as Rhizobium, for profound morphological alterations of the tissues of higher plants. The other two substances are not comparable to any of the as yet known natural cytokinins. It is suggested that these substances, produced by Rhizobium, are responsible for tissue proliferation during nodule formation.

Cytokinins in ribonucleic acids.

COMPOUNDS which, like kinetin (6-furfurylaminopurine), induce cell division in certain excised plant tissues have been termed cytokinins1. A number of synthetic substances (6-substituted purines, 1-substituted adenines and urea derivatives) show this characteristic. The most active natural cytokinin so far discovered is also a substituted purine, termed zeatin [trans-6-(4-hydroxy 3-methyl but 2-enyl) aminopurine]. This was isolated from Zea mays seeds2. Other natural cytokinins, as yet unidentified, occur in many other plant tissues, but there have been no reports of the occurrence of cytokinins as natural constituents of animal tissues. This communication, however, provides evidence that compounds with cytokinin activity are natural constituents of animal soluble RNA.