Key words Osmotic potential
Springer Online Journal Archives 1860-2000
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Abstract This study examines water status regulation in plants of the Oleaceae family and in some other co-occurring 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.
Type of Medium: