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.

Potential shifts in the suitable habitat of limestone-dwelling plant species due to climate change are of considerable biogeographical significance. The species distribution was projected using maximum entropy (MaxEnt) modeling, a widely recognized approach based on machine learning and statistical analysis. This study utilizes the MaxEnt model to develop a potential distribution map for Rhododendron micranthum, examining its spatial patterns to forecast potential impacts under both present and future climate scenarios. The model exhibited robust performance, with a notably high average area under the curve (AUC), underscoring its reliability and accuracy. Its effectiveness in predicting species distributions based on climate datasets provides critical insights into the potential habitats of limestone regions. A significant contribution of this model lies in its capacity to inform future field surveys, monitoring activities, and management strategies. The findings of this study indicate significant variability in results depending on the climate dataset utilized, underscoring the importance of meticulous selection of climate variables. Ultimately, the application of this model deepens our understanding of regional ecological dynamics and climate behavior, offering a solid scientific basis for biodiversity conservation. Focused conservation efforts in climate-sensitive areas, particularly for geographically isolated species, could accelerate research and lead to more effective species management approaches.

The genus Pseudolysimachion (Plantaginaceae) is currently considered a subgenus of Veronica, though its independent status is still debated. In Korea, Veronica subgenus Pseudolysimachion is diverse, including widespread Veronica longifolia (formerly Pseudolysimachion longifolium) and endemic Veronica pusanensis (formerly Pseudolysimachion pusanensis), both valuable for horticulture. Despite chloroplast genome utility in plant phylogenetics and breeding, complete chloroplast genome data for these key species were absent. To address this gap, we sequenced, assembled, and characterized the complete chloroplast genomes of V. longifolia and V. pusanensis. The complete chloroplast genomes of V. longifolia (152,237 bp) and V. pusanensis (152,250 bp) displayed typical quadripartite structures and encoded 133 genes (88 protein-coding, 37 tRNA, 8 rRNA). Phylogenetic analysis strongly supported the monophyly of the Veronica subgenus Pseudolysimachion clade, which is nested deeply within the genus Veronica. Our findings provide essential genomic resources that clarify phylogenetic relationships within the subgenus and contribute significantly to the broader taxonomic resolution of the tribe Veroniceae. These results firmly establish the taxonomic positions of the Korean endemic species, V. longifolia and V. pusanensis, and offer crucial genomic insights into speciation patterns and evolutionary trends within the genus, thereby supporting future plant breeding and germplasm utilization strategies.

Climate change necessitates a deeper understanding of plant tolerance mechanisms to dual water stresses. This study investigated the distinct physiological and genetic responses of Longleaf Speedwell (Pseudolysimachion longifolium) to drought and waterlogging using RNA-Seq. Physiological data showed a rapid and comparable reduction in photosynthetic efficiency after one week and biomass under both stresses after two weeks. However, transcriptomic analysis revealed fundamentally distinct strategies: Drought induced a massive transcriptional upheaval (5 times more DEGs), characterized by the upregulation of defense pathways (e.g., Phenylpropanoid biosynthesis) and the severe shutdown of growth-related metabolism (e.g., Ribosome, Photosynthesis). In contrast, waterlogging triggered a constrained hypoxic response, prioritizing energy conservation by downregulating synthesis processes (Nitrogen, Arginine biosynthesis) and activating ethylene signaling. The reliability of the RNA-Seq data was confirmed by qRT-PCR, which also crucially identified Alcohol dehydrogenase (ADH), Ethylene Responsive Factor (ERF), and Peroxidase (POD) as common candidate genes highly induced under both drought and waterlogging conditions, suggesting a generalized role in broad-spectrum water stress tolerance. These findings provide critical molecular evidence demonstrating the divergent and specific adaptive strategies of P. longifolium to different water regimes and highlight ADH, ERF, and POD as promising targets for engineering broad-spectrum water stress tolerance.