Institution: | aInstitut National Agronomique de Tunisie, 43 Avenue Charlnicol, 1082 cité El Mahrajen, Tunisie, Tunisia bInstitut de l’Olivier de Sousse, 40 Rue Ibn Khouldoun, 4061 Sousse, Tunisia |
Abstract: | The effect of water deprivation on plant water status, photosynthetic gas exchange and fluorescence parameters in two different olive tree varieties (Olea europaea L. var. ‘koroneiki’, ‘Meski’) was studied. Two-year-old olive trees, grown in pots in greenhouse, were subjected to one of three drought treatments (i.e., mild, moderate and severe drought stress) and compared to control trees. Both the leaf water potential (Ψw) and the relative water content (RWC) of the two varieties decreased with increasing levels of drought stress. Koroneiki showed higher (less negative) values of Ψw and lower values of RWC than the Meski, particularly during severe drought stress. Net photosynthetic assimilation and stomatal conductance declined with drought. This inactivation of photosynthetic activity was accompanied by changes in the fluorescence characteristics. The PSII maximal photochemical efficiency (Fv/Fm), the intrinsic efficiency of open PSII reaction centres (Fv′/Fm′), the photochemical efficiency of PSII (ΦPSII) and the total electron flow (Jt) decreased during the development of drought stress. The non-quenching photochimique (qN) showed an increase in the response to water deficit. These observations are discussed in relation to the strategies developed to grow drought-resistant olive trees in arid areas. |