Abstract: To determine water stress is the key factor influencing the Populus euphratica seedling growth and survival rate,and seedling response to moisture.We took Populus euphratica seeds as study material to study Populus euphratica seedling root growth characteristics for different relative water content by the soil pot method.The results showed that Populus euphratica seedling root surface area decreased with decreasing of soil moisture,and the seedling root surface area by intermittent treatment was slightly larger than the treatment given by continuous treatment when the water content was in the same conditions.The seedling root biomass by intermittent treatment was significantly less than the seedlings under continuous treatment,and the minimum root biomass occurred when soil water content was only 5%.It evidenced that the state of drought stress influences seedling root biomass accumulation.Root length of continuous water treatment was greater than the length of the intermittent treatment in the moisture gradient,but the root width to depth ratio was less than that of the seedling by intermittent treatment.The lateral branching angle of seedlings by intermittent treatment was greater than that of the continuous ones.This study verified the water stress was the key factor influencing Populus euphratica’s seedling growth.And the seedlings can change the expansion direction and the accumulation of biomass to adapt to the state of drought stress.

Key words: Populus euphratica, seedling, root system, growth, architecture