A Study on the Environmental Adaptation Mechanism of Plants in Hanzhong Tiankeng

Tiankeng ecosystems are characterized by strong microenvironmental gradients that influence plant adaptation; however, the molecular mechanisms underlying plant responses to altitudinal variation remain poorly understood. In this study, transcriptome sequencing and bioinformatic analyses were conducted to investigate the environmental adaptation mechanisms of three representative plant species (Hydrangea strigosa Rehder, Pilea martini, and Pilea sinofasciata) distributed along the vertical gradient of the Hanzhong Tiankeng in Shaanxi Province, China. Differential gene expression and functional enrichment analyses were performed to explore transcriptional responses under different altitude conditions. The results showed that flower coloration in Hydrangea strigosa Rehder was associated with the activation of sugar metabolism and triterpenoid biosynthesis pathways, suggesting potential indirect roles in modulating cellular metabolism and physiological conditions linked to flower coloration, while poor growth at the tiankeng bottom was associated with enhanced cellular respiration under low-light conditions, suggesting a potential link between energy metabolism and growth performance. In contrast, Pilea martini and Pilea sinofasciata exhibited better growth in the pit-bottom environment. Pilea martini promoted growth through enhanced carbohydrate metabolism and tricarboxylic acid cycle activity, whereas Pilea sinofasciata responded to environmental stress through hormone signaling, triterpenoid biosynthesis, and light signaling pathways. These findings reveal species-specific molecular strategies for plant adaptation to altitude-related environmental gradients in tiankeng ecosystems and provide insights into plant survival mechanisms in karst habitats.