Eco-physiological behaviour of some mediterranean plants as suitable candidates for reclamation of degraded areas

Diurnal time course of the water relations of Ceratonia siliqua, Quercus coccifera, Pistacia terebinthus and Olea oleaster was studied on healthy and degraded sites for getting a suitable parameter describing the water stress impact on vegetation, and selecting the species suitable for reforestation. Out of the species used C. siliqua, showed high maximum stomatal conductance (g(L)), with high relative water content (RWC) under field conditions, and relatively constant minimum (midday) water potential (Psi(min)) and pre-dawn water potential (Psi(pd)'s). O. oleaster plants appeared to be unable to prevent dehydration inspite of consistent decrease of stomatal conductance (g(L)), when subjected to increasing water stress. Stomatal closure in fact, was not sufficient to prevent water loss and relative water content (RWC) dropped to about 70%. P. terebinthus species is water spender. Under water shortage condition inspite of complete closure of stomata (stomatal conductance dropped to 0.08 s cm(-1)), relative water content showed variable values. Q. coccifera typically showed high stomatal conductance activity and also high relative water content (average 83%) on healthy site, but on the degraded site it reduced, stomatal conductance, thus maintaining high RWCs (over 80%) and preventing leaf water potential (Psi(L)) to drop to critical values. (C) 2003 Elsevier Ltd. All rights reserved.