Phytohormone Levels of Drought‐acclimated Laurel Seedlings in Semiarid Conditions

The effect of acclimation to drought in seedlings of Mediterranean evergreen sclerophyll Laurus nobilis L. (laurel) was studied in semiarid field conditions. The phytohormones abscisic acid (ABA), gibberellic acid (GA 3), zeatin (Z) and indole-3-acetic acid (IAA) contents, plant water potential, photochemical efficiency, and morphological characters were determined. Seedlings were acclimated to drought in nursery where half of the plants were subjected to water deficit (50 % of field capacity) during 5 months. The other half was irrigated regularly at field capacity and served as controls. Then seedlings were transplanted to semiarid field conditions around Urla (Aegean Region-Turkey) while exposed to drought stress. Measurements were done ten months after transplanting. Plant water potential reached-2.5 MPa in acclimated seedlings and-1.5 MPa in non-acclimated controls. GA 3 and Z contents of leaves were higher in acclimated seedlings as compared to control ones, while ABA was not changed. On the contrary, IAA content of the leaves of acclimated seedlings was reduced. The photochemical efficiency of PSII in acclimated seedlings was maintained at a higher level than in controls, while leaf area and plant height were 204 Yildiz Aktas et al.