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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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