Increasing salt tolerance in Olive, Olea europaea L. plants by supplemental potassium nutrition involves changes in ion accumulation and anatomical attributes

The effects of supplemental potassium were studied on growth, ion concentration and anatomical parameters in one year old olive trees, Olea europaea L., grown in sand culture in greenhouse at different levels of NaCl for 80 days. The experiments were conducted in a completely randomized design as a factorial. Factor one was salinity (0, 40 or 80 mM NaCl) and the second factor was potassium levels of 4 and 8 mM. Salinity caused a significant decrease in the growth of plants; however, the supplemental potassium could partly ameliorate the adverse effects of salinity on growth. Due to salinity Na+ and Cl- ions accumulated and the K+ /Na+ ratio decreased in the plants. The lower relative water content and the higher cortex /stele ratio in plants under salinity indicate water deficit. Under salinity, however, the supplemental potassium led to lower Na+ and higher K+ and P concentration which probably reduced the toxicity. The ratio of cortex to stele became normal as salt-grown plants were supplemented with potassium. Supplemental potassium increased palisade cell layer thickness in leaves under salinity that may be accompanied with increased potential for photosynthesis. The results indicate that supplemental potassium can be useful in ameliorating salinity stress effects in olive plants.