• Title/Summary/Keyword: Water stress

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Effects of Water Stress on Leaf Water Potential, Photosynthesis and Root Development in Tobacco Plant (수분 스트레스가 담배의 잎 수분 포텐셜, 광합성 및 뿌리발달에 미치는 영향)

  • 이상각;서용원;존슨 제리;강병화
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.42 no.2
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    • pp.146-152
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    • 1997
  • Development of shoot and root, leaf water potential and photosynthetic rate affected by water stress in early growing stage of tobacco were surveyed to interpret stress response in terms of plant physiological and agricultural aspects. The growth of shoot and root was highly suppressed by water stress and the difference in dry weight by rewatering was smaller in root than in shoot. The total root length was highly decreased by water stress and the lengths of root for water stress and non-stress were 74m and 84m, respectively, after rewatering. The root growth treated by water stress was increased between 2nd and 3rd day after treatment indicating that temporary water stress at early growing stage might have increased of root zone activity for early growth stage. The leaf water potentials were decreased to -7.63MPa, -9.47MPa, -11.89MPa, -13MPa at the 2nd, 3rd, 4th and 5th day by water stress. The relative water contents were 75%, 62% and 57% at the 3rd, 4th and 5th day after treatment. Photosynthesis was reduced largely by water stress. The photosynthetic rate after treatment at 2nd day and 3rd day was dropped to 18.15$\mu$mol. $CO_2$/$m^2$ㆍsec$^{-1}$ and 9.35$\mu$mol. $CO_2$/$m^2$ㆍsec$^{-1}$. It was never recovered to the normal, even after rewatering. Stomatal conductance had been reduced since 2nd day after treatment and increased after rewatering.

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Ecohydrologic Analysis on Soil Water and Plant Water Stress : Focus on Derivation and Application of Stochastic Model (토양수분과 식생의 물 압박에 대한 생태수문학적 해석 : 추계학적 모형의 유도와 적용을 중심으로)

  • Han, Suhee;Kim, Sangdan
    • Journal of Korean Society on Water Environment
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    • v.24 no.1
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    • pp.99-106
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    • 2008
  • With globally increasing interests in climate-soil-vegetation system, a new stochastic model of soil water and plant water stress is derived for better understanding of the soil water and plant water stress dynamics and their role in water-controlled ecosystem. The steady-state assumption is used for simplifying the equations. The derived model is simple yet realistic that it can account for the essential features of the system. The model represents the general characteristics of rainfall, soil, and vegetation; i.e. the soil moisture constitutes the decrease form of the steady-state and the plant water stress becomes increasing with the steady state when the rainfall is decreased. With this model, further deep study for the effects of soil water and plant water stress on the system will be accomplished.

A Study on the Stress Distribution of Steel Water Pipes(II) - Characteristics of Stress Distribution by External Forces and PWHT - (상수도용 도복장간관의 용접 및 외부하중에 의한 응력 특성에 관한 연구(II) - 복합외부하중 및 후열처리에 따른 용접부의 응력분포 특성 -)

  • 윤석환;이승기;나석주;고명환
    • Journal of Welding and Joining
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    • v.19 no.3
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    • pp.292-297
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    • 2001
  • One of the major characteristics that affects the life of welded steel water pipes is the stress distribution caused by welding and external forces. Some studios have bean carried out on the residual stress of steel water pipes. But the results on the stress distributions by welding and complex external forces are rare, because real water pipes operate under the ground and many kinds of external forces act simultaneously on the joints. To understand the complex stress distributions of welded joints, therefore predictions by numerical or analytic methods are required. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Based on these results, stress distributions by welding and complex external forces are evaluated by adopting the same numerical method. The influence of some post weld heat treatments on residual stress distributions is also investigated.

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Effect of Delayed Transplanting plus Water Stress on the Growth and Yield of the Rice Plants (한발로 인한 벼의 이앙지연 및 수분결핍장애가 생육 및 수량에 미치는 영향)

  • 권용운;소창호;권순국
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.28 no.3
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    • pp.79-88
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    • 1986
  • Drought occurs most frequently and severely around transplanting season of the rice plants in Korea. Shortage of water due to drought for the paddy fields often delays transplanting, and less often the rice plants are subjected to water stress after delayed transplanting. The present study aimed at quantification of the rice crop loss due to delayed transplanting, different inten3ity of water stress, and the combined effect of delay in transplanting followed by water stress for better use of limited water for irrigation under drought. The rice variety Chucheong, a japonica, and Nampung, an indica x japonica, were grown, transplanted to 1/200 a plastic pots, and subjected to different timing of transplanting and degree of water stress under a rainfall autosersing, sliding clear plastic roof facility with completely randomized arrangement of 5 replications. The results obtained are summarized as follows: 1.Twelve days or 22 days delay in transplanting without water stress reduced rice yield by 25% and 43% in the japonica variety, and by 15% and 60% in the indica x japonica variety. 2.The 10 days or 20 days water stress developed without irrigation after drainage in the rice plants transplanted at proper time lowered the water potential at the paddy soil 10cm deep to -4 bar, and -12 bar and caused rice yield reduction by 14%, and 45% in the japonica variety and by 8%, and 50% in the indica X japonica variety. 3.The 12 days delay in transplanting and 10 days or 20 days water stress reduced rice yield by 39% and 59% in the japonica variety, and by 38% and 52% in the indica x japonica variety. The 22 days delay in transplanting plus 10 days water stress caused yield reduction by 76%, i.e. meaningless yield, in both varieties. 4.The intermittent irrigation just to wet the soil body for 10 days after 10 days water stress without irrigation increased rece yield by 12 to 16% compared to the rice plants water stessed without irrigation continuously for 20 days in both varieties respectively. 5.The above results suggest strongly 1) to transplant the rice plants at proper .time even with some water stress rather than delay for sufficient water from later rainfall, and 2) to distribute insufficient irrigation water to broader area of transplanted rice with limited irrigation for better use of limited irrigation water. A greater sensitivity of japonica variety to a moderate water stress than the indica X japonica variety during initial rooting and tillering stage was noticed. To cope with frequent drought in rice culture, firstly the lasting time of transplanting without yield reduction should be clarified by region and variety, and secondly a scheme of rational distribution of limited water should be developed by region with better knowledge on the varietal distribution of limited water should be developed by region with better knowledge on the varietal responses to varying intensity of water stress.

