Physiological and transcriptomic analyses reveal the mechanisms of clonal integration in Leymus chinensis supporting daughter ramets under alkali stress

Leymus chinensis is a typical clonal plant and dominant species in alkalized grasslands of northern China. It has been verified that clonal integration mediates alkali stress tolerance of this species via supporting mother ramets to daughter ramets, but the mechanisms remain poorly understood. In this study, we investigated physiological and transcriptomic responses of mother ramets and daughter ramets (integration and cutting) of L. chinensis under alkali stress, with a focus on the role of clonal integration in enhancing stress tolerance in daughter ramets. Physiological analyses revealed that under alkali stress, compared with cutting treatments, clonal integration enhanced photosynthetic capacity, reduced Na + accumulation, and maintained K + homeostasis in daughter ramets. In contrast, integrated mother ramets exhibited enhanced Na + toxicity, decreased photosynthesis, and increased oxidative damage, suggesting a resource reallocation strategy prioritizing daughter ramet survival. In addition, transcriptomic analyses elucidated the underlying molecular basis. Compared with control groups, alkali stress strongly enhanced the upregulation of 57 sugar metabolism and 19 glycolysis genes, 15 ion homeostasis genes, 100 ROS-scavenging-related genes (including 4CL , PAL , and POD ), and 26 ethylene signaling genes in integrated daughter ramets. Crucially, compared with their respective controls, these key genes remained unchanged or downregulated in cutting daughter ramets under alkali stress. This integration-driven activation systematically supported energy assimilation, stable Na + /K + balance, antioxidant defense, and stress alleviation. Collectively, these findings demonstrated that clonal integration in L. chinensis functions as a protective mechanism for daughter ramets under alkali stress through coordinated regulation of photosynthetic maintenance, ion homeostasis, antioxidant defense, and hormone signaling.