Intra- and inter-cultivar impacts of salinity stress on leaf photosynthetic performance, carbohydrates and nutrient content of nine indigenous Greek olive cultivars

Nine indigenous Greek olive cultivars (‘Aetonicholia Kynourias’, ‘Arvanitolia Serron’, ‘Ntopia Atsicholou’, ‘Koroneiki’, ‘Lefkolia Serron’, ‘Ntopia Pierias’, ‘Petrolia Serron’, ‘Smertolia’ and ‘Chryssophylli’) were evaluated for their tolerance to salinity stress (four levels of sodium chloride salt, i.e., 0, 50, 100 and 200 mM) under hydroponic conditions. Their photosynthetic performance, leaf carbohydrates (mannitol, glucose, fructose and sucrose) and nutrients (nitrogen, potassium, calcium, sodium and chloride) were assessed. Photosynthetic performance was reduced under salt stress and this was mostly evident in ‘Koroneiki’ and ‘Ntopia Atsicholou’ (approximately 20% of the corresponding controls), while ‘Ntopia Pierias’, ‘Smertolia’ and ‘Petrolia Serron’ did not exhibit significant changes with salinity level. Photosynthesis (A) was reduced mainly due to severe stomatal limitations. A weak correlation was detected between A and intercellular CO2 (Ci) indicating a minor role of non-stomatal limitations. Carbohydrates in the leaves did not seem to undergo significant changes. Mannitol accumulated in ‘Chryssophylli’ leaves and glucose in ‘Arvanitolia Serron’ leaves under the highest salinity level. Potassium concentration per leaf water volume was significantly reduced (especially under the highest salinity level −45 to 60% of control). Calcium was not significantly affected although Ca/Na ratio was reduced, due to the great increase of sodium concentration. ‘Lefkolia Serron’ and ‘Arvanitolia Serron’ accumulated the least sodium in their leaves, exhibiting high K/Na ratio under the highest salinity level, indicating a better regulation of potassium influx under high sodium concentration. Based on the present data and on previous research ‘Lefkolia Serron’ and ‘Arvanitolia Serron’ are the two cultivars with the highest tolerance against salinity stress.