Zeatin Glucoside Research Articles

Endogenous Phytohormones of Fern Polystichum aculeatum (L.) Roth Gametophytes at Different Stages of Morphogenesis in vitro Culture

The content of indole-3-acetic (IAA), gibberellic (GA3), abscisic acids (ABA), and cytokinins—zeatin (Z), zeatin glucoside (ZG), zeatin riboside (ZP), isopentenyladenin (iР), and isopentenyladenosine (iРА)—was determined using the method of high-performance liquid chromatography in fern Polystichum aculeatum gametophytes at different stages of morphogenesis in vitro culture. It was shown that, at the stage of spatulate prothallium development, gametophytes contained significant amounts of GA3 and IAA, while the content of ABA and cytokinins was low. The inactive ZG and active iP were dominant. At the stage of cordiform thallus formation, the level of GA3 increased by 1.6, IAA by 2.4, and ABA by 1.7 times. The content of inactive iPA increased twice, significantly increased the level of active ZR and iP. At the development stage of sporophyte on the surface of gametophyte thallus, the levels of IAA, ABA, and GA3 decreased. The accumulation of inactive ZG and decrease in the content of active zeatin and zeatin riboside were documented. At all stages of gametophytes’ morphogenesis, GA3 was dominant, and its highest content was detected during the development of archegonia and antheridia. The pattern of gibberellic acid and zeatin riboside accumulation has shown the key role of these hormones in the regulation of growth processes and the development of reproductive structures of P. aculeatum gametophytes.

Cytokinins in Chick-pea Seeds Identification and Transformation during Germination and Seedling Growth

Summary Eight cytokinins were detected in germinated chick-pea ( Cicer arietinum L. var. Castellana) seeds. Treatments of extracts with β-glucosidase revealed the presence of two cytokinin glycosides: zeatin glucoside and glycosil zeatin riboside. Treatment with potassium permanganate allowed the differenciation of dihydrozeatin and dihydrozeatin riboside. These dihydro forms are present at advanced stages of germination.

Cytokinin Changes in Embryo and Endosperm of Cassia fistula during Fruit Growth

Cytokinin activity was determined in embryo and endosperm tissues from 30-day (stage 1), 55-Jay (stage 2), and 80-day (stage 3) old fruits of Cassia fistual. High cytokinin activity was associated with stage 1 and the least in stage 3. This indicated that the cytokinins disappeared during the course of seed development. Sephadex LH-20 column chromatography with 35% ethanol indicated the presence of cytokinins coeluting with zeatin glucoside, zeatin riboside, and zeatin. Qualitatively the cytokinins in the embryo and endosperm were identical at all the stages. The putative zeatin glucoside predominated at stage 1 but was absent in the later stages while only zeatin riboside was present at stage 3. The high cytokinin activity in the endosperm at early stages indicates that it may act as a supplier of cytokinins to the embryo during these periods. The possible significance of these findings is discussed.

A cytokinin complex from the developing fruits of Aegle marmelos

Following ion‐exchange, Sephadex LH‐20 and paper chromatography of the methanolic extracts of young, developing fruits of Aegle marmelos Correa, cytokinin‐like activity in the soybean callus assay was detected in six fractions. Of the four butanol‐soluble compounds, two were tentatively identified as zeatin and zeatin riboside, and the others as zeatin glucoside and zeatin riboside glucoside. The major cytokinino of the butanol‐insoluble fraction is probably zeatin nucleotide. The levels of compounds with cytokinin‐like activity were high during the early phase, and low in the subsequent period of fruit growth. The activity resembling that of cytokinin glucoside increased with maturation of the fruit. The content of free cytokinins in the fruits was more than that released from the tRNA.

Cytokinin activity in Lupinus albus

The fate of {8‐14C}zeatin injected into the mature leaves and oldest fruits of fruiting white lupin plants (Lupinus albus L.) was studied. Applied zeatin was metabolised rapidly by both organs. Within 24 h radio‐ and cytokinin‐like activity that co‐eluted with zeatin glucoside and ribosylzeatin could be detected within them. While no evidence could be found for the export of labelled cytokinins from the fruits there were some indications that zeatin glucoside may have been exported from the mature leaves.

