Suaeda japonica M. is a kind of typical halophyte in Japan. The objectives of this study were to clear the response of S. japonica plants under saline environments (0.3(control)), 3 or 6% NaCl treatment cultivation), morphological and physiological features, and utilization of the plants as forage, by comparing with the features of another kind of halophytes, Salicornia europaea L. which is S-type from Okayama prefecture (common name is glasswort or saltwort). Plant heights and dry weights of S. japonica were higher than those of S. europaea at harvest day under 0.3 and 3% NaCl treatment. It was obvious that Na was accumulated more in leaves than in shoots or roots of S. japonica, and Na content of S. japonica plant increased along with the increase of salt treatment concentration. On the other hand, K, Ca and Mg content of S. japonica decreased with the increase of treated salt concentration. Crude protein contents of leaves of S. japonica were increased with the increase of treated salt concentration. Both of halophytes, S. europaea and S. japonica showed very high salt tolerance. Therefore they are very useful to green the salt affected land or as a forage crop because of high content of crude protein. Both halophytes showed high Na content. But S. japonica is more promising than S. europaea as a forage crop because Na content of S. japonica was lower than that of S. europaea.
Na+, K+, Ca2+, Mg2+ and Cl- concentrations in different plant parts and some physiological characteristics under NaCl treatment in solution culture were determined to investigate the salt resistance of sago palm. Seedlings at the 8th or 9th leaf stage were used for the treatment of 342mM (2%) NaCl in a phytotron at 30°C and 75% relative humidity under natural sunlight in mid summer in central Japan. Sago palm maintained a low Na+ concentration in the leaflets of active leaves at higher positions eventually, by storing Na+ mainly in the roots and the petioles at lower positions under the NaCl treatment applied for 31 days. The Na+ concentrations in the large roots were lower in the stele than in the cortex under the NaCl treatment, which suggested that the endodermis possessed a mechanism to restrict the excess influx of Na+ from the cortex into the stele. Based on X-ray micro-analysis, a dense distribution of Na was observed around the endodermis of the large roots. The changes in the Na+ concentration in the roots and leaves did not affect the K+ distribution to the leaflets and petioles. The effect of the increase of the Na+ concentration in the seedlings on Ca2+ and Mg2+ distribution to the leaflets was small. Regardless of the remarkable decrease in the transpiration rate and slight delay in the emergence of new leaves with the NaCl treatment, there was no significant difference in dry matter weight of the leaflets and petioles at each leaf position. It was, therefore, considered that salt resistance of sago palm might be due to salt avoidance to mechanically restrict an excess of Na distribution in plant tissues and also to maintain the water status in the leaves by restricting the transpiration.
Na+, K+, Ca2+, Mg2+ and Cl- concentrations in different plant parts and some physiological characteristics under NaCl treatment in solution culture were determined to investigate the salt resistance of Metroxylon vitiense (H. Wendl.) H. Wendl. ex Benth. & Hook. f. that belongs to the same genus as sago palm (M. sagu Rottb.). Seedlings at the 11th to 13th leaf stages were used for the treatment of 342mM (2%) NaCl for 31 days in a phytotron at 30°C and 75% relative humidity under natural sunlight in mid-summer in central Japan. The Na+ and Cl- concentrations increased in the roots, petioles and leaflets with the NaCl treatment, while, the K+ concentration did not change in the top parts. The Ca2+ and Mg2+ concentrations increased in the leaflets, especially at lower and higher leaf positions, respectively. Leaf emergence and dry matter weight of the top parts were not affected by the NaCl treatment, whereas the transpiration rate decreased. It was, therefore, considered that salt avoidance to maintain the water status in the leaves by restricting the transpiration is important for the salt resistance of M. vitiense. The changes in the Ca2+ concentration can be considered to play a role in adequate absorption of K+, which would enable the plant to maintain osmotic adjustment in the leaflets.