Uptake of Cytokinins by Acer Pseudoplatanus cells: Enzymes of the Adenosine deaminase type as possible Regulators of the Cytokine Level inside the Cell

Terrine, Claude; Dorée, Marcel; Guern, J.; Hall, Ross H.

doi:10.1007/978-3-642-65406-0_63

Cited by 3 publications

(1 citation statement)

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“…Little attention has, however, been given to detailed studies of hormone uptake by the tissue in response to various external concentrations. The few papers that have appeared during the past several years on the kinetics of uptake of plant hormones are limited in scope both with regard to the kinds of tissues used and the type and particularly the concentrations of hormones (2,5,14,26,28). In many cases, only one or two concentrations per decade have been used.…”

Section: Introductionmentioning

confidence: 99%

Uptake of Benzyladenine by Tuber Slices of Jerusalem Artichoke (Helianthus tuberosus L.) over a Wide Concentration Range

Minocha

Nissen²

1982

Plant Physiol.

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Uptake of the cytokinin benzyladenine by tuber slices of Jerusalem artichoke (HeImtks Obero L) Increased with the concentration of benzylademnle In the wndium in the range 10-' to 10-molar. The kinetics of uptake could be precisely represented by four phases of a single, multipbasic isotherm. K. and V.. increased in a regular manner upon transition to higher phases. The fit to multiphasic kinetics was significantly better than the fit to cooperative kinetics or to the sum of four Independent Michaels-Menten terms.Synthetic plant hormones have been used in a variety of plant tissues to elicit various responses. It is well known that dose response curves of plant hormones are unusually wide, covering four or even six orders of magnitude (12). Under experimental conditions, the external concentrations of hormones have been varied at will (generally within the range l0-9-l0-3 M) in order to obtain an optimal response. Little attention has, however, been given to detailed studies of hormone uptake by the tissue in response to various external concentrations. The few papers that have appeared during the past several years on the kinetics of uptake of plant hormones are limited in scope both with regard to the kinds of tissues used and the type and particularly the concentrations of hormones (2,5,14,26,28). In many cases, only one or two concentrations per decade have been used. Recent studies of hormone binding proteins and their possible dual function in the transport of hormones across the plasmalemma and as sites of hormone action (6,8,18,27) make studies of the concentration dependence of hormone uptake by plant tissues of particular interest. Such studies may thus provide important information concerning the binding of hormones to plant tissues and receptors.The results reported in this article show that the uptake of BA by tuber slices of Jerusalem artichoke increases with increasing concentrations of this hormone in the medium. Furthermore, the kinetics of uptake correspond well to the multiphasic model described previously for uptake of inorganic and organic solutes ( 15,23,24). The implications of a multiphasic carrier for hormone uptake in relation to a possible mode of action of hormones are discussed briefly. A preliminary report of these findings has appeared (17). ' After appropriate periods of incubation, tissue slices were washed in running water for 15 min. Each slice was solubilized separately in 0.5 ml of BTS solubilizer (Beckman) for 3 h at 500C. Radioactivity was assayed by liquid scintillation counting.Details of the statistical analysis of uptake data have been described previously (11,22,24). RESULTSTime Course of BA Uptake. Accumulation of BA in tissue slices with time was studied at four different concentrations. In each case, 32 slices were incubated in 40 ml medium containing 0.4 ,ICi 114C]BA (0.082 /uCi for the lowest concentration). At indicated times, four slices were removed from each flask and processed as described in "Materials and Methods." The results presented in Figure...

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Section: Introductionmentioning

confidence: 99%