Na⁺ and K⁺ Concentrations in Different Plant Parts and Physiological Features of Metroxylon warburgii Becc. under Salt Stress

Abstract

Na⁺ and K⁺ concentrations in different plant parts and some physiological features under NaCl solution treatment were investigated to study the absorption and distribution of Na⁺ and K⁺ inMetroxylon warburgii (Heim) Becc. that belongs to same genus with sago palm (M. saguRottb.) in the palm family. Seedlings at the 11th or 13th leaf stage were used for the treatment of 342mM (2%) NaCl in a green house under natural sun light in mid summer in central Japan.M. warburgiimaintained a low Na⁺ concentration in the leaflets of upper active leaves by storing Na⁺ mainly in the petioles at lower leaf positions under the NaCl treatment for 36 days. The Na⁺ concentrations in the roots were lower in the steles than in cortices, and this result suggests the existence of a mechanism to restrict the over influx of Na⁺ from the cortex into the stele of the roots. The K⁺ distribution to the leaflets was not affected by the change in the Na⁺ concentration in the roots and petioles inM warubrugii. Photosynthetic rate decreased with the NaCl treatment, which was attributed to decrease in stomatal conductance and chlorophyll content per unit leaf area.