Response of Two Olive Cultivars to Salt Stress and Potassium Supplement

ABSTRACT

The effects of saline water containing 0, 50, 100, and 150 mM sodium chloride (NaCl), and 100 mM NaCl + 100 mM potassium (K) on photosynthesis, water relations, and ion and carbohydrate content of olive (Olea europaea L.) cultivars ‘Koroneiki’ and ‘Mastoidis’ were studied on five-year-old trees. Salinity increased sodium (Na⁺) and chloride (Cl⁻) in tissues of both cultivars, but more so in ‘Koroneiki’ than in ‘Mastoidis.’ Salt-toxicity symptoms were observed at 100 and 150 mM, but not in plants receiving extra K. In salt-stressed plants, leaf water potential declined, whereas turgor potential remained positive due to a rapid decrease in osmotic potential. Salinity increased mannitol content up to 41.3% in ‘Mastoidis’ and 15.8% in ‘Koroneiki’, but reduced starch content in leaves. Photosynthetic rates fell significantly with increasing salinity in both cultivars, but more so in ‘Koroneiki’ than in ‘Mastoidis’. Potassium supplements reduced the concentration of Na⁺ and increased the concentrations of K⁺ in leaves, but decreased photosynthesis.

Keywords:

• salinity
• photosynthesis
• water relations
• potassium
• carbohydrates
• olive

ACKNOWLEDGMENTS

This work was partly supported by PEP Kritis 1996–2000. The assistance of Mr. G. Papadakis, Mr. E. Kokolakis, and Ms. N. Digalaki during the measurements is gratefully acknowledged. We would also like to express many thanks to Susan Coward for correcting the final manuscript.

Notes

^x Values represent the mean of four replications. Means within each column separated by different letters are significantly different (P < 0.05, LSD-test).

^x Values represent the mean of four replications. Means within each column separated by different letters are significantly different (P < 0.05, LSD test).

∗ p < 0.05

∗∗: < 0.01, NS: non-significant.

^x Values represent the mean of four replications. Means within each column separated by different letters are significantly different (P < 0.05, LSD test).

^x Values represent the mean of four replications. Means within each column separated by different letters are significantly different (P < 0.05, LSD test).