The effect of nitric oxide (NO) on antioxidant system and protective mechanism against oxidative stress under UV-B radiation was investigated in leaves of maize (Zea mays L.) seedlings during 3 days growth period. UV-B irradiation caused a decrease of leaf biomass including leaf length, width and weight during growth. Application of NO donor, sodium nitroprusside (SNP), significantly alleviated UV-B stress induced growth suppression. NO donor permitted the survival of more green leaf tissue preventing chlorophyll content reduction and of higher quantum yield for photosystem Ⅱ than in non-treated controls under UV-B stress, suggesting that NO has protective effect on chloroplast membrane in maize leaves. Flavonoids and anthocyanin, UV-B absorbing compounds, were significantly accumulated in the maize leaves upon UV-B exposure. Moreover, the increase of these compounds was intensified in the NO treated seedlings. UV-B treatment resulted in lipid peroxidation and induced accumulation of hydrogen peroxide (H2O2) in maize leaves, while NO donor prevented UV-B induced increase in the contents of malondialdehyde (MDA) and H2O2. These results demonstrate that NO serves as antioxidant agent able to scavenge H2O2 to protect plant cells from oxidative damage. The activities of two antioxidant enzymes that scavenge reactive oxygen species, catalase (CAT) and ascorbate peroxidase (APX) in maize leaves in the presence of NO donor under UV-B stress were higher than those under UV-B stress alone. Application of 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3- oxide (PTIO), a specific NO scavenger, to the maize leaves arrested NO donor mediated protective effect on leaf growth, photosynthetic pigment and free radical scavenging activity. However, PTIO had little effect on maize leaves under UV-B stress compared with that of UV-B stress alone. Nω -nitro-L-arginine (LNNA), an inhibitor of nitric oxide synthase (NOS), significantly increased H2O2 and MDA accumulation and decreased antioxidant enzyme activities in maize leaves under UV-B stress. This demonstrates that NOS inhibitor LNNA has opposite effects on oxidative resistance. From these results it is suggested that NO might act as a signal in activating active oxygen scavenging system that protects plants from oxidative stress induced by UV-B radiation and thus confer UV-B tolerance.

본 연구는 다양한 등숙기의 온도 및 일사량 조건에서 종실중 및 종실질소 함량 변화를 조사하여 등숙기 생육온도와 일사량이 벼 종실중 및 종실질소함량의 형성과정과 이들의 최종산물에 미치는 영향을 분석하고자 하였던 바 그 결과를 요약하면 다음과 같다. 1. 최종 종실중은 연차 및 품종에 관계없이 등숙기 일사량이 높을수록 큰 경향이었으며, 최종 종실중에 도달하는 출수일수는 짧아지는 경향이었다. 2. 종실 질소의 축적기간은 등숙기 적산일사량에 크게 영향을 받았으나 최종 종실질소함량은 큰 영향을 받지 않았다. 3. 유효적산온도(임계온도 7℃ )는 등숙기 생육온도에 관계없이 종실중 및 종실질소함량 변이를 잘 설명하였으나, 유효적산온도 또는 적산일사량에 따른 종실중 및 종실질소 함량은 등숙기 일사량간 변이가 매우 커 이들 단일 요인으로는 등숙기 일사량에 따른 종실중 및 종실질소함량 변이를 설명하는데 한계가 있었다. 4. 유효적산온도 및 적산일사량의 상승적은 등숙기 일사량에 관계없이 종실중 및 종실질소함량 변이를 잘 묘사하였다.

초대형 부체구조물은 파랑중 유탄성 변형이 심하게 발생하기 때문에 수평식 몰수평판과 같은 파랑에너지 흡수장치의 부가적인 개발이 요구된다. 본 연구에서는 몰수평판에 의해 야기되는 유체력 간섭현상이 폰툰형 부체구조물에 작용하는 라디에이션 유체력에 어떠한 영향을 미치는지 수치적인 해석을 통하여 그 특성을 파악하고자 한다. 폰툰형 부체구조물과 몰수평판의 상하운동에 의해 발생하는 라디에이션 유체력을 계산하기 위해 고정격자계와 이동격자계로 구성되는 중합격자법을 토대로 한 수치계산법을 개발한다. 또한 쇄파현상과 같은 비선형성이 강한 자유표면 문제를 해결하기 위하여 유한차분법을 적용하여 시뮬레이션을 실시하고 그 결과를 실험데이터와 비교함으로서 수치계산법의 신뢰성을 확인한다. 몰수평판에 의해 발생하는 유체력 간섭 영향의 특성을 분석하여 부체구조물의 파랑중 유탄성 변형에 미치는 그 효과에 대하여 논의한다.

The effect of UV on the mortality rate of toxic dinoflagellate Amphidinium carterae causing a red tide in the coastal area of south Korea was investigated in the batch and continuous-scale reactor equipped with ultraviolet irradiation-apparatus. Degussa P25 titanium oxide, a photocatalyst proved to be effective for the mortality of Amphidinium carterae supplied with photocatalyst and UV radiation were greater than 95% in 2 minutes of UV radiation and the rate were higher than that by UV-radiation without titanium dioxide in the batch and continuous-flow scale reactor. The mortality time of Amphidinium carterae increased with the cell density under UV-illumination in the batch scale reactor. The mortality rate in the density of 5.0×104 cells/mL at the same experimental condition was more than 90% in 4 minutes in the continuous flow scale reactor. The percentage of 99.9±0.1% of Amphidinium carterae in the density of 5.0×104 cells/mL was died in 20 minutes when the phytoplankton was illuminated with UV-radiation without photocatalyst.

The concerns on the crop damage by ultraviolet (UV) radiations is increasing owing to the decrease of their absorbing stratospheric ozone in the tropospheric. Cultivar differences on early growth of UV radiation among five Korean rice cultivars, four japonica types and one Tongil type (indica-japonica cross hybrid), were studied. Pot-seeded rice plants were grown under four different radiation conditions, i.e., visible radiation only, visible radiation with supplemented with high or low dose of UV-B (280~320 nm in wavelength) and UV-C (less than 280 nm in wavelength). The inhibitory degree on plant height, shoot and root weight and length of leaf blade and leaf sheath were determined at 40 days after seeding. UV-C showed the most severe inhibitory effect on the degree of biomass gain and leaf growth in most cultivars examined, followed by high UV-B and low UV-B. Among the cultivars used, the Kuemobyeo was the most sensitive cultivar and had not repair or showed resistance ability to continued irradiation of UV radiation. However, Janganbyeo and Jaekeon showed different responses that the elongation of leaf blades was promoted on 2nd and 3rd leaves and inhibited on 4th and 5th leaves but this inhibitory degree was reduced on 6 th and 7th leaves. Such tendency on leaf growth means that both cultivars had low sensitivity and most resistant ability to continued irradiation of UV radiation. While Tongil showed different response to enhanced UV radiation, ie., low UV-B promoted leaf growth but the inhibitory was severely increased by continued irradiation of high UV-B and UV-C, which means that Tongil had high threshold of UV radiation for response as an inhibitory light of plant growth. The results of this study indicate that the differences on sensitivity or resistant to the effects of UV radiation were existed among Korean rice cultivars