Plant Science 160 (2001) 1145 – 1151 Are hyperhydric shoots of Prunus aium L. energy deficient? T. Franck a, *, T. Gaspar b , C. Kevers b , C. Penel c , J. Dommes b , J.F. Hausman a a Centre de Recherche Public -Gabriel Lippmann, CREBS, Aenue de la Faı ¨encerie, 162a, L-1511 Luxembourg, Luxembourg b Biologie Mole ´culaire et Hormonologie Ve ´ge ´tales, Institut de Botanique B22, Uniersite ´ de Lie `ge -Sart Tilman, B-4000 Lie `ge, Belgium c Laboratoire de Biochimie et de Physiologie Ve ´ge ´tales, Uniersite ´ de Gene ` e, Unibastion, 4 Place de l’Uniersite ´ , CH-1211 Gene ` e, Switzerland Received 04 December 2000; received in revised form 22 January 2001; accepted 29 January 2001 Abstract 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 aium L. after 4 weeks of in vitro culture. The chlorophyll fluorescence from leaves and the redox capacity of 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 than 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 HS suggested a lower rate of redox reactions at the level of the plasma membrane of these shoots in comparison to NS. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Chlorophyll fluorescence; Glycolysis; Oxidative pentose phosphate pathway; Hyperhydricity; NAD(P)H and NADH; Prunus aium L. www.elsevier.com/locate/plantsci 1. Introduction During tissue culture, plants are exposed to a wide range of stressing conditions. Among them are injuries caused during explantation, high os- moticity of the culture medium (high sucrose and ammonium contents), high relative humidity and gas accumulation in the atmosphere of the jar, unusual hormonal treatment (high cytokinin appli- cation), … [1,2]. Although most plants can adapt to these environmental conditions, some of them become abnormal with a translucent aspect gener- ally due to a chlorophyll deficiency and higher water content mostly located in the intercellular spaces [3]. This phenomenon is called vitrification or hyperhydricity [4]. Under precise conditions, hyperhydricity can irreversibly evolve towards a loss of regenerative ability of the tissue [5]. Hyperhydricity of Prunus aium L. shoots has been reported to be induced and expressed in vitro by a 4 weeks multiplication cycle merely by replac- ing agar by gelrite [6]. After such a treatment, this material showed typical symptoms of hyperhydric- ity: translucent stems and leaves, wrinkled and curled leaves [6]. Biochemical studies showed that these abnormal plantlets (HS) had a higher water content and a lower chlorophyll content than the normal ones (NS). Cytological observations indi- cated less chloroplasts in HS than in NS [6]. In most plants subjected to stress, a general increase of the enzymatic systems that eliminate H 2 O 2 (peroxidases, catalase and the ascorbate – glutathione cycle) is observed [7]. In HS, a lower Abbreiations: HS, hyperhydric shoots; NS, normal shoots; OPP, oxidative pentose phosphate pathway. * Corresponding author. Tel.: +352-47-0261438; fax: +352-47- 0261389. E-mail address: franck@crpgl.lu (T. Franck). 0168-9452/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII:S0168-9452(01)00362-4