Are hyperhydric shoots of Prunus avium L. energy deficient?

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 g elrite) shoots of Prunus avium L. after 4 weeks of in vitro culture. The ch lorophyll fluorescence from leaves and the redox capacity or the plasma mem brane (reduction of exogenously added ferricyanide) of both types of shoots were recorded. The pool of oxidized and reduced pyridine nucleotides was l ower 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 o bservations. First, chlorophyll fluorescence measurements showed a lower ch lorophyll 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 path ways 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 ferricyanid e by I-IS suggested a lower rate of redox reactions at the level of the pla sma membrane of these shoots in comparison to NS. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.