Comparative Study of NaCl Salinity in Four Olive Cultivars (Olea europaea L.)

The effects of NaCl salinity on growth, leaf water potential (psi(w)), CO2 assimilation rate (P-n), chlorophyll((a+b)) concentration and fluorescence, total carbohydrates, proline concentration and Na+ and Cl- concentration as indices of salt tolerance of four olive cultivars ('Zard', 'Ascolana', 'Koroneiki' and 'Arbequina') were studied. The plants were grown in black, plastic bags containing sand-perlite mixture (1:1) for five months and were irrigated with half strength Hoagland's nutrient solution containing 0, 25, 50, 75, 100 and 125 mM NaCl. The results indicated significant differences in salt tolerance among the four olive cultivars. 'Zard' was the least tolerant, showing symptoms of chlorosis and necrosis the fourth month of the experiment in the two higher NaCl concentrations. 'Koroneiki' showed toxicity symptoms one month later and the other two cultivars did not show any symptoms during the five months duration of the experiment with the 'Ascolana' being slightly superior to 'Arbequina'. After five months from the beginning of the treatments 'Zard' showed a 40-45% decrease in shoot length growth compared with the control, 'Koroneiki' 23,3-40%, 'Arbequina' 21,4-35% and 'Ascolana' 22,3-29,6%. At the concentration of 125 mM NaCl, 'Zard' showed a decrease in photosynthesis, transpiration, leaf water potential and chlorophyll content of 59, 75, 138 and 58% respectively. The carbohydrate content remained at the same level as the control, while proline content increased by 58%. In 'Ascolana' photosynthesis and leaf water potential decreased by 35 and 166%, respectively, while all the other physiological parameters increased. The corresponding parameters in the two other cultivars had intermediate values. An elevated accumulation of Na+ and Cl- in leaves was recorded by increasing the NaCl concentration in solution in all cultivars with 'Zard' showing the higher one.