Su Gwang Lee’s scientific contributions

Lespedeza species are mainly used for wildlife food and cover and for erosion control. The germination of these species can be enhanced after a fire occurrence in forest, which is known as fire-activated seeds to germinate. While the heat treatment could break seed dormancy of Lespedeza, its germination rate was quite low. We investigated that chemical scarification could promote germination of L. tomentosa. Seeds were soaked in 100% sulfuric acid (H₂SO₄) for 0, 1, 3, 6, 12, 24, 48, 96, 192, and 384 min, and then washed in distilled water for 24 h. Very few seeds were germinated in control (H₂SO₄ for 0 min). More than 90% of seeds were germinated in H₂SO₄ for 24, 48, and 92 min. However, some damage was observed in roots and cotyledons of seedling dipped in H₂SO₄ for a long time. To search the optimal soaking time in H₂SO₄ without defects, seeds scarified inH₂SO₄ for 30, 60, 90, 120, 150, 180, and 300 min were sown the commercial soil medium. Seeds treated with H₂SO₄ for 90 min and 150 min emerged by about 92% and 84%, respectively. Therefore, H₂SO₄ treatment could break the seed dormancy of Lespedeza species, and especially in case of L. tomentosa the optimal treatment time in sulfuric acid was one to two hours. Germination of L. tomentosa began promptly following the scarification and was completed within about one month, indicating that seeds has no physiological dormancy, just has physical dormancy.

This study was conducted to determine the effects of seed storage method (-20^{\circ}C, 2^{\circ}C dry, 2^{\circ}C wet 30 days, 2^{\circ}C wet 60 days, stratification and room temperature) and shading treatment(control, 50%, 80%) on seed germination, seedling growth of endangered species, Iris dichotoma and Iris setosa. As a result, seed germination rate of I. dichotoma was the highest at 75% when seed were stored at 2^{\circ}C wet 60 days and then sown under non-shading condition. The seed of I. dichotoma belong to intermediate seed. Seed germination rate of I. setosa was the highest at 95% when seed were stored at 2^{\circ}C wet 60 days and then sown under 80% shading condition. The seed of I. setosa belong to recalcitrant seed. Seedlings of I. dichotoma and I. setosa showed not only the best seedling quality but also seedling vigor index in seed stored at 2^{\circ}C wet 60 days under non-shading condition, with the growth characteristics of plant height (6.4, 7.2 cm), number of leaves (3, 4), leaf width (4.6, 3.2 mm), leaf length (5.7, 6.8 cm), fresh weight (aerial/root part; 144/260, 97/153 mg), dry weight (aerial/root; 31/20, 17/17 mg) and seedling vigor index and modified seedling vigor index (13,895/9,479, 13,256/8,668). In this research, I. dichotoma and I. setosa seed were stored at 2^{\circ}C wet 60 days, and then sown in non-shading condition, seed germination rate was more than 75%, 90%, respectively, and production of superior quality seedlings.

This study was carried out to determine the effects of seed storage methods and pre-treatments on seed germination, soil types and shading conditions on potted seedlings growth of S. sieboldiana var. pendula and S. sieboldiana for. xanthocarpa, endemic species in Korea. The seed germination rate of S. sieboldiana var. pendula was the highest at 48.6% when seeds were treated with stratification for 60 days and then soaked in 100 ppm GA_3. And seed germination rate of S. sieboldiana for. xanthocarpa was the highest at 51.4% when seeds were pre-chilled for 30 days and then soaked in 100 ppm GA_3. And potted seedlings of S. sieboldiana var. pendula showed the best quality under 50% shading in bedsoil with the growth characteristics of plant height (41 cm), number of leaves(8), leaf width (16 cm), leaf length (18 cm), root length (22 cm), fresh weight(aerial part/root part; 20/6.9 g) and dry weight(aerial part/root part; 4.5/2.0 g). And potted seedlings of S. sieboldiana for. xanthocarpa showed the best quality under non-shading in bedsoil with the growth characteristics of plant height (39 cm), number of leaves(10), leaf width (12 cm), leaf length (15 cm), root length (22 cm), fresh weight (aerial part/root part; 21/13 g) and dry weight (aerial part/root part; 4.2/2.2 g). Therefore, seeds treated with stratification or prechilling and then soaked in GA_3 were effective in germination of S. sieboldiana var. pendula and S. sieboldiana for. xanthocarpa, and potted seedlings should be cultivated in bedsoil under non or 50% shading condition.

This study was conducted to determine the effects of seed storage methods (-20^{\circ}C, stratification, 2^{\circ}C dry, 2^{\circ}C wet and room temperature) and GA_3 application (control, dH_2O, 10, 100, 1000 ppm) on seed germination and seedling growth of S. lyratum. As a result seed germination rate of S. lyratum was the highest at 91% when seeds were stored at room temperature and then soaked for 24 hours in GA_3 10 ppm. And seedlings of S. lyratum showed the best quality when seed were stored at 2^{\circ}C dry and then soaked for 24 hours in GA_3 1000 ppm, with the growth characteristics of plant height (47 mm), number of leaves (8), leaf width (12 mm), leaf length (19 mm), fresh weight (aerial/root part; 471/476 mg), dry weight (aerial/root; 106/41 mg) and seedling quality indices (106). Therefore, S. lyratum seed were stored at 2^{\circ}C dry, and then soaked for 24 hours in GA_3 1000 ppm, seed germination rate was more than 80% and production of superior quality container seedlings.

