Puccinellia tenuiflora is a halophyte with remarkable adaptability to the combined stress of saline and stagnant. The apoplastic barrier formed by endodermal thickening is likely crucial for this adaptation， in which the Casparian strip and suberin lamellae serve as key apoplastic barriers in endodermis for the radial transport of water and solutes. In this study， using Puccinellia tenuiflora as material， we cloned PtCASP1， a key gene involved in Casparian strip formation. Bioinformatic analysis， subcellular localization， and expression pattern analysis under saline， stagnant and combined saline-stagnant stresses were conducted. The results showed that the PtCASP1 gene was 552 bp in length， encoding 184 amino acids. It was a hydrophobic， stable protein and contained cis-acting elements responsive to gibberellin， drought stress， low temperature stress， and light response. Phylogenetic analysis indicated that PtCASP1 was closely related to those in Lolium multiflorum and Alopecurus aequalis. Immunofluorescence analysis revealed that the PtCASP1 protein exhibited dual localization in the nucleus and cell membrane. The expression level of the PtCASP1 gene in the roots of Puccinellia tenuiflora was significantly higher than that in the leaves， and it responded to saline， stagnant， and combined saline-stagnant stresses， with the highest relative expression levels at 72 hours post-treatment for all stress conditions. This study provides a reference for further investigation into the function of the Casparian strip in helping Puccinellia tenuiflora adapt to saline-stagnant combined stress.

Puccinellia tenuiflora  /  PtCASP1  /  Gene cloning  /  Subcellular localization  /  Expression analysis  /  Combined saline-stagnant stress