Seed Germination and Responses of Five Native Veronica Species Under Salinity Stress in Korea

This study analyzed the seed germination characteristics and physiological responses of five Korean Veronica species (V. daurica, V. nakaiana, V. kiusiana var. glabrifolia, V. pusanensis, and V. pyrethrina) under salinity stress. Preliminary experiments on five Veronica species using various NaCl concentrations revealed that treatment with 150 mM NaCl almost completely inhibited seed germination, whereas treatment with >50 mM NaCl significantly decreased seed germination rate and index. Therefore, this study focused on the effects of treatment with 0, 50, and 100 mM NaCl for 7 days on the germination rate, germination index, germination energy, germination vigor index, water content, fresh weight, dry weight, and root length of the plants. When treated with 100 mM NaCl, most species had few survivors after 5 days, even if germination had occurred. Almost all parameters significantly decreased with increasing NaCl concentration. Especially, fresh weight and water content decreased with increasing NaCl concentration, while dry weight did not show a significant response to NaCl concentration, suggesting that salinity stress inhibited water uptake, which is crucial for seed germination. Hormonal analysis revealed the presence of indole-3-acetic acid (IAA) and abscisic acid (ABA) and the absence of gibberellic acid. Most species showed no significant changes in IAA and ABA levels with varying NaCl concentrations. However, V. pusanensis showed significantly increased ABA levels with increasing NaCl concentration, and V. daurica showed significantly higher IAA levels at 100 mM NaCl than at other NaCl concentrations. This study demonstrates that salt stress negatively affects Veronica seed germination, with varying intensities among species.