Optimization of Seed Germination in Snow Lotus (Saussurea involucrate): Synergistic Effects of PEG-GA 3 -IBA Treatments and Peat-Vermiculite Substrates

Background Saussurea involucrata ( S. involucrata ), a rare medicinal plant of the Asteraceae family, primarily grows in high-altitude cliffs (∼3000 m) in Xinjiang, China. Its dried aerial parts exhibit pharmacological properties such as anti-inflammatory, antioxidant, and antitumor effects. However, wild populations have sharply declined due to environmental changes and human activities, leading to its classification as a nationally protected species (Class II). Artificial cultivation is critical for conservation, but challenges persist: seeds exhibit strong dormancy, low viability, and a short lifespan, coupled with strict environmental requirements (e.g., altitude, temperature), resulting in poor germination rates (< 10%). Previous studies focused on single-factor interventions (e.g., gibberellic acid (GA ₃ )) or substrate optimization but neglected synergistic effects and comprehensive protocols. This study innovatively combines polyethylene glycol (PEG), GA ₃ , and indole-3-butyric acid (IBA) treatments with peat-vermiculite substrates, aiming to establish an optimized protocol for enhancing seed germination and seedling resilience, thereby supporting scalable cultivation. Results Compared with those of the control group, the germination potential increased by 34.1%, the germination rate improved by 26.6%, the germination index rose by 26.67%, the vigor index increased by 94.7%, the length of the roots increased by 257.4%, the activities of three antioxidant enzymes (SOD, POD, and CAT) increased, and the malondialdehyde (MDA) content decreased. Conclusions When a 50% peat soil + 50% vermiculite substrate was used and seeds were soaked with a combination of 25 g/L PEG 4000, 150 mg/L GA ₃ , and 10 mg/L IBA, S. involucrata seeds presented optimal comprehensive performance in terms of seed vigor indices and physiological indicators. Under these conditions, the seeds presented greater germination capacity, improved growth potential, and greater stress tolerance. These experimental results provide technical references for the artificial cultivation of S. involucrata seeds.