ION CONTENTS, RELATIVE ELECTROLYTE LEAKAGE, PROLINE ACCUMULATION, PHOTOSYNTHETIC ABILITIES AND GROWTH CHARACTERS OF OIL PALM SEEDLINGS IN RESPONSE TO SALT STRESS

Oil palm seedlings were photo-autotrophically grown in MS medium and subsequently exposed to 0 (control), 25, 50, 100 or 200 mM NaCl. Sodium ions, proline content and the percentage of relative electrolyte leakage in seedlings subjected to salt stress increased, depending on the degree of salt concentrations. Sodium ion accumulation in oil palm seedlings grown under 200 mM NaCl was enriched and positively related to membrane injury or relative electrolyte leakage subsequently correlated with total chlorophyll degradation. Chlorophyll a (Chl(a)), chlorophyll b (Chl(b)), total chlorophyll (TC), total carotenoids (Cx+c), maximum quantum yield of PSII (F-v/F-m), photon yield of PSII (Phi(PSII)) and quantum efficiency of PSII (qP) in the seedlings under salt stress dropped significantly in comparison to the control group, leading to a reduction in net-photosynthetic rate (P-n) and growth, especially in 200 mM NaCl. A positive correlation between physiological and growth parameters, including sodium ion, relative electrolyte leakage, photosynthetic pigments and water oxidation in photosystem II, P-n and plant dry weight was found. These data may further be applied to establish criteria for salt tolerance screening in oil palm breeding programs.