Red-osier dogwood (Cornus stolonifera Michx, Syn. Cornus sericea), a species relatively well adapted to moderately saline conditions compared with other boreal species, was used to test the effects of NaCl on plant water relations, cell wall elasticity, and cell wall composition of seedlings. Three month-old seedlings were treated hydroponically with 0, 25, and 50 mm NaCl for 21 days. The osmotic potential at full turgor, osmotic potential at turgor loss, pressure potential at full turgor, and relative water content at turgor loss of red-osier dogwood shoot tissue were not significantly affected by the NaCl treatments. Cell wall elasticity of the shoot tissues did not change following NaCl treatments, suggesting that elastic adjustment did not play a role in the adaptation mechanism. Hemicellulose content of the cell wall increased in salt treated seedlings. The primary sugar found in the cell wall hemicellulose fraction was xylose. In the pectin fraction arabinose and galacturonic acid were the main sugars. Sodium chloride stress did not alter the sugar composition of the hemicellulose fraction; however, NaCl did increase the amount of rhamnose in the pectin fraction. The results of this study suggest that at moderate salinity red-osier dogwood does not make any osmotic or elastic adjustments in the shoot tissue, but some changes in the cell wall composition do occur. These changes could contribute to the decrease in growth recorded in red-osier dogwood during NaCl stress.

A greenhouse study was designed to test the response of red-osier dogwood (Cornus sericea L.) to NaCl during the onset of bud break. Seedlings treated with 50 mmol·L–1 NaCl for 32 d had lower shoot dry mass and shoot height than untreated seedlings. Transpiration and photosynthetic rates, chlorophyll b and carotenoid concentrations of red-osier dogwood seedlings were significantly reduced by NaCl treatment. The shoots of seedlings treated with 50 mmol·L–1 NaCl had a higher bulk modulus of cell wall elasticity than those of untreated seedlings, but the water potential components determined from the pressure-volume curves, osmotic potential and pressure potential at full turgor and osmotic potential at pressure loss, suggest that this change did not contribute to salt tolerance. Minor changes, including a small increase in arabinose of the hemicellulose fraction and a decrease in both galactose and rhamnose of the pectin fraction, also occurred in response to NaCl treatment. These changes in cell wall composition and elasticity could be partly attributed to differences in the developmental stage of the shoot tissues resulting from the delay in bud breaking in salt treated plants.