Salinity and olive: Growth, salt tolerance, photosynthesis and yield

Olive (Olea europaea L.) is a major tree crop in the Mediterranean region and is moderately salt tolerant. Recent studies suggest that olives can be irrigated with water containing 3200 mg/l of salt (ECw of 5 dS/m) producing new growth at leaf Na levels of 0.4-0.5% d.w. Salt tolerance in olives appears to be cultivar-dependent and is likely due to control of net salt import to the shoot. The mechanism is located within the roots and prevents salt translocation, rather than salt absorption. It is probably that K-Na exchange at the plasmalemma is involved in regulating the transport of Na+ to the shoot, while calcium plays a key role in limiting the toxic effects of Na+ on integrity of the plasma membrane in root cells. In addition, osmotic adjustment, stomatal closure and leaf abscission appear to play a role. Low and moderate salinity is associated with reduction of CO2 assimilation rate, stomatal and mesophyll conductance. Salinity reduces the fruit weight and oil content while increases the moisture content of fruits. Total phenol content in the olive oil is not affected by moderate NaCl salinity, while the ratio of unsaturated/saturated fatty acids decreases.