Cytokinin activity in Lupinus albus

The distribution and metabolism of {8‐14C}zeatin incorporated into the transpiration stream of fruiting white lupin plants (Lupinus albus L.) has been studied. The distribution pattern of 14C in the different aerial organs suggests that the amount of cytokinin being incorporated into any one organ may have been a function of its transpiration rate. Once in these organs, particularly the leaves, zeatin was rapidly metabolised and or utilised. This resulted in the formation of a number of labelled compounds that did not give a response with the soybean callus bioassay. Substances co‐eluting with zeatin glucoside and ribosylzeatin appeared to be the principal biologically active metabolites. From the present evidence it can be concluded that the leaf and side shoots received a major proportion of the applied labelled cytokinin. However, the presence of a small amount of radioactivity co‐eluting with zeatin and ribosylzeatin in the fruits indicates that the high levels of cytokinins normally associated with these organs need not necessarily all have been synthesised in situ.

The Metabolism of Zeatin by Cell-free Plant Extracts

Summary Cell-free extracts prepared from senescing leaves of Ginkgo biloba and callus of Glycine max had the capacity to metabolise applied zeatin. The application of 8-[ 14 C]-zeatin to soybean callus extracts resulted in the recovery of four peaks that were active in the soybean callus bioassay. These peaks, yielding cytokinin activity, were also responsible for most of the radioactivity recorded. It would appear as if cell-free extracts are less efficient than intact cells in the conversion of zeatin to zeatin glucoside. The possibility nevertheless exists of using these techniques to obtain the enzymes that are responsible for the metabolism of zeatin in living cells.

The effect of stratification on the endogenous levels of gibberellins and cytokinins in seeds of douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) and sugar pine (Pinus lambertiana Dougl.)

Abstract Seeds of Douglas‐fir and sugar pine which had been exposed to various periods of moist chilling (stratification) were extracted and bioassayed for gibberellin and cytokinin activity. In Douglas‐fir a peak of gibberellin activity increased progressively during stratification and was seven times higher after 7 weeks, but declined subsequently. No change in the level of cytokinin activity was observed during stratification. However, a slight increase (1.7‐fold) occurred in stratified seeds placed at 22°C for 3 days.In sugar pine a high level of gibberellin activity, approximately 20‐fold higher than in unstratified controls, was present in extracts of seeds which had been stratified for 8 weeks. After 10 weeks of stratification cytokinin levels had increased approximately 200‐fold. Four cytokinin‐like substances were detected in seeds. Three of the substances are similar in their chromatographic properties to zeatin glucoside, zeatin riboside and zeatin, respectively. Both gibberellin and cytokinin activity declined rapidly after reaching maximum levels.In seeds with the coats removed, germination was rapid and complete in the absence of stratification. Prior to radicle emergence in coatless seeds cytokinin activity increased to a maximum (approximately a 1‐7‐fold increase) within 24 h. Significant levels of gibberellin‐like substances were present after 8 h. Gibberellin activity could not be detected in coatless seeds which were imbibed in AMO‐1618, and germination was inhibited significantly.

Investigations into the Possibility that Potato Buds Synthesize Cytokinins

In an attempt to determine whether potato buds synthesize cytokinins, tubers and potato pieces were subjected to conditions which both retard and accelerate bud development. Cytokinin activity was recorded in the tubers and sprouts under different experimental conditions. Most of the com pounds detected had chromatographic properties resembling those of zeatin, zeatin riboside, and zeatin glucoside. It would appear as if the buds and sprouts do not synthesize cytokinins. Initial bud growth may be dependent on the supply of cytokinins within the mother tubers, while the increase in the sprouts could be the result of root development at their basal ends.

Endogenous cytokinins in the fruits of ripening and non-ripening tomatoes

Ripening fruits of a normal strain ( Rutgers) of tomato ( Lycopersicon esculentum Mill.) were found to contain lower levels of endogenous cytokinins than fruits of a non-ripening mutant rin. The cytokinin content of both strains was high at the light green (breaker) stage and decreased as the fruits senesced. This decrease was more pronounced in the normal fruits. The non-ripening rin not only contained higher levels of the free base cytokinins, zeatin and zeatin riboside, but also high levels of zeatin glucoside, a storage cytokinin. It is suggested that the high levels of endogenous cytokinins in rin fruits are involved in delaying the ripening process.

