A Comparative on the Plant Endogenous Hormones of Transgenic and Non-Transgenic Hybrid Aspen Tissue-Cultured Plantlets Genetic Diversity of Section Leuce in Populus Along the Erqis River Morphological and Anatomical Features during the Formation of Adventitious Roots of Populus tremula×P.tremuloides by Micro-cuttage Multiplication Association Analysis Between Autumn Senescence and SNPs in the Candidate Genes of Populus tremula Microdissection, in Situ Analysis and Microcloning of Poplar Chromosome 1 Microdissection, in Situ Analysis and Microcloning of Poplar Chromosome 1 Change of Endogenous Plant Hormones of Vitrificated Plants of Hybrid Aspen by Tissue Culture A Study on Genetic Diversity of Populus tremula in China by Single-copy Nuclear Markers