However, few studies have been reported on the enhancement of multiple pathways associated with a polygenetic trait by introduction of multigenes in forest trees. Since differential agronomic traits such as salt tolerance and insect resistance are commonly controlled by distinct genes, engineering of multiple genes that control distinct metabolic pathways would represent a significant progress toward the goal of simultaneous enhancement of multiple characteristics in woody species. Physiological parameters for each treatment were measured at the midpoint of the experiment when the leaves of some plants were observed to be yellowing and exhibiting signs of chlorosis. It Publications Using Abomle FTY720 should be noted that only data from the lines exposed to 0 and 50 mM NaCl were obtained at the termination of the experiment because of the substantial loss of leaves in the lines tested with 85 or 135 mM NaCl treatments. For this same reason, biomass data was collected without considering the contribution of leaves at the end of the experiment. Under salt stress, transgenic lines showed mild stress symptoms and had more and longer adventitious roots than the control . The transgenic trees exhibited an average increase in height of 87.18% under normal conditions and 46.16- 207.10% under salt stress conditions . The basal diameter also significantly increased to 70.32% greater than that of the control line upon exposure to 135 mM NaCl . The improved growth in plant height and basal diameter resulted in a significant increase in stem biomass under salt stress conditions . Under moderate and severe stress conditions, transgenic lines accumulated more root biomass than the control. On day 40, WUEi values gradually rose with increasing concentrations of salt treatments from 0 to 85 mM NaCl, and decreased at 123 mM NaCl treatment, altogether with generally higher values for the transgenic lines . On the last test day of the 50 mM NaCl treatment, the WUEi levels of the multigene lines were similar to those on day 40 . The WUEi of non-transgenic plants, however, declined to about 80.74% of the 40 day level . Chlorophyll concentrations showed an overall downward trend with increasing salt stress, while higher values in the transgenic lines were apparent with 135 mM NaCl treatment . When exposed to 50 mM NaCl, the chlorophyll concentration of the multigenetransformed poplar tended to be higher relative to the control plants, but it was not significantly different at test termination .