苏铁属（Cycas）作为一类古老的裸子植物，经历了漫长的演化历史，因此，深入研究其形态特征与环境的相互关系，有望为古环境重建提供重要参考依据。本文分析西双版纳和深圳两地植物园栽培环境下27种苏铁属植物的叶表皮特征及气孔参数的差异，并进一步探讨气孔参数与系统发育的关系。结果表明：（1）苏铁属内叶表皮特征保守稳定，具有一定的分类学意义：依据表皮细胞及气孔器特征划分了四种叶表皮类型，可为苏铁现生植物或化石的鉴定提供参考。（2）四种叶表皮类型指示了不同的原生生境特征，对古环境具有一定的指示意义。（3）同一环境下，气孔参数在属内的种间差异显著，其次，气孔指数在属内变化与系统发育有关，除气孔指数具显著的系统发育信号外，其余气孔参数均无显著系统发育信号。本研究结果表明气孔参数法重建古大气CO2浓度时，需尽可能利用亲缘关系相近、叶表皮和生境皆相似的代理种，并明确气孔参数与大气CO2分压的相关关系在种间的异同，从而提高该方法的有效性。

Cycas is a group of gymnosperms with a long evolutionary history. This study is to investigate the relationship between the leaf epidermal morphology of Cycas and the environment to provide fundamental evidences for palaeoenvironmental reconstructions. In this study, we compared the epidermal characters and stomatal parameters of 27 Cycas species in the garden culturing environment and then analyzed the phylogenetic signals of stomatal parameters. The present study mainly found that: 1) the epidermal characters of Cycas were generally conservative within species and it has taxonomic significance. These 27 Cycas species could be classified into four types according to their epidermal cells pattern and other characters of stomata apparatus. The above result indicated that leaf epidermal characters can be used for identifying extant or fossil Cycas species; 2) Four leaf epidermal types were related to their natural habitats; therefore, the combination of different leaf epidermal characters may be a good indicator for palaeoenvironment; 3) Species included in this study varied in stomatal parameters despite they grew under the same cultivating environment. The variation of Stomatal Index (SI) within Cycas was associated with phylogeny: the SI presented with significant phylogenetic signal, whereas the phylogenetic signals of other stomatal parameters were weak. This study indicated that, when using the stomatal density/index method to reconstruct palaeo-atmospheric CO2 concentration, it should be cautiously considered to choose nearest living species as proxies, especially these with similar morphology, habitat and close phylogenetic relationship. In addition, the relationship between stomatal parameters and CO2 partial pressure (pCO2) should be clarified within a genus so as to improve the effectiveness of this method.

中国科学院前沿科学与教育局重点研究项目基金（No. QYZDB-SSW-SMC016）和中国科学院青年创新促进会项目基金（No. 2017439）联合资助。