In the many parts of the world where water is in short supply, plant water use efficiency, the ratio of carbon fixation to water loss, is critical to plant survival, crop yield and vegetation dynamics. So much effort is being made to reduce water use by crops and produce more crops per drop. Promoting plant water use efficiency is one of the most significant strategies to save water. For the evidence of variation in WUE among species, cultivars and populations.Therefore, it is of great significance to cultivate and choose good WUE clone. Populus deltoides is one of the most important species for largescale forestation projects in china. However, the trait of high- consumption-water becomes the key limited factor in the arid and semi-arid areas In our test, Carbon isotope discrimination (δ¹³C) is a measure of the ¹³C/¹²C ratio in plant material, and is positively correlated with WUE. We therefore examined δ¹³C to assess WUE in our study, the average ¹³C/¹²C of NE-19, R-270 and DN-2 was -29.732,-30.758 and -31.606, respectively. For farmers and agronomists, the unit of production (WUEL) is much more likely to be the yield of harvested product achieved from the water made available to the crop through rainfall or irrigation. In our study, we found that the WUEL of NE-19, R-270 and DN-2 was 2.41, 2.12 and 1.98 mg/ml, respectively.Although WUE can be studied by many strategies, little is known about the genetic control of transpiration efficiency Our interest has therefore focused on identifying genes whose function could increases plant water use efficiency (WUE). Thus, finding new key genes responsible for water use efficiency phenotypes is of great importance not only for a better understanding of stress responses, but also for promising future crop improvement. The ERECTA gene regulates plant transpiration efficiency in Arabidopsis. In our paper, A cDNA clone, designated PdERECTA, was isolated from Populus deltoids. And the cDNA of PdERECTA was 2844bp and contained a single open reading frame of 948 amino acid residues. The deduced amino acid sequence of PdERECTA shows characteristics of a transmembrane receptor protein kinase with distinct domains: extracellular domain; transmembrane domain; intracellular kinase domain. To determine which type of stress could induce PdERECTA expression, total RNA was extracted from One-year-old NE-19 treated with various stress. qRT-PCR indicated that mRNA accumulation of PdERECTA was induced by low temperatures 、salt stress、 abscisic acid (ABA) 、Dehydration. In order to further determine the pattern of tissue specific expression of PdERECTA under well-water conditions, different organs of were harvested for RNA extraction.In the paper, we also found that PdERECTA was strongly expressed in top-leaves, weakly in immature-leaves but not in senescent- leaves and roots, indicating its function in normal plant growth and development.