This study was carried out to investigated the effects of soil type and light condition on seedling quality of rare and endemic plants Orostachys iwarenge and Orostachys iwarenge for. magnus. The best seedling quality of O. iwarenge and O. iwarenge for. magnus seedling were shown in Klasmann soil at non-shading or LED (Red+Blue) condition, 50% shading or LED (Red+Blue) condition, respectively. Survival of O. iwarenge seedling was not influenced by the period of experiment but survival of O. iwarenge for. magnus seedling in sandy soil conditions decreased significantly. Results of correlation analysis of seedling quality and survival rate, indicated that O. iwarenge showed a correlation of 0.8 or more at plant height, leaf length and fresh weight. O. iwarenge for. magnus showed a correlation of 0.8 or more at plant height, leaf width and leaf length. Especially, seedling survival of O. iwarenge and O. iwarenge for. magnus showed a correlation of 0.8 or more at first seedling survival and second seedling survival. It was important to manage the early seedling stages of O. iwarenge and O. iwarenge for. magnus. Therefore, seedlings with plant height (over 2.5~4 cm) and root length (over 3~5 cm) were grown vigorously at 35 days after the seedling was transplanted in mid-April in Klasmann soil of 72 plug cell tray at LED (Red+Blue) conditions.

This study was conducted to determine the effects of seed storage temperature and pre-treatment on seed germination, seedling quality and vigor index of wild Trichosanthes kirilowii and Trichosanthes kirilowii var. japonica. As a result the highest germination rate of T. kirilowii was the 95% at seed stored in room temperature and then soaking for 24 hours in . And the highest germination rate of T. kirilowii var. japonica was 96% at seed stored in and then soaking for 24 hours in (100 ppm). But the seed germination rate was non-significance in pre-treatment at seed stored in room temperature . Seedlings of T. kirilowii and T. kirilowii var. japonica showed not only the best seedling quality but also seedling vigor index in seed stored at and then soaking for 24 hours in (100 ppm). In this research, T. kirilowii and T. kirilowii var. japonica seed were stored in room temperature or , and then sown in peat moss, seed germination rate was more than 90% and production of superior quality seedlings.

This study was conducted to determine the effects of rice hull cover on seed germination and tray types, soil types, shading conditions for seedling growth of Codonopsis pilosuala. We also examined the feasibility of cultivation of small seedlings transplanted in the Gyeonggi-do area for a month. Under control condition, the seed germination was 8% whereas it dramatically increased to 78% under rice hull cover treatment. Under the different conditions (tray types, soil types, and shading conditions), young seedlings showed the best quality without shading in TKS soil of 50 plug cell tray, with the growth characteristics of plant height (11.9 cm), number of leaves (71), leaf width (3.1 cm), leaf length (2.6 cm), and root length (14.3 cm). Seedling quality was the best without any shading in TKS+perlite, with the physiological characteristics of evaporation (3.9 mmol{\cdot}m^{-2}s^{-1}), carbon assimilation (9.1 ?mol{\cdot}m^{-2}s^{-1}), and water use efficiency (2.2 ?mol{\cdot}m^{-2}s^{-1}). Considering the economical, morphological, physiological and survival rate of the seedlings, it was an ideal method for transplanting seedlings in the field after they have been grown for 30-45 days in TKS and TKS+perlite of 200 plug cell tray in 0% or 30% shaded conditions. As the results of 5 months examination on the possibility to cultivate Codonopsis pilosuala in the Gyeonggi-do area, 88% to 96% of survival rate was observed with normal induced flowers. Therefore, cultivation of Codonopsis pilosuala was possible in the Gyeonggi-do area. While there were symptoms of etiolation and wilting under no shading condition, they did not appear in 30% and 70% shading conditions. Therefore, cultivation of Codonopsis pilosuala is considered to be necessary 30% or 70% shading.

The present study was examined seed germination and growth characteristics of Cynanchum wilfordii under the following conditions such as soaking temperature, concentrations of , trays and soil types, and shading conditions. In seed pre-treatment, germination rate was the highest at 93% when soaked in 100 ppm at and seedling growth was best in 50 plug cell tray. Physiological quality was best in the condition in which seeds were treated with 10 ppm at . Taking into consideration the seedling growth, their physiological quality as well as economical aspects, seedlings with plant height (over 10 cm) and root length (over 10 cm) were grown vigorously 30-45 days after the seeds were sown in mid-April in TKS, TKS+perlite and TKS+rice hull of 128 or 200 plug cell tray.

To obtain biological basic data for the conservation strategies establishment of a rare mistletoe species, Loranthus tanakae(Loranthaceae) in Korea, the distribution range, habitat characteristics and an assessment of the conservation status on the natural populations of L. tanakae were investigated. As a result, the natural populations of L. tanakae were distributed in Bakdudaegan from Mt. Chiri to Mt Seorak in Korea penninsula, and 97.8% of surveyed individuals of the mistletoe species were found in Gangwon province. In natural populations, 1,385 individuals of L. tanakae were parasitic on 480 host trees, and distributed in sunshiny ridges of mountains of altitude range of 353 m to 1,250 m. The range of host trees of L. tanakae were composed of 5 families, 6 genera, 9 species, 1 subspecies, and of these, Quercus mongolica was preferred with 81.5% (389 trees among 480 host trees). As a result of assessing the conservation status through IUCN, L. tanakae was evaluated as Vulnerable (VU). It was considered that Mt. Seorak, Mt. Taegi and Mt. Odae population as habitats with the highest density of distribution of natural populations of L. tanakae should be designated as the protected areas. Thus, conservation strategies and related methods of the natural populations of L. tanakae were also discussed for the sustainable conservation.