Abstract
Sago palms at the 17th or 19th leaf stage maintained low Na+ concentrations in the leaflets by storing Na+ in the roots and petioles at lower leaf positions under 86mM NaCl (corresponding to 0.5% NaCl) treatment for 30 days. The K+ concentrations did not decrease in the roots, leaflets and petioles, regardless of the leaf position. The Na+ concentrations in the roots of the seedlings at the 8th leaf stage clearly increased with increasing NaCl concentration in the culture solution (86, 171 and 342mM NaCl correspond to 0.5, 1.0 and 2.0% NaCl), with a maximum increase of 3.1 times. In the petioles, the Na+ concentrations tended to be higher at higher concentrations of NaCl, but with a maximum increase of 1.5 times. The Na+ concentrations in the leaflets did not show any distinct differences. Sago palm might exhibit an avoidance mechanism to maintain low Na+ concentrations in the leaflets by storing Na+ in the roots and petioles, hence preventing Na+ distribution to the leaflets up to the 342mM (2.0%) NaCL treatment. K+ absorption and distribution in the leaflets were not affected by the storage of Na+ in the roots and petioles in sago palm. However, the transpiration rate under the 342mM NaCl treatment tended to be lower than that at lower NaCl concentrations. It was, therefore, considered that sago palm tolerated up to 171mM (1.0%) NaCl concentration for at least 30 days.
