Physiological and biochemical adaptation of Phedimus aizoon L. to karst high calcium soils and associated antioxidant and hypoglycemic activities: comparison with normal soil

Rocky desertification is a major ecological constraint in karst regions, where excessive soil calcium availability can limit plant growth and development. Phedimus aizoon L., a calcium‑accumulating vegetable with nutritional and medicinal value, exhibits tolerance to abiotic stress. However, the physiological and biochemical basis of its response to karst high‑calcium soils remains insufficiently understood. In this study, P. aizoon grown in normal soil and karst high‑calcium soil was compared to assess growth performance, calcium accumulation, antioxidant responses, and functional traits. Relative to normal soil, karst high‑calcium soil inhibited shoot growth by 25.43% while promoting root development, accompanied by a 2.79‑fold increase in soluble calcium content in roots. This growth adjustment was associated with increased levels of malondialdehyde, proline, and phenolic compounds (1.09-1.40‑fold), together with enhanced antioxidant enzyme activities (1.10-1.43‑fold). In addition, quality‑related functional traits were enhanced, including a 68.74% increase in total antioxidant capacity (T‑AOC) and higher in vitro hypoglycemic activity, with α‑glucosidase and α‑amylase inhibition increasing by 34.52% and 29.59%, respectively. These findings indicate that P. aizoon responds to karst high‑calcium conditions through coordinated metabolic regulation, involving changes in osmoprotective and phenolic compound accumulation. During this process, quality‑related functional traits, such as antioxidant activity and in vitro hypoglycemic potential, were also enhanced. Overall, these results provide a physiological and biochemical basis for the sustainable utilization and cultivation of P. aizoon in rocky‑desertified karst regions.