• 대한토목학회논문집
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• 제32권4C호
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• pp.169-175
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• 2012

불포화토의 함수특성은 구속효과 및 이력현상에 따라 변화한다. 이로 인하여 불포화 지층의 유효응력을 정의할 때, 모관흡수력이 기여하는 효과가 깊이에 따라 변화하거나 침투 및 증발과정에서 상이하게 나타난다. 불포화토의 유효응력은 흡수응력 특성곡선에 근거하여 일반화 할 수 있다. 이러한 일반화를 위해서, 구속응력과 함수특성곡선의 관계를 찾는 것이 필요하다. 본 연구에서는 다양한 구속응력을 가한 상태에서 압력판 추출시험을 수행하고 건조 및 습윤과정에서 나타나는 함수특성의 이력현상을 획득하였다. 그리고 각 이력과정에 대한 유효 체적함수비와 모관흡수력 관계를 구할 수 있었다. 이로부터 모관흡수력에 따른 흡수응력 특성곡선을 정의할 수 있었다. 또한 삼축시험시 구한 불포화 전단강도로부터, 흡수응력과 유효응력을 모관흡수력으로부터 구할 수 있었다. 함수특성에 근거한 유효응력 파괴규준은 유일하게 나타났으며 포화시 파괴포락선과 일치하였다. 삼축시험으로부터 구한 흡수응력은 대표 함수특성곡선으로부터 구한 것과 유사하게 나타났다. 따라서 각 이력과정에서 구속효과에 대하여 함수특성곡선이 유일하게 정의될 수 있음을 입증하였다.

• 한국환경과학회지
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• 제10권1호
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• pp.79-84
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• 2001

To assess resistance of transgenic tobacco plants which overexpress superoxide dismutase (SOD) and ascorbate peroxidase (APX) in chloroplasts to water stress, changes in leaf water potential, turgor potential, stomatal conductance and transpiration rate were measured. Leaf water potential in all plants remained high up to day 4 after withholding water but thereafter decreased markedly. In spite of a remarkable decrease in leaf water potential, some of transgenic plants maintained higher turgor potential compared with control plant on day 12. In particular, the transgenic plant expressing MnSOD showed an outstanding maintenance in turgor pressure by osmotic adjustment throughout the experiment, resulting in high stomatal conductance and transpiration rate. However, among transgenic plants, osmotic potential was reduced more effectively in multiple transformants such as the double transformant expressing both MnSOD and APX, and the triple transformant expressing CuznSOD, MnSOD and APX than single transformants. Consequently, further research is needed to get general agreement on the tolerance of transgenic plants to water stress at different growth stages for each transgenic plant.

• 한국환경과학회지
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• 제25권1호
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• pp.173-179
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• 2016

Leaf water and osmotic potential, chlorophyll content, photosynthetic rate, and electrolyte leakage were measured to evaluate tolerance to water stress in wild-type (WT) and transgenic tobacco plants (TR) expressing copper/zink superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) in chloroplasts. Leaf water potential of both WT and TR plants decreased similarly under water stress condition. However, leaf osmotic potential of TR plants more negatively decreased in the process of dehydration, compared with WT plants, suggesting osmotic adjustment. Stomatal conductance (Gs) in WT plants markedly decreased from the Day 4 after withholding water, while that in TR plants retained relatively high values. Relatively low chlorophyll content and photosynthetic rate under water stress were shown in WT plants since $4^{th}$ day after treatment. In particular, damage indicated by electrolyte leakage during water stress was higher in WT plants than in TR plants. On the other hand, SOD and APX activity was remarkably higher in TR plants. These results indicate that transgenic tobacco plants expressing copper/zink superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) in chloroplasts improve tolerance to water stress.

