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.

Prunus spachiana (Lavallée ex Ed.Otto) Kitam. f. ascendens (Makino) Kitam leaves exert natural anti-inflammatory effects by inhibiting nitric oxide formation. P. spachiana flowers bloom earlier than other Prunus spp. and thus could serve as a valuable resource for the horticulture and pharmaceutical industries. However, its seed dormancy class and germination traits remain uncharacterized. Thus, this study aimed to characterize the seed dormancy and germination of P. spachiana. Imbibition, phenological, and move-along experiments were performed, and the effects of H₂SO₄ treatment, hormone soaking, warm/cold stratification, and endocarp removal on germination were explored. Observation revealed that ripe seeds of P. spachiana contain developed embryos and are water permeable. Radicle and shoot emergence began in March and April, respectively, under natural conditions in the year following production. No seed germination was observed after 30 days of incubation at 4, 15/6, 20/10, or 25/15 °C under light/dark conditions, indicating the physiological dormancy of the seeds. Germination increased with prolonged stratification and was affected by incubation temperature. Seed scarification by H₂SO₄ and soaking with gibberellic acid (GA₃) and fluridone were ineffective in breaking dormancy. However, GA₃ soaking of the seeds after endocarp removal effectively induced germination (100%). These results indicate that P. spachiana seeds exhibit intermediate physiological dormancy.

This study was conducted to examine the effect of plant growth regulators on the rooting and growth of Rhododendron micranthum Turcz., a rare plant in South Korea. Indole-3-butyric acid (IBA) 150, 250, 350 mg·L⁻¹ and α-naphthaleneacetic acid (NAA) 50, 150, 250 mg·L⁻¹ treatment groups were established and cutting was performed in a commercial growth medium in March 2021 with 3 replications of 10 plants per group. After 70 days, the longest initial root growth was observed under the NAA 150 and 250 mg·L⁻¹ treatments. Moreover, the number of roots and percentage of rooting were slightly higher in NAA 150 and 250 mg·L⁻¹, indicating that these treatments were more effective in promoting plant growth. The above-ground part of plants treated with NAA 150 and 250 mg·L⁻¹ had a taller plant height, longer and wider leaves, and a greater number of leaves compared to other groups. Accordingly, the survival rate of plants treated with NAA 150 and 250 mg·L⁻¹ was higher than 80%, suggesting well-established roots and excellent above-ground growth. Therefore, treatment with growth regulator NAA at 150 and 250 mg·L⁻¹ is considered beneficial for the cutting of R. micranthum Turcz.

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.

Orostachys margaritifolia Y. N. Lee (OMY) is an endemic Korean plant in the family Crassulaceae that is known to contain a variety of bioactive compounds. To assess the physiological activities of an OMY ethanol extract, ABTS⁺ and DPPH radical scavenging assays and a nitric oxide (NO) inhibition assay were conducted. The phytochemical makeup of the extract was profiled via liquid chromatography-mass spectrometry (LC-ESI/MS) and high-performance liquid chromatography with a photodiode array detector (HPLC/PDA). The OMY extract was found to have weaker ABTS⁺ and DPPH radical scavenging activities than the control group (green tea). In the NO inhibition assay, the OMY extract induced a significant increase in macrophage cell viability but showed a lower NO inhibitory activity than l-NAME, producing an IC₅₀ value of 202.6 μg/mL. The LC-ESI/MS and HPLC/PDA analyses identified isoquercitrin and astragalin in the OMY extract, quantifying their contents at 3.74 mg/g and 3.19 mg/g, respectively. The study revealed possibilities for the utilization of OMY as a future source of drugs for alleviating inflammation and diseases related to reactive oxygen species.