Hibiscus hamabo, called "Hwang-geun", growing about 3m in height is a deciduous shrub or subtree of Malvaceae. Because the number of these species is very limited in the world, the Ministry of Environment has designated H. hamabo as a preserved plant. The Korea Forest Service also protects it strictly by law since H. hamabo is an out-of-the-way plant and possibly may be exterminated soon in Korea. Investigation for distribution and ecological characteristics of the habitat for H. hamabo was carried out on Soan Island. Two wild H. hamabo were found at the forest edge (34。11‘35.4“N, 126。38'55.9"E) along the sea coast located in the southern part of Soan Island and this was the first report in the Korean academic world. These two wild H. hamabos were growing in a naturally inhibited area. The diameters at the base were 12cm and 15cm. The Tree heights were 150cm and 210cm and the number of branches of each wild H. hamabo was 4 and 7. However, the present condition of these plants was not good. Environmental conditions of the naturally inhibited area of H. hamabo were very mild because it is located at the edge of the forest and is always sunny during the daytime since the slope of the inhibited area is facing South. The ground drained very well since the soil was made of gravels and sand. Because the percent of vegetation of the subtree layer where H. hamabo was growing was 40%, the cover degree and sociability of Ilex crenata trees and Eurya japonica were found to be high. In the naturally inhibited area of H. hamabo, a dominant value of Rubus parvifolius in the lower part of the herb layer was very high and many plants in Compositae, such as Artemisia princeps var. orientalis and Erigeron annuus, were also present. A dominant value of liana, such as Vitis thunbergii var. sinuata, Rosa multiflora, Clematis terniflora and Hedera rhombea, and Gramineae plants that rhizomes were well developed and aggressively propagated, such as Miscanthus sinensis var. purpurascens, Phragmites communis, Spodiopogon cotulifer and Oplismenus undulatifolius which were surveyed as high, too. These results imply that H. hamabo might be exterminated soon through a natural selection if the proper management of the naturally inhibited area of H. hamabo is not conducted continually.

In order to determine the optimum harvest time for the seed production of inbreds and hybrids in silage corn, the ears of sib-pollinated 'KS5', 'KS7rhm', and 'Ga209' and cross-pollinated 'KS5' ~times 'KS6' (Suwon19), 'KS7 rhm' ~times 'KSl17' (Suwonok), and 'Ga209' ~times 'DB544'(Kwanganok) were harvested at the one-week intervals from 4 to 10 weeks after silking. The optimum harvest time for the seed production for 'KS5', 'KS5' ~times 'KS6', 'KS7 rhm', and 'KS7rhm' ~times 'KS117' was 7 weeks after silking considering both emergence rate and plumule growth in cold test. Although earlier harvested seeds showed similar germination rate as the seeds harvested at the optimum time at 25~circC , their emergence rate were lower in cold test. Seed weight and α -amylase activity of earlier harvested seeds were lower compared to those of seeds harvested at the optimum time, while leakage of total sugars and electrolytes were higher. However, the later harvested seeds showed lower germination rates at 25~circC and emergence rates in cold test probably due to the lower α -amylase activity although they showed increased seed weight and reduced leakage of total sugars and electrolytes. In contrast, the emergence rate of 'Ga209' and 'Ga209' ~times 'DB544' in cold test increased up to 10 weeks after silking probably due to the increased seed weight and α -amylase activity and reduced sugar and electrolyte leakages during the germination. The cross-pollinated F1 hybrid seeds showed higher germination and emergence rates at 25~circC and in cold test, and higher plumule growth and α -amylase activity compared to those of sib-pollinated inbreds.