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1.
The stability of [3H]zeatin riboside supplied to freshly excised tobacco pith explants was found to be inversely related to -naphthaleneacetic acid concentration in the incubation medium. At higher concentrations of -naphthaleneacetic acid greater breakdown of [3H]zeatin riboside was indicated by higher levels of degradative metabolites (adenine, adenosine and adenosine nucleotides) formed. This auxin effect on cytokinin metabolism appears to be mediated, at least in part, through cytokinin oxidase. The results of in-vitro assays carried out with partially purified enzyme from corn kernels substantiale this conclusion. These findings are discussed in relation to recent observations of auxin and cytokinin levels in crown-gall tumours with altered morphology.Abbreviations FPLC
fast protein liquid chromatography
- HPLC
high-performance liquid chromatography
- IP
isopentenyladenine
- NAA
naphthaleneacetic acid
- ZR
zeatin riboside 相似文献
2.
Irrespective of their age, leaves of Ginkgo biloba metabolised applied 8 (14C) zeatin to compounds of similar chromatographic properties. Glucosylation is apparently not a normal feature of cytokinin metabolism in immature leaves. However, the application of zeatin to these leaves did result in the formation of metabolites which co-chromatographed with glucosylated cytokinins. As far as cytokinin metabolism is concerned therefore, this application of excess zeatin allowed immature leaves to behave as mature or senescing leaves. Overall metabolism was fastest in immature leaves. From the metabolites formed it would appear as if oxidation, which resulted in the formation of a metabolite which co-eluted with N-(purin-6-yl)glycine, was also important in immature leaves. In senescing leaves glucosylation was the major form of metabolism. Extraction and re-application of the polar metabolites (formed from zeatin) to mature leaves resulted in the formation of compounds which co-chromatographed with zeatin. This suggests that these compounds could serve as precursors for zeatin or could be hydrolysed to form zeatin.Very little of the applied radioactivity was exported from the leaves irrespective of their physiological age. When the metabolites, obtained after zeatin application to mature leaves, were extracted and reapplied to the leaves, export of radioactive material was much improved. The results suggest that should cytokinins such as zeatin be translocated to mature leaves of this deciduous gymnosperm their export from the leaves would be unlikely unless first metabolised. In all probability the metabolites concerned are cytokinin glucosides.The financial support of the C.S.I.R., Pretoria, is gratefully acknowledged. 相似文献
3.
6-(2,3,4-Trihydroxy-3-methylbutylamino) purine, trivial name trihydroxy-zeatin (THZ), an oxidation product of zeatin was applied via the epidermis or cut end of Avena leaf segments. THZ did not retard senescence of the segments in either case. With epidermal application THZ remained unmetabolised while the cut end method of application resulted in its metabolism to more polar THZ metabolites of unknown identity. The Avena leaf tissue did not apparently cleave the isoprenoid side chain of the THZ molecule. 相似文献
4.
Levels of isopentenyladenosine and zeatin riboside were monitored in buds and needles of Scots pine ( Pinus sylvestris L.) seedlings grown under controlled climatic conditions and in field-grown trees. Extracts were purified by immunoaffinity chromatography and high-performance liquid chromatography. Cytokinin levels were quantified with an enzyme-linked immunosorbent assay. The cytokinin content was low in buds and needles of dormant seedlings but increased during dormancy release, reaching peak values in buds just before resumption of shoot growth. Samples collected in the field also showed a marked increase in the levels of cytokinins just prior to bud burst. Further, the biological activity of applied cytokinins in activating the dormant buds of Scots pine is shown. The results indicate a probable role of cytokinins in seedlings during dormancy release. 相似文献
5.
