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.

Micropropagation of a local olive cultivar for germplasm preservation

Abstract: In vitro shoot culture was applied to an Italian local cultivar Nebbiara of olive (Olea europaea L.) to preserve its endangered germplasm. This cultivar showed a notable difficulty for the in vitro establishment due to heavy pathogen contamination. Mercury chloride and sodium hypochloride in the sterilisation step and antibiotics in culture media allowed to overcome the problem. Proliferation of shoot apical bud on olive culture medium with 36 g dm−3 mannitol and 4.56 μM zeatin appeared very satisfactory. All the explants tested rooted during a subculture (1 month) preceeded by a 5-d long dark pre-treatment.

Cytokinin oxidase from auxin- and cytokinin-dependent callus cultures of tobacco (Nicotiana tabacum L.)

Abstract: Cytokinin oxidase was extracted and partially purified from auxin- and cytokinin-dependent callus tissue of tobacco (Nicotiana tabacum L. cv. Wisconsin 38). The activity of the enzyme preparation was examined using an assay based on the conversion of tritiated N6-(Δ2-isopentenyl)adenine ([2,8-3H]iP) to adenine. Cytokinin oxidase exhibited a temperature optimum at 45–50°C and a relatively high pH optimum (8.5–9.0). The apparent Km value of the enzyme was 4.3 μM for iP. On the basis of the substrate competition assays, iP was determined to be the preferred substrate of the enzyme. Substrate competition was also observed with zeatin and the cytokinin-active urea derivative Thidiazuron. Cytokinins bearing saturated isoprenoid side chains or cyclic side chain structures, as well as auxins and abscisic acid, had no effect on the conversion of [2,8-3H]iP. The cytokinin oxidase exhibited increased activity in the presence of copper-imidazole complex in the reaction mixture. Under optimal concentrations of copper (15 mM CuCl2) and imidazole (100 mM), the enzyme activity was enhanced ca. 40-fold. Under these conditions the pH optimum was lowered to pH 6.0, whereas the temperature optimum, the apparent Km value, and the substrate specificity were not altered. Most of the enzyme moiety did not bind to the lectin concanavalin A. The characteristics of cytokinin oxidase presented here suggest that a novel molecular form of the enzyme, previously identified and characterized in Phaseolus lunatus callus cultures (Kaminek and Armstrong (1990) Plant Physiol 93:1530), also occurs in cultured tobacco tissue.

Effects of exogenous hormones on floret development and grain setin wheat

Abstract: At specific stages during floret development, solutions of IAA,GA3, zeatin and ABA were injected into the leaf sheath around theyoung spike of wheat (Triticum aestivum L.) to study theregulating effects of exogenous hormones on floret development. Zeatin promotedfloret development and significantly increased the number of fertile florets aswell as grain set, especially at the stage of anther-lobe formation. Zeatinalsoincreased the sugar concentrations in spikes at anthesis. In contrast, IAA,GA3 and ABA inhibited floret development, with different patternsforeach of the hormones. IAA inhibited the development of the whole spike and allflorets in the spikelets such that grain loss occurred in all positions in thespikelets. GA3 increased the number of fertile florets per spike,butdecreased grain set of the third floret in each spikelet, especially whenapplied at terminal spikelet formation. ABA inhibited floret development, anddecreased the number of fertile florets and grain set at almost all developmentstages, except at anther-lobe formation. The inhibitory effect of ABA wasmainlyon the first and third florets in each spikelet.