以原产地和入侵地加拿大一枝黄花（Solidago canadensis Linn.）二倍体、四倍体和六倍体幼苗为实验材料，对子叶期幼苗和子叶的形态特征，以及真叶期（包括第一和第二真叶期）第一真叶的形态特征进行了比较。结果表明：在子叶期，原产地和入侵地加拿大一枝黄花四倍体和六倍体的全株长、地上部长度、根长、根长与全株长的比值、茎直径以及子叶的长度、宽度和面积均显著高于二倍体，且四倍体和六倍体的上述指标间差异不显著；在真叶期，原产地和入侵地加拿大一枝黄花四倍体和六倍体第一真叶的长度、宽度和面积均显著高于二倍体，且六倍体的上述指标在第一真叶期显著高于四倍体，但在第二真叶期与四倍体差异不显著。入侵地各细胞型加拿大一枝黄花子叶期和真叶期的上述指标总体上显著高于原产地，但其子叶期子叶长度与宽度的比值却显著低于原产地，说明原产地加拿大一枝黄花的子叶更为狭长。研究结果显示：入侵地加拿大一枝黄花多倍体幼苗具有明显的生长优势，狭长的子叶是其二倍体的特征，可以作为早期鉴别的依据。

Taking diploid， tetraploid， and hexaploid seedlings of Solidago canadensis Linn. from native and introduced ranges as research materials， morphological characteristics of seedling and cotyledon at cotyledon stage and that of the first true leaf at true leaf stage （including the first and the second true leaf stages） were compared. The results show that at cotyledon stage， whole plant length， above-ground part length， root length， ratio of root length to whole plant length， stem diameter， and length， width and area of cotyledon of tetraploid and hexaploid of S. canadensis from native and introduced ranges are significantly higher than those of diploid， and there is no significant difference in above indexes between tetraploid and hexaploid； at true leaf stage， length， width， and area of the first true leaf of tetraploid and hexaploid of S. canadensis from native and introduced ranges are significantly higher than those of diploid， and above indexes of hexaploid at the first true leaf stage are significantly higher than those of tetraploid， but have no significant difference with those of tetraploid at the second true leaf stage. Above indexes of different cellular types of S. canadensis from introduced range at cotyledon and true leaf stages are generally significantly higher than those from native range， but its ratio of length to width of cotyledon at cotyledon stage is significantly lower than that from native range， indicating that cotyledon of S. canadensis from native range is longer and narrower. It is suggested that polyploid seedlings of S. canadensis from introduced range have obvious growth vigor， and long and narrow cotyledon is the characteristic of its diploid， which can be used as a basis for early identification.