Effect of zeatin on the growth and indolyl-3-acetic acid and abscisic acid levels in maize roots 总被引:1,自引:0,他引:1
Elongation, indolyl-3-acetic acid (IAA) and abscisic acid (ABA) levels, – gas chromatography-mass spectrometry quantification –, in the elongating zone were analysed for maize ( Zea mays L., Cv. LG11) roots immersed in buffer solution with or without zeatin (Z). The effect of Z depends on the initial extension rate of roots. The slower growing roots are more strongly inhibited by Z (10−7 −10−5 M ) and they show a greater increase in IAA and ABA content. When compared to the rapidly growing roots, the larger reactivity of the 'slow'ones cannot be attributed to a higher Z uptake as shown when using [14 C]-Z. It is suggested that Z could regulate root elongation by acting on the IAA and/or ABA level. The comparative action of these two hormones is discussed. 相似文献
6.
David H. Lewis Garry K. Burge David M. Schmierer Paula E. Jameson 《Physiologia plantarum》1996,98(1):179-186
The cytokinin content in fruit tissue of the kiwifruit ( Actinidia deliciosa [A. Chev.] C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward) was monitored during fruit development to identify which cytokinins were present and if they were linked with specific stages of fruit growth. Cytokinins were isolated and purified by column chromatography and high-performance liquid chromatography and quantified by radioimmunoassay. A novel HPLC step utilising an amine column was successfully introduced as a preparative step in the separation of the O - and 9-glucosides from the free bases and ribosides. The radioimmunoassay results were validated, and the different cytokinins identified, by gas chromatography-mass spectrometry. Cytokinins detected in fruit included the cytokinin free bases, zeatin and isopentenyladenine, their ribosides, nucleotides and both O - and 9-glucosides. Both qualitative and quantitative changes of the cytokinins occurred during fruit development. A decrease in cytokinin concentration occurred after anthesis (from 342 pmol g−1 fresh weight at anthesis to 41 pmol g−1 fresh weight 27 days after anthesis). A large increase in cytokinin concentration and content per fruit occurred as the fruit reached commercial maturity (to 1900 pmol g−1 fresh weight). Individual cytokinins showed quite different patterns. Zeatin, in particular, showed a peak in concentration (13 pmol g−1 fresh weight) 11 days after anthesis that correlated with the beginning of the cell division phase of fruit growth. The accumulation of cytokinin (mostly zeatin riboside or zeatin nucleotide) in mature fruit may be of significance for the postharvest storage of kiwifruit fruit. 相似文献
7.
几种细胞分裂素诱导石竹外植体直接再分化成花芽的机理 总被引:4,自引:0,他引:4
用MS+2,4-D0.1mg/L为基本培养基,分别附加不同浓度的ZT、BA和KT,对石竹的叶片、茎和花等外植体直接再分化成花芽的试验表明:叶片的外植体在有BA时可再分化出只有红色花瓣的不正常花芽;在含ZT的培养基中再分化出具有1~2片叶或无叶的花芽,其花有两性花,雌花和仅单个雌蕊的不正常花,两性花可发育成结籽的果实;KT未能诱导花芽分化。茎外植体,3种CTK都不能诱导出花芽。花等外植体仅在KT3mg/L的培养中再分化出无叶的不正常花芽,ZT和BA的处理均不能诱导出花芽。 相似文献
8.
9.
Isabelle Goebel-Tourand Marie-Claude Mauro Lucienne Sossountzov Emile Miginiac Alain Deloire 《Plant Cell, Tissue and Organ Culture》1993,33(1):91-103
In an effort to understand the causes of arrest of somatic embryo development, generally observed in grapevine (Vitis sp.), histological studies were undertaken, using two cultivars (CH76 and 41B) which differ in their ability to develop into plants. Embryos with a high conversion rate (70%; CH76) formed a well-structured and functional shoot apex between two thread-like cotyledons. In contrast, embryos with a low conversion rate (10%; 41B) formed a normal root apex but lacked a well-structured shoot apex and developed a wide range of aberrant forms in the intercotyledonary area: uncontrolled cellular proliferation, formation of adventitious buds, over-growth of cotyledonary or leaf meristems. ABA increased the conversion rate of 41B embryos from 10% to 20%, but failed to improve embryo morphology. Zeatin and BAP promoted growth of 41B somatic embryos, but generated a high level of abnormalities and failed to improve conversion rate. Applied in combination with ABA, these PGRs increased the frequency of cotyledonary embryos, but decreased the conversion rate. 相似文献
10.