Global warming means not only increase in average air temperature but also increase in frequency of extreme weathers such as extremely high temperature over 45oC. Crops are generally sensitive to high temperature during their reproductive growth stage. This experiment was thus conducted to investgate physiological responses of rice (Oryza sativa cv. Chucheong) and soybean (Glycine max cv. Sinpaldal) to high temperature (HT) stress at their reproductive stage. Rice and soybean were exposed to different degrees of high temperature stress by keeping them in a growth cabinet deisnged to maintain air temperature up to 45oC for at least 5 hours in a day for different durations, 0, 1, 2, 3, and 4 days. HT stress treatment delayed heading and flowering of rice and increased the sterility of its' main panicle with increasing duration of HT treatment; 19.7 43.4, 68.1, 81.5 and 91.1% at 0, 1, 2, 3 and 4 days HT treatment, respectively. Increasing sterility due to HT treatment thus resulted in significant rice yield loss; 5.07 4.27, 4.32, 4.51 and 3.62 g/plant at 0, 1, 2, 3 and 4 days of HT treatment, respectively. Soybean was also significantly affected by HT stress in its pod formation and sterility, particularly along the vertical stem. Increasing pod sterility with increasing HT treatemnt thus resulted in significant soybean yield loss.

Miscanthus, a perennial rhizomatous C4 grass, is a potential biomass crop. Its propagation can be made by seed, rhizome and cultured tissue. Propagation by rhizomes or cultured tissues is expensive, while seed propagation is rather simple and cheaper. However, little effort has been made to investigate seed germination, particularly in relation with exogeneous chemicals including plant growth regulators to improve germination. This study was conducted to improve the seed germination of Miscanthus with GA3, NaClO, KNO3 and procloraz. iscanthus sacchariflorus and Miscanthus sinesis seeds were treated with the above chemicals at different concentrations. Decoated seeds were soaked in GA3, NaClO, KNO3, and procloraz solutions. Pretreated 20 Miscanthus seeds were then sown in each petri dish covered with a single layer of Watman filter paper and maintained in the incubation chamber at 33℃/25℃ (day/night). Seed germination were measured every 8 hours. As a result, the best germination was obtained at 250 mg/L GA3, 0.3% NaClO, 1 mM KNO3 and 1 mL/L procloraz solutions.

Acid rain due to air pollution has been believed to be harmful to vegetation and crops, either by direct deposition on the foliage or by indirect leaching of nutrients from the soil. This study was conducted to investigate physiological response and damage of soybean caused by acid rain in the glasshouse at the experimental station of Seoul National University. Soybean (Glycine max L.) cv. Sinpaldal was subjected to simulated acid rain (SAR) two times a week from R2 stage until its maturity. The pH values of SAR treatments were ranged from 2 to 5 together with tap water treatment (pH 7±0.2) as a control. The SAR was composed of H2SO4 and HNO3 at the ratio of 2:1 (v/v). SAR treatment at pH 2 caused clear visual damage on leaves and pods with severe chlorosis and necrosis even after the first SAR was applied, while those at pH greater than 3 showed no clear visual damage. Chlorophyll content (expressed as SPAD value) tended to decrease with decreasing pH with significant reduction at pH 2 as compared with pH values greater than 3. Photosynthesis also showed decrease with decreasing pH with significant reduction at pH 3 and 2. Soybean yield and its components were also affected by SAR treatment, particularly significant at pH 2.