Veronicastrum sibiricum is a perennial species distributed in Korea, Japan, Manchuria, China, and Siberia. This study aimed to determine the requirements for germination and dormancy break of V. sibiricum seeds and to classify the kind of seed dormancy. Additionally, its class of dormancy was compared with other Veronicastrum and Veronica species. V. sibiricum seeds were permeable to water and had a mature embryo during seed dispersal. In field conditions, germination was prevented by physiological dormancy, which was, however, relieved by March of the next year, allowing the start of germination when suitable environmental conditions occurred. In laboratory experiments, the seeds treated with 0, 2, 4, 8, and 12 weeks of cold stratification (4 °C) germinated to 0, 79, 75, 72, and 66%, respectively. After the GA₃ treatment (2.887 mM), ≥90% of the seeds germinated during the four incubation weeks at 20/10 °C. Thus, 2.887 mM GA₃ and at least two weeks at 4 °C were effective in breaking physiological dormancy and initiating germination. Therefore, the V. sibiricum seeds showed non-deep physiological dormancy (PD). Previous research, which determined seed dormancy classes, revealed that Veronica taxa have PD, morphological (MD), or morphophysiological seed dormancy (MPD). The differences in the seed dormancy classes in the Veronicastrum-Veronica clade suggested that seed dormancy traits had diverged. The results provide important data for the evolutionary ecological studies of seed dormancy and seed-based mass propagation of V. sibiricum.

Abiotic stresses severely constrain the growth, yield, and quality of horticultural plants, collectively posing major challenges to sustainable production under changing climatic conditions. Nitric oxide (NO) is a key signaling molecule that modulates plant responses to abiotic stress by integrating with redox regulation systems, hormonal crosstalk pathways, ion homeostasis mechanisms, and transcriptional control networks. Rather than functioning as an isolated regulator, NO participates in dynamic signaling frameworks whose outcomes depend on concentration, timing, cellular redox status, and interaction with other signaling molecules. This review synthesizes current knowledge on NO-mediated mechanisms contributing to abiotic stress tolerance and examines their relevance to sustainable horticultural crop management. After outlining the historical recognition of NO as a plant signaling molecule, we discuss stress-responsive NO-dependent processes, including S-nitrosylation-based post-translational modification, NO–reactive oxygen species (ROS) interactions, and the modulation of stress-responsive transcriptional programs. The roles of NO in tolerance to drought, salinity, extreme temperature, and heavy metal stress are analyzed with emphasis on experimentally supported physiological and molecular responses. We further evaluate evidence from fruit, vegetable, ornamental, and medicinal crops, highlighting how NO-associated signaling correlates with yield stability, quality-related traits, and post-harvest performance under stress conditions. Finally, NO-based strategies such as priming, donor application, and integration with biostimulants are critically assessed in the context of climate-resilient and sustainable horticulture, with attention to translational constraints and field-level feasibility. By connecting mechanistic insights with applied considerations, this review provides a structured framework for evaluating the potential and limitations of NO-based approaches in abiotic stress management of horticultural crops.

Acer tegmentosum, an indigenous medicinal plant under threat from overexploitation, is a deciduous tree species native to Northeast China, southern regions of the Russian Far East, and Korea. In this study, we analyzed the characteristics of samaras (single-seeded fruit) of A. tegmentosum to determine the type of seed dormancy as well as to identify the factors responsible for dormancy release. We identified the seed dormancy to be that of deep physiological dormancy (PD). PD can be combined with mechanical resistance of the seed coat, which limits the protrusion of the radicle during germination. We observed that mechanical resistance exhibited by the water-permeable testa is associated with PD of A. tegmentosum. This was previously attributed to seed dormancy in Acer as testa-imposed dormancy or embryo dormancy. In A. tegmentosum, PD and mechanical resistance of the testa were overcome through cold stratification treatment at 1 and 4 °C, which was similar to winter duration under natural conditions. The pericarp of samaras facilitated germination at an early spring temperature (15/6 °C) after cold stratification at 1 and 4 °C, enabling the seedling survival of A. tegmentosum. We concluded that the covering structures composed of testa and pericarp in A. tegmentosum play vital roles in dormancy release and subsequent seed germination; they respond to external environmental cues based on the climatic conditions of Northeast Asia. This adaptation probably determines their behavior at an early life stage in response to environmental factors.