Two years old self-rooted Koroneiki olive trees (Olea europaea L.) were subjected to two irrigation regimes,
i.e. the fully irrigated and the severely water stressed trees, while they were treated with three alleviating products of different mode of action. The products used were the osmolyte glycine betaine, the
antioxidant Ambiol and the heat and irradiance reflecting kaolin clay particles. The effects of product
application and water regime on leaf characteristics, shoot and root growth, photosynthesis, leaf compatible solids (carbohydrates) concentration and yield were evaluated. All products applied, exhibited
significant alleviating action, based on the relative alleviation index. Irrigated trees exhibited greater
growth than drought stressed ones, while the ameliorating products maintained the water content of
the leaves under drought conditions and resulted in lower leaf tissue density. On the other hand carbon
assimilation rate, stomatal conductance and intrinsic water use efficiency were significantly reduced
under drought stress, while the opposite stood for intercellular CO2. Drought stress resulted in elevated
sucrose leaf concentration, while the application of Ambiol increased stachyose concentration and that
of glycine betaine did the same with the mannitol concentration. Among the alleviating products tested
in this experiment Ambiol and glycine betaine had a significant positive effect on leaf water content,
photosynthesis and yield under both drought and well irrigated conditions.