Changes in Endogenous Cytokinin Levels in Kernels ofZea maysL. during Imbibition and Germination

In order to assess the potential role of endogenous cytokinins in the germination of Zea mays L. caryopses, cytokinin activity was determined in mature kernels and in kernels 1, 2, and 3 d after imbibition. Cytokinin activity was also recorded in the endosperm and embryo tissue of mature kernels and of kernels 3 d after imbibition to establish the localization and changes in the levels of endogenous cytokinins during imbibition and early germination. Using chromatographic, chemical, and enzymic techniques, compounds with chromatographic properties resembling those of zeatin, zeatin riboside, zeatin glucoside, zeatin riboside glucoside, and their respective dihydro derivatives were detected in extracts from mature maize kernels. From analyses of the endosperm and embryo tissue at the two stages, it appears that the cytokinin glucosides present in the endosperm are transported to the embryonic axis for utilization in growth and development of the seedling. This concept is supported by the fact that the levels of /? glucosidase activity detected were highest in the embryos, particularly in the radicles, 3 d after imbibition.

Endogenous Cytokinins and the Breaking of Dormancy and Apical Dominance in Potato Tubers

Cytokinins are present in all parts of potato tubers, and are equally distributed between the apical, lateral, and internodal tissue when dormant. However, the breaking of dormancy coincided with a rapid increase in the free base cytokinin levels in the apical buds and the tissue adjacent to it. These high levels of cytokinin in the apical tissue were maintained while apical dominance was displayed. Once apical dominance was overcome the cytokinin levels in the lateral buds and the tissue adjacent to them were similar to the levels in the apical regions. The present evidence suggests that cytokinin glucosides are transported to the meristematic regions of the tubers where they are hydrolysed to their free bases. Amounts of free bases in excess of those required for growth are apparently again converted to storage forms (particularly zeatin glucoside) in the meristematic regions of the tubers and in the sprouts.

A Comparison of the Endogenous Cytokinins in the Roots and Xylem Exudate of Nematode-resistant and Susceptible Tomato Cultivars

Non-infested roots of a tomato cultivar (Roodeplaat Premier) susceptible to root-knot nema todes contained higher levels of endogenous cytokinins than non-infested roots of a nematode resistant cultivar (Master Fl). In both cultivars nematode infestation increased the cytokinin level in the roots. Sephadex LH-20 fractionation indicated that the xylem exudate of infested susceptible plants contained zeatin and zeatin riboside. In the roots of both cultivars a third compound, which co-eluted with zeatin glucoside, was present. The activity of all three cell division-inducing compounds was higher in the roots of susceptible plants than in roots of nematode-resistant plants. The present results support the hypothesis that cytokinins may be a controlling factor in the development of giant cells.

Seasonal Changes in the Cytokinin Content of Ginkgo biloba Leaves

AbstractDuring the course of the growing season Ginkgo biloba leaves undergo both quantitative and qualitative changes in their cytokinin content. In young expanding leaves the major cytokinins cochromatograph with zeatin and zeatin riboside. In mature and aging leaves most of the cytokinin activity was due to slow moving compounds (paper chromatography) which could be hydrolysed by β‐glucosidase. After hydrolysis the active compounds co‐chromatographed with zeatin and zeatin riboside respectively. This indicates that both zeatin glucoside and zeatin riboside glucoside are present in the mature leaves. It is suggested that these glucosides are formed when the xylem transported cytokinins are metabolized (inactivated) in the leaves.

The Identification of Zeatin Glucoside from Coconut Milk

AbstractBy means of chromatographic, mass spectrometric and enzymatic techniques the major cytokinin in butanol extracts from the milk of Cocos nucifera fruits was identified as zeatin glucoside.

Cytokinin glucoside in roots of the rice plant

A “bound form” of cytokinin extracted from roots of the rice plant was purified by column and thin layer chromatography, then analysed by gas chromatography and IR spectrophotometry. Results strongly suggest that the bound cytokinin is zeatin glucoside. This bound cytokinin showed weak activity for promoting Carrot callus growth. This activity markedly increased after acid hydrolysis or rβ-glucosidase treatments.