Search

The prolongation of the effect of exogenous cytokinins by inhibition of their inactivation was studied in Raphanus sativus L. cv. Rampouch. As in radish the main way of cytokinin inactivation is their N-glucosylation, inhibitors of this pathway, papaverine, theophylline and olomoucine, as well as two olomoucine analogues, bohemine and roscovitine, were tested. The latter ones, which function as potent inhibitors of cyclin-dependent kinases, have also been found to effectively inhibit cytokinin N-glucosylation. Incubation (24 h) of de-rooted radish seedlings with inhibitors resulted in c. 50% decrease of the conversion of model cytokinins, [3H]dihydrozeatin and [3H]N6-benzyladenine, to the corresponding 7 N-glucosides. Simultaneously the level of the non-metabolized cytokinin bases was elevated. The activity of cytokinin oxidase/dehydrogenase (EC 1.5.99.12) was suppressed in a dose dependent manner. The concentration of physiologically active endogenous cytokinins was not increased significantly by inhibitor application. The inhibition of N-glucosylation was in the case of olomoucine, bohemine and roscovitine accompanied by the accumulation of physiologically nonactive cis-zeatin derivatives. The impact of inhibitors on the endogenous cytokinin pool seems to be balanced by the mechanisms involved in the maintenance of cytokinin homeostasis. [ABSTRACT FROM AUTHOR]

Influence of continuous supply with a solution of glucose on the changes in the content of soluble sugars and proteins in various organs of the cut rose (Rosa hybrida cv. Carina). Exogenous glucose continuously supplied to the cut rose is immediately converted into saccharose in the stem tissues. This saccharose migrates to the flower, where it is immediately hydrolysed, and to the leaves where its hydrolysis occurs more slowly. The reducing sugars resulting from the hydrolysis of saccharose in the flower and, therefore, possibly from the hydrolysis of saccharose in leaves, induce a large accumulation of hexoses (glucose and fructose) in the flower. The protein content does not depend on the level of reducing sugars in the flower.

Although quantitative differences were observed in the cytokinin content of mature leaves and bark of Salix babylonica it would appear as if these tissues contained the same cytokinin complement. Ringing resulted in a decrease in the level of cytokinins in the leaves and an increase in the bark, both above and below the girdle. In the leaves the decrease was due mainly to a drop in the level of those compounds that co-chromatographed with the cytokinin glucosides. These compounds were also almost undetectable in the bark above the girdle, where callus was formed. The observed increase in the cytokinin content of the bark above the girdle was due to higher activity in those parts of the chromatograms where zeatin and zeatin riboside occurred. Ringing stimulated the growth of lateral buds below the girdle. These developing buds as well as the bark below the girdle contained very high levels of cytokinins that co- chromatographed with zeatin and zeatin riboside. [ABSTRACT FROM AUTHOR]

During the cellular activation that begins with excision of root explants from Cichorium intybus L. var. Witloof cv. Zoom cultured in vitro, hydrolysis of fructose polymers, in particular of the polyfructosans (inulin) takes place. The products of degradation are used to cover the energetic needs connected with the increase of the mitotic activity. After day 2 the intracellular carbohydrates (sucrose and reducing sugars) develop differently according to further development of the explants. When growth of unorganized callus is favoured and organ formation inhibited by medium supplemented with auxin, fructose is accumulated; but under bud‐forming conditions it is the amount of sucrose that increases. These differences were most notable between days 3 and 10 in culture, the period during which primordia occurred in the shoot‐forming callus.

Indolyl‐3‐butyric acid and vitamin D3 enhance adventitious root formation in green cuttings of Populus tremula L. A significant synergistic effect is observed between these two substances. The number of roots formed on application of the individual substances and on simultaneous application depends on the growth substance concentration, the timing of application, the age of the cuttings and the number of leaves. Of the vitamin D3 animal metabolites tested, only 1,25‐dihydroxyvitamin D3 markedly promoted adventitious rooting, and this to a lesser extent than vitamin D3 itself. The 3‐O‐glucopyranosides of vitamin D3 and the vitamin D3 animal metabolites, promoted rooting to the same extent as the parent compounds. [ABSTRACT FROM AUTHOR]