• Journal of Pharmaceutical Investigation
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• 제11권2호
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• pp.11-15
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• 1981

Antler, deer horn, occupies a particular place in oriental folk medicine as so called tonic remedy. In order to study on the effects of Antler water extract on stress resistance in mice, quantitative response was measured for the change of spontaneous activity by chemical stress drugs in the control group or the Antler water extract pretreated group. Spontaneous activity in mice was measured by counting the number of interruptions of light. The results of experiment were summerized as follows; I) In case of administrating Antler water extract 10mg/kg, 20mg/kg, 50mg/kg, and 100mg/kg, no significant change was observed in spontaneous activity in comparison with the control group. II) In case of administrating Antler water extract for 5 days or 10 days, no significant change was observed in spontaneous activity by chemical stress drugs, caffein and chloropromazine, in comparison with the control group.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.513-516
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• 2001

Water stress measurements of rice that use spectral reflection characteristics have been conducted to detect a water stress of rice during growing stage. Water stress reaction was measured using a spectroradiometer in the wavelength range from 300nm to 1100nm. In order to maintain all the experimental conditions, the measurement time have been settled at a fixed solar radiation times. Spectral reflectance were measured as a function of the moisture content. The results indicate that the spectral reflectance of rice was dependent on moisture content. As the moisture content is lowered the spectral reflectance of rice formed in NIR wavelength range increased. This effect can be best explained in terms of water stress.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.382-387
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• 1998

Triaxial compression tests were run to study on the undrained strength characteristics of fiber mixed kaolin clay(Hadong). The influence of various test parameters such as amount and aspect ratio(ratio of length to diameter) of fiber, confining stress was also investigated. Test results showed that the increase in aspect ratio was increased in deviator stress at failure, but no effect on pore water pressure at failure. Deviator stress at failure was also increased at 0.5％ mixing ratio(weight fraction of fiber to that of soil solid) of fiber but it was, thereafter, decreased and wits reached to constant after 2％ mixing ratio. On the contrary, Pore water pressure at failure was increased as mixing ratio of fiber was greater than 1%. Deviator stress and pore water pressure of both clay and fiber mixed clay(FMC) at failure were increased as confining stress was increased. Deviator stress of FMC at failure was about 10％ larger than that of clay, but pore water pressure of FMC at failure was almost similar to that of clay.

• The Plant Pathology Journal
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• 제27권3호
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• pp.249-256
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• 2011

Tall fescue (Schedonorus phoenix Scop.) is resistant to abiotic and biotic stresses through a symbiotic relationship with Neotyphodium coenophialum. However, this endophyte has been considered detrimental since it produces toxic alkaloids to animals. It is vital to understand mutuality between these two to maximize positive impact of the endophyte on agri-ecosystem. Little research has been conducted on endophyte transmission mechanism in planta. To provide basic information related to endophyte transmission, an experiment was conducted to examine the effect of endophyte genotype and water stress on endophyte transmission by imposing soil moisture deficits at different stages of panicle development. There was water stress effect on endophyte frequency but not on concentration, whereas endophyte genotype significantly influenced endophyte concentration in pseudostem of tall fescue at boot stage. Reproductive tillers showed greater endophyte frequency and concentration. Endophyte frequency in florets or seeds depended on position within panicle. There was no drought effect on endophyte concentration, but showed the effect of endophyte genotype on endophyte concentration in florets and seeds. Overall endophyte concentration in seeds was higher. From this study, we may conclude that although water stress reduced endophyte frequency in vegetative tiller, water stress does not have effect on endophyte transmission, suggesting that drought is not an important factor controlling the endophyte transmission from plant to seed. Endophyte genotype and seed position in a panicle affected endophyte transmission, indicating that these two factors are involved in endophyte transmission and may determine seed transmission of endophyte in tall fescue.

