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sur le développement des zones arides et semi-arides

Titre : Different strategies for water availability in four Mediterranean sclerophyllous plants (Ceratonia siligua, Olea oleaster, Pistacia terebinthus and Quercus coccifera)

Sağlıklı ve bozulmuş alanlarda yetişen bazı Akdeniz sklerofil türlerin (Ceratonia siliqua, Olea oleaster, Pistacia terebinthus, and Quercus coccifera) su alımında uyguladıkları değişik stratejileri

Auteur : SAKÇALI Serdal

Université de soutenance : Fatih Üniversitesi

Grade : Master of Science (MSc) in Biology 2000

Résumé
Quercus coccifera, Ceratonia siliqua, Pistacia terebinthus, Olea oleaster, drought resistance, sclerophylly, water relations, impact of water deficit stress. Diurnal time course of the water relations of four sclerophylls has been studied on Healthy and Degraded sites with the aim of : a) discriminating drought resistant from vulnerable species ; b) selecting the species more suitable for reforestation and/or cultivation ; c) getting a suitable parameter describing the water stress impact on vegetation as a tool for assessing the ongoing trends. Out of the species used C. siliqua, showed high maximum gL’s with high RWC’s under field conditions, and relatively constant ^mm and %d’s. This suggests that this plant lost consistent amounts of water (high gL) that were dynamically recovered (high RWC) even in the warmest hours of the day. As a consequence, this species can be considered as a suitable candidate to natural reforestation of degraded areas of the Mediterranean Basin region. Moreover, C. siliqua is a species of increasing economic interest for industrial use of seeds and fruits. O. oleaster plants appeared to be unable to prevent dehydration in spite of consistent decrease of gL, when subjected to increasing water stress. Stomatal closure in fact, was not sufficient to prevent water loss and RWC dropped to about 70 %.Although O. oleaster proved to be sensitive to aridity, wild olive species was a suitable indicator of the degree of degradation of the different areas under study and hence, it could be conveniently used as a "field biomonitor". P. terebinthus species is water spender. Under water shortage condition inspite of complete closure of stomata (gL dropped to 0.08 scm" ), RWC showed variable values. Under these circumstances these plants can not sustain longer under hard conditions. Adaptive strategy of Q. coccifera is dessication postponer based on water saving. When growing in healthy site it typically shows high gL activity and also high RWC (average 83%). But in degraded site, this species reduced gL, thus maintaining high RWC’s (over 80 %) and preventing ^Fl to drop to critical values. Our studies clearly enlighten the fact that the integral of diurnal Mt’l changes is a useful method to assess the impact of water stress on plants, and trends towards desertification.

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