Effects of Irrigation Water Fluoride on Relative Water Content, Photosynthetic Activity, and Proline Accumulation in Young Olive Trees (olea Europaea L. Cv Chemlali) in Arid Zones

The effects of increasing the NaF concentration supplied through the irrigation water on some photosynthetic and physiological features of young olive trees grown under the ambient environmental conditions of an arid climate in Sfax, Tunisia, were investigated. Thirty-six uniform one-year-old self-rooted olive trees (Olea europaea L. cv Chemlali) were transplanted into 5 L pots and irrigated for 5 months with NaF concentrations of 0 (control), 20, 40, and 80 mM NaF. The responses of the young olive trees grown under fluoride stress were slight reductions of leaf relative water content, net photosynthesis, stomatal conductance, transpiration rate, photosynthetic pigment content, and growth traits. Interestingly, the Chemlali olive tree was relatively resistant to the fluoride stress under the experimental conditions since it maintained some photosynthetic activity and a suitable leaf relative water content. Moreover, the positive evolution in the content of proline and soluble sugars with increasing NaF stress was further evidence of the effect of these osmoticums for improving the tolerance of the Chemlali olive trees to fluoride stress.