• Geomechanics and Engineering
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• 제22권5호
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• pp.375-384
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• 2020

In this study, the application of conventional cubic law to a deep depth condition was experimentally evaluated. Moreover, a modified equation for estimating the rock permeability at a deep depth was suggested using precise hydraulic tests and an effect analysis according to the vertical stress, pore water pressure and fracture roughness. The experimental apparatus which enabled the generation of high pore water pressure (< 10 MPa) and vertical stress (< 20 MPa) was manufactured, and the surface roughness of a cylindrical rock sample was quantitatively analyzed by means of 3D (three-dimensional) laser scanning. Experimental data of the injected pore water pressure and outflow rate obtained through the hydraulic test were applied to the cubic law equation, which was used to estimate the permeability of rock fracture. The rock permeability was estimated under various pressure (vertical stress and pore water pressure) and geometry (roughness) conditions. Finally, an empirical formula was proposed by considering nonlinear flow behavior; the formula can be applied to evaluations of changes of rock permeability levels in deep underground facility such as nuclear waste disposal repository with high vertical stress and pore water pressure levels.

• 한국작물학회지
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• 제40권5호
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• pp.594-599
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• 1995

검정콩 1호를 공시품종으로 하여 콩의 영양생장기에 15일간 습해처리하고 그에 따른 엽생장 및 지하부의 생리적 반응을 조사한 결과는 다음과 같다. 1. 습해처리기간중 근류는 심토층에서부터 사멸되기 시작하였으며 습해기간이 7일 이상 지속될 경우 전체 근류의 35%이상이 사멸되었다. 2. 습해를 받으면 근류의 Bacteroid층이 균열되기 시작하였으며 습해기간이 지속될 경우 균열 양상은 더욱 심화되었다. 3. 습해기간중 토심 5cm이하에 분포한 뿌리활력은 무처리에 비해 크게 감소하였으며 표토층에 분포한 뿌리는 큰 변화가 없었다. 4. 7일간의 습해처리로 주근의 외피조직 및 유관속조직의 분리현상과 일부 파괴현상이 관찰되었다. 5. 습해처리 기간 중의 엽면적 생장은 정상식물체의 엽면적 생장의 절반에 불과하였다.

• 생물환경조절학회지
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• 제17권4호
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• pp.273-282
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• 2008

수분 공급을 제한하여 수분 부족 스트레스를 처리한 상추식물에서 산화적 스트레스와 관련된 monodehydroascorbate reductase (MDHAR)의 활성도, 엽록소 함량, 과산화수소의 함량 등과의 상관관계를 조사한 결과, 생육배지의 수분의 함량이 감소함에 따라 식물체내 과산화수소의 생성량이 증가($R^2$=0.8851)하였으며, 수용성단백질 함량은 점차 감소($R^2$=0.9826)하는 경향을 나타내었다. 총 엽록소함량은 수분 부족 스트레스를 처리한 공시작물에서의 함량이 정상 생육시 보다 그 함량이 대체적으로 낮은 경향을 보였으며, 엽록소 a와 엽록소 b함량 변화도 총 엽록소의 함량변화와 비슷한 경향을 보였다. 그러나 총 엽록소에 대한 카로티노이드의 비율은 수분 부족 스트레스를 처리한 식물에서 정상생육 시 보다 더 높은 경향을 보였다. 수분 부족 스트레스가 진행됨에 따라 아스코브산의 함량은 정상 생육 시 보다 더 높은 경향을 보였으나 환원형인 디하이드로아스코브산의 함량은 수분 부족 스트레스를 처리한 초기에 정상생육 시 보다 더 낮은 경향을 보였다. MDHAR의 활성도는 사이토졸(cytosolic) 분획과 엽록체(chloroplastic) 분획에서 공히 크게 증가하였으며 MDHAR의 mRNA 전사 정도도 수분 부족 스트레스가 진행됨에 따라 크게 증가하였다. 수분함량이 감소함에 따라 MDHAR의 활성도가 크게 증가하였으며, 또한 과산화수소의 함량이 증가함에 따라서도 MDHAR의 활성도가 크게 증가($R^2$=0.9937과 0.8645)되어 수분 부족 스트레스로 나타나는 요인들과 MDHAR 사이에 밀접한 관련이 있음을 확인할 수 있었다.