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Zeatin

About: Zeatin is a research topic. Over the lifetime, 2467 publications have been published within this topic receiving 64092 citations. The topic is also known as: Zeatin & (E/Z)-zeatin.


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Journal ArticleDOI
TL;DR: Interactions between cytokinin metabolism, Rubisco and protein levels, photosynthesis and plant nitrogen partitioning were studied in transgenic tobacco plants showing delayed leaf senescence through a novel type of enhanced cytokinIn synthesis, targeted to senescing leaves and negatively auto-regulated (PSAG12‐IPT), thus preventing developmental abnormalities.
Abstract: We studied the impact of delayed leaf senescence on the functioning of plants growing under conditions of nitrogen remobilization. Interactions between cytokinin metabolism, Rubisco and protein levels, photosynthesis and plant nitrogen partitioning were studied in transgenic tobacco (Nicotiana tabacum L.) plants showing delayed leaf senescence through a novel type of enhanced cytokinin synthesis, i.e. targeted to senescing leaves and negatively auto-regulated (PSAG12‐IPT), thus preventing developmental abnormalities. Plants were grown with growthlimiting nitrogen supply. Compared to the wild-type, endogenous levels of free zeatin (Z)- and Z riboside (ZR)type cytokinins were increased up to 15-fold (total ZR up to 100-fold) in senescing leaves, and twofold in younger leaves of PSAG12‐IPT. In these plants, the senescenceassociated declines in N, protein and Rubisco levels and photosynthesis rates were delayed. Senescing leaves accumulated more ( 15 N-labelled) N than younger leaves, associated with reduced shoot N accumulation (‐60%) and a partially inverted canopy N profile in PSAG12‐IPT plants. While root N accumulation was not affected, N translocation to non-senescing leaves was progressively reduced. We discuss potential consequences of these modified sink‐source relations, associated with delayed leaf senescence, for plant productivity and the efficiency of utilization of light and minerals.

174 citations

Journal ArticleDOI
TL;DR: The results showed that Pb and Zn significantly delayed and impeded the germination of chickpea seeds and the negative effect of Pb on germination was higher than that of Zn.
Abstract: The present work describes the changes that take place in phytohormone contents in germinating chickpea (Cicer arietinum cv. Aziziye-94) seeds in response to heavy metal stress. For this aim, endogenous abscisic acid (ABA), gibberellic acid (GA3), zeatin (Z) and zeatin riboside (ZR) contents were followed for 24, 48 and 72 h in chickpea seeds germinating at the concentrations of 0.1, 1.0 and 5.0 mM Pb or 0.1, 1.0 and 10 mM Zn. The results showed that Pb and Zn significantly delayed and impeded the germination of chickpea seeds. The negative effect of Pb on germination was higher than that of Zn. Further, Pb increased ABA and Z contents while decreased GA3 content in the germinating seeds. The high concentrations of Zn (1.0 and 10 mM) decreased contents of Z, ZR and GA3 while 0.1 mM Zn increased the content of the same hormones. The ABA content was enhanced by Zn in all concentrations used.

172 citations

Journal ArticleDOI
TL;DR: Xylem sap contained considerable amounts of bound ABA, the level of which increased during total root drying and decreased again after rewatering, and level of cytokinins, zeatin (t-Z)+zeatin riboside ( t-ZR) and isopentenyladenine (2iP) + isopENTenyladenosine ( 2iPA), on the contrary, decreased duringRoot drying and increased again afterRewatering.
Abstract: Seedlings of rice cv. IR 36 were grown in soil in small pots with a horizontally divided root system: after 6-7 weeks, about 20% of the entire root system had protruded through the holes at the base of the pots and was kept in contact with nutrient solution. At this stage the plants were exposed to three different treatments: (a) the soil was kept watered and the protruding free roots were dried in air; (b) the free roots were kept moist and the soil left unwatered; (c) both soil and protruding roots were left unwatered for 30 h and then rewatered. During the first hours of treatment a and b, a decline in stomatal conductance was observed, whereas the stem water potential remained unchanged. The concentration of abscisic acid (ABA) in the xylem, however, increased. At later stages of treatment a and b, the stem water potential began to decrease with a parallel further increase of xylem ABA. Xylem sap contained considerable amounts of bound ABA, the level of which increased during total root drying and decreased again after rewatering. Level of cytokinins, zeatin (t-Z)+zeatin riboside (t-ZR) and isopentenyladenine (2iP) + isopentenyladenosine (2iPA), on the contrary, decreased during root drying and increased again after rewatering. The results are discussed with regard to a possible function of ABA and cytokinins as root-to-shoot signals.

172 citations

Journal ArticleDOI
TL;DR: Cytokinin nucleotides, considered as resistant to CKX attack until now, were found to be potent substrates for some of the CKX isoforms and biochemical characterization of the AtCKX1, AtCkX2, At cKX4 and AtcKX7 enzymes showed pH-dependent activity profiles.
Abstract: Transgenic tobacco plants overexpressing single Arabidopsis thaliana cytokinin dehydrogenase (CKX, EC 1.5.99.12) genes AtCKX1, AtCKX2, AtCKX3, AtCKX4, AtCKX5, AtCKX6, and AtCKX7 under the control of a constitutive 35S promoter were tested for CKX-enzymatic activity with varying pH, electron acceptors, and substrates. This comparative analysis showed that out of these, only AtCKX2 and AtCKX4 were highly active enzymes in reaction with isoprenoid cytokinins (N 6 -(2-isopentenyl)adenine (iP), zeatin (Z)) and their ribosides using the artificial electron acceptors 2,6-dichlorophenol indophenol (DCPIP) or 2,3-dimethoxy-5-methyl-1,4-benzoquinone (Q0). Turnover rates of these cytokinins by four other AtCKX isoforms (AtCKX1, AtCKX3, AtCKX5, and AtCKX7) were substantially lower, whereas activity of AtCKX6 was almost undetectable. The isoenzymes AtCKX1 and AtCKX7 showed significant preference for cytokinin glycosides, especially N 6 -(2-isopentenyl)adenine 9-glucoside, under weakly acidic conditions. All enzymes preferentially cleave isoprenoid cytokinins in the presence of an electron acceptor, but aromatic cytokinins are not resistant and are degraded with lower reaction rates as well. Cytokinin nucleotides, considered as resistant to CKX attack until now, were found to be potent substrates for some of the CKX isoforms. Substrate specificity of AtCKXs is discussed in this study with respect to the structure of the CKX active site. Further biochemical characterization of the AtCKX1, AtCKX2, AtCKX4 and AtCKX7 enzymes showed pH-dependent activity profiles.

169 citations

Journal ArticleDOI
TL;DR: Findings show that the bacteria used in this study synthesized the plant growth regulators, auxin, gibberellin, cytokinin and abscisic acid.
Abstract: In this study, auxin (indole-3-acetic acid), gibberellin, cytokinin (zeatin) and abscisic acid production were investigated in the culture medium of the bacteria Proteus mirabilis, P. vulgaris, Klebsiella pneumoniae, Bacillus megaterium, B. cereus, Escherichia coli. To determine the levels of these plant growth regulators, high performance liquid chromatography (HPLC) technique was used. Our findings show that the bacteria used in this study synthesized the plant growth regulators, auxin, gibberellin, cytokinin and abscisic acid.

168 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202333
2022103
202135
202034
201932
201848