Involvement of malate and mannitol in the diurnal regulation of the water status in members of Oleaceae

Abstract

AbstractmThis study examines water status regulation in plants of the Oleaceae family and in some other cooccurring species that are exposed to high solar radiation, in the same habitat. Fraxinus excelsior L., one of the most studied Oleaceae in this field exhibited, during the growing season, a close relationship between diurnal variations in leaf water potential and changes in malate, mannitol and K + levels, depending on the weather conditions. On sunny days, similar variations can be observed in leaves of the other Oleaceae, with a concomitant decrease in the osmotic potential between predawn and solar noon. Malate, mannitol and the well-known osmoticum K + , contribute greatly to the osmotic potential decrease. This mechanism, which can be related to the osmotic adjustment described for both drought and salt-affected plants, appears as a general response in plants of the Oleaceae family. Among the other co-occurring species investigated, only Quercus robur L. displayed a similar mechanism under the same environmental conditions, but two other organic compounds, quinic and shikimic acids, are presumably involved. Alnus glutinosa (L.) Gaertn. and Robinia pseudacacia L. responded to a vapor deficit by partial stomatal closure, as transpiration progressed through the morning.

Changes in water status and osmolyte contents in leaves and roots of olive plants (Olea europaea L.) subjected to water deficit

“…found in leaves of CP (Fig. 4) are in accordance with those found by Peltier et al (1997) in six species of Oleaceae. In olive leaves, water deficit did not determine changes in the levels of Na ?…”

Annual changes in the concentration of minerals and organic compounds of Quercus suber leaves

“…In the gymnosperm Picea abies, quinic acid is intensively produced in the needles in spring and metabolized in summer, apparently participating in lignification processes (Dittrich and Kandler 1971 in Leuschner et al 1995). The presence of quinic acid in Q. suber has already been reported (Boudet 1973), but our results show a pattern of distribution during the year quite distinct from that described for Q. robur (Peltier et al 1998). Most striking is the close parallelism which exists between quinic acid concentration in Q. suber leaves and the insolation and temperature data.…”

“…For instance, during the growing season of Fraxinus excelsior, a close relationship between diurnal variations in leaf water potential and changes in malate, mannitol and K þ levels was observed (Peltier et al 1998). In Quercus robur, a similar importance was attributed to malate, although in this species, quinic and shikimic acids were reported to be also involved in osmotic balancing (Peltier et al 1998). What seems peculiar in the Q. suber leaves is the predominance of quinic acid and the low levels of malic acid, which reached the highest concentration in young leaves, but decreased during the most stressful period (June to September) and increased (together with citric acid) in autumn/ winter when the concentration of quinic acid was low.…”

“…For instance, during the growing season of Fraxinus excelsior, a close relationship between diurnal variations in leaf water potential and changes in malate, mannitol and K þ levels was observed (Peltier et al 1998). In Quercus robur, a similar importance was attributed to malate, although in this species, quinic and shikimic acids were reported to be also involved in osmotic balancing (Peltier et al 1998).…”

Success in the demographic expansion of Fraxinus excelsior L.

“…Ψ t (s s s), Ψ p (w w w) and Ψ w (q q q) were determined after graphical analysis of P-V curves. ε ε is given by the slope of the curve showing the variations of Ψ t (from Peltier and Marigo 1999) involved in the regulation of water status but here, at a diurnal level Peltier et al 1997). Field measurements of diurnal changes in Ψ w and malate and mannitol levels were carried out in spring and summer for expanded leaves.…”