Ectomycorrhizal fungus (Paxillus involutus) and hydrogels affect performance of Populus euphratica exposed to drought stress Zhi-Bin Luo, Ke Li, Xiangning Jiang and Andrea PolleAnn. For. Sci., 66 1 (2009) 106DOI: https://doi.org/10.1051/forest:2008073