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See detailAre hyperhydric shoots of Prunus avium L. energy deficient?
Franck, Thierry ULg; Gaspar, Thomas ULg; Kevers, Claire ULg et al

in Plant Science (2001), 160(6), 1145-1151

The content of oxidized and reduced pyridine nucleotides and some enzymatic activities of the oxidative pentose phosphate and glycolytic pathways were compared in normal (NS, growing on agar) and ... [more ▼]

The content of oxidized and reduced pyridine nucleotides and some enzymatic activities of the oxidative pentose phosphate and glycolytic pathways were compared in normal (NS, growing on agar) and hyperhydric (HS, growing on gelrite) shoots of Prunus avium L. after 4 weeks of in vitro culture. The chlorophyll fluorescence from leaves and the redox capacity or the plasma membrane (reduction of exogenously added ferricyanide) of both types of shoots were recorded. The pool of oxidized and reduced pyridine nucleotides was lower in HS th;ln in NS. These results suggested a reduced metabolism of HS in comparison to normal ones. This hypothesis was also supported by other observations. First, chlorophyll fluorescence measurements showed a lower chlorophyll content and a slight reduction of the photosynthetic capacity in HS. Second, the low activity of some enzymes of oxidative pentose phosphate pathway (OPP) and glycolysis indicated a decline of these biochemical pathways in HS with the consequence of a reduced production of chemical energy in the form of NAD(P)H and ATP. Finally, the lower reduction of ferricyanide by I-IS suggested a lower rate of redox reactions at the level of the plasma membrane of these shoots in comparison to NS. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved. [less ▲]

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See detailIAA-oxidase activity and auxin protectors in nonrooting, rac, mutant shoots of tobacco in vitro
Faivre-Rampant, Odile; Kevers, Claire ULg; Gaspar, Thomas ULg

in Plant Science (2000), 153(1), 73-80

The peroxidase and IAA-oxidase activities, the degree of auxin protection and the amount of soluble phenolics were determined in in vitro cultured shoots of a nonrooting mutant, inc, of tobacco compared ... [more ▼]

The peroxidase and IAA-oxidase activities, the degree of auxin protection and the amount of soluble phenolics were determined in in vitro cultured shoots of a nonrooting mutant, inc, of tobacco compared to its wild homologue. The mutant and wild shoots showed similar peroxidase variations along the growth cycle of 21 days, but with higher levels of activity for the I ac mutant. During this growth cycle, the minimum of peroxidase activity occurred at day 14 for both tobacco whole shoots. However. this minimum of activity did not occur at the same day in the basal part of the stem, where roots may appear, of the two types of tobacco. Both mutant and wild whole shoots showed about the same IAA-oxidase activity in the fractions resulting from a gel filtration of the crude extracts through a sephadex G-100 column but differed in the degree of auxin protection. The rac shoots exhibited a very high level of auxin protectors of low molecular weight, among which chlorogenic acid. They were also characterized by eight to nine times higher level of soluble phenolics. The relationships between these biochemical aspects in relation to the absence of root formation in the me mutant are discussed. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved. [less ▲]

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See detailCytokinins and ethylene stimulate indole alkaloid accumulation in cell suspension cultures of Catharanthus roseus by two distinct mechanisms
Yahia, Abdelouahab; Kevers, Claire ULg; Gaspar, Thomas ULg et al

in Plant Science (1998), 133(1), 9-15

The interactions between cytokinins and ethylene on alkaloid accumulation in a periwinkle cell line have been examined. It was found that (a) either exogenously-applied cytokinins or ethylene (the latter ... [more ▼]

The interactions between cytokinins and ethylene on alkaloid accumulation in a periwinkle cell line have been examined. It was found that (a) either exogenously-applied cytokinins or ethylene (the latter through ethephon degradation) greatly enhanced ajmalicine accumulation in cells subcultured in a 2,4-dichlorophenoxyacetic acid-free medium; (b) the enhancing effect of cytokinin was not mediated by enhancement of endogenous ethylene production contrary to what is found in some plant models, (c) the responses to exogenous cytokinin and ethylene were additive and showed a different pattern of expression. It may be concluded that cytokinin and ethylene can up-regulate the alkaloid production in a periwinkle cells through independent pathways when added exogenously to the cultures. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved. [less ▲]

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See detailAuxin-polyamine interaction in the control of the rooting inductive phase of poplar shoots in vitro
Hausman, J. F.; Kevers, Claire ULg; Gaspar, T.

in Plant Science (1995), 110(1), 63-71

Changes in endogenous free IAA and its conjugate IAAaspartate as well as in endogenous polyamines were analysed in in vitro poplar shoots during their inductive phase, under the effect of the rooting ... [more ▼]

Changes in endogenous free IAA and its conjugate IAAaspartate as well as in endogenous polyamines were analysed in in vitro poplar shoots during their inductive phase, under the effect of the rooting auxin NAA, in combination or not with polyamines or inhibitors of polyamine biosynthesis. In vitro raised poplar shoots rooted 100% when treated by NAA (0.3 mg/l) for 7 h, the previously determined duration of the inductive phase. Spermidine and aminoguanidine (AG, an inhibitor of diamine oxidase) alone were unable to promote rooting under these conditions, and counteracted the NAA rooting effect. Putrescine and cyclohexylamine (CHA, an inhibitor of spermidine synthase) on the contrary did not oppose the NAA effect and promoted up to 40% rooting when applied alone. The levels of free indoleacetic acid (IAA) and of its aspartate conjugate IAAsp elevated up to peaks situated at the 7th and 8th h, respectively in the basal parts of the NAA-treated shoots. Putrescine, when added toegether with NAA, did not affect the typical IAA and IAAsp increases (except a displacement of the peaks to the 8th and 10th h, respectively); when applied alone, it provoked elevation of their levels to limited extents. Quite similar results were recorded with CHA. Spermidine and AG counteracted the NAA induced elevations of IAA and IAAsp. The level of endogenous putrescine typically increased up to a peak at the 6th h in the basal part of the NAA-treated shoots only, was slightly affected by exogenous putrescine and CHA application but significantly reduced by spermidine and AG supply. The NAA inducing rooting treatment did not affect the variation of the levels of endogenous spermidine and spermine but putrescine treatment (also spermidine to a lesser extent) led to increases of their levels. The relationships between auxin and putrescine temporary accumulation are discussed as well as the involvement of the different polyamines in the rooting inductive process. © 1995. [less ▲]

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