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Short-range sensing for fruit tree water stress detection and monitoring in orchards: a review

  • Sumaiya Islam;Md Nasim Reza;Shahriar Ahmed;Md Shaha Nur Kabir;Sun-Ok Chung;Heetae Kim
    • Korean Journal of Agricultural Science
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    • v.50 no.4
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    • pp.883-902
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    • 2023
  • Water is critical to the health and productivity of fruit trees. Efficient monitoring of water stress is essential for optimizing irrigation practices and ensuring sustainable fruit production. Short-range sensing can be reliable, rapid, inexpensive, and used for applications based on well-developed and validated algorithms. This paper reviews the recent advancement in fruit tree water stress detection via short-range sensing, which can be used for irrigation scheduling in orchards. Thermal imagery, near-infrared, and shortwave infrared methods are widely used for crop water stress detection. This review also presents research demonstrating the efficacy of short-range sensing in detecting water stress indicators in different fruit tree species. These indicators include changes in leaf temperature, stomatal conductance, chlorophyll content, and canopy reflectance. Short-range sensing enables precision irrigation strategies by utilizing real-time data to customize water applications for individual fruit trees or specific orchard areas. This approach leads to benefits, such as water conservation, optimized resource utilization, and improved fruit quality and yield. Short-range sensing shows great promise for potentially changing water stress monitoring in fruit trees. It could become a useful tool for effective fruit tree water stress management through continued research and development.

A Study on the Stress Distribution of Steel Water Pipes(I) - Characteristics of Residual Stress Distribution by PWHT - (상수도용 도복장강관의 용접 및 외부하중에 의한 응력 특성에 관한 연구(I) - 후열처리에 의한 용접부의 잔류응력 특성 -)

  • 윤석환;이승기;나석주;고명환
    • Journal of Welding and Joining
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    • v.19 no.3
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    • pp.285-291
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    • 2001
  • Large steel water pipes are joined prevalently by the bell end method, and are welded both at inside and outside of lapped parts. In practice, welded joints of water pipes are very critical, because in most cases failure of pipes causing leakage occurs at the welded joint. Therefore some methods have been developed to ensure the soundness of welded joints of water pipes, like leakage tests and nondestructive tests (NDTs). But one of the major characteristics that affects the soundness of welded Joints is the stress distribution caused by welding and external forces. Some studies have been carried out on the residual stress of steel water popes, but complex stress distributions by welding and external forces are rarely studied. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Also, stress values are measured from real steel water pipes by the hole-drilling methods, and compared with predicted ones. The influence of some typical post weld treatments on residual stress distribution was also investigated by residual stress measurements.

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Experimental study on seepage characteristics of large size rock specimens under three-dimensional stress

  • Sun, Wenbin;Xue, Yanchao;Yin, Liming;Zhang, Junming
    • Geomechanics and Engineering
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    • v.18 no.6
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    • pp.567-574
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    • 2019
  • In order to study the effect of stress and water pressure on the permeability of fractured rock mass under three-dimensional stress conditions, a single fracture triaxial stress-seepage coupling model was established; By using the stress-seepage coupling true triaxial test system, large-scale rock specimens were taken as the research object to carry out the coupling test of stress and seepage, the fitting formula of permeability coefficient was obtained. The influence of three-dimensional stress and water pressure on the permeability coefficient of fractured rock mass was discussed. The results show that the three-dimensional stress and water pressure have a significant effect on the fracture permeability coefficient, showing a negative exponential relationship. Under certain water pressure conditions, the permeability coefficient decreases with the increase of the three-dimensional stress, and the normal principal stress plays a dominant role in the permeability. Under certain stress conditions, the permeability coefficient increases when the water pressure increases. Further analysis shows that when the gob floor rock mass is changed from high stress to unloading state, the seepage characteristics of the cracked channels will be evidently strengthened.

Stochastic Behavior of Plant Water Stress Index and the Impact of Climate Change (식생 물 부족 지수의 추계학적 거동과 기후변화가 그에 미치는 영향)

  • Han, Suhee;Yoo, Gayoung;Kim, Sangdan
    • Journal of Korean Society on Water Environment
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    • v.25 no.4
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    • pp.507-514
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    • 2009
  • In this study, a dynamic modeling scheme is presented to describe the probabilistic structure of soil water and plant water stress index under stochastic precipitation conditions. The proposed model has the form of the Fokker-Planck equation, and its applicability as a model for the probabilistic evolution of the soil water and plant water stress index is investigated under a climate change scenario. The simulation results of soil water confirm that the proposed soil water model can properly reproduce the observations and show that the soil water behaves with consistent cycle based on the precipitation pattern. The simulation results of plant water stress index show two different PDF patterns according to the precipitation. The simple impact assessment of climate change to soil water and plant water stress is discussed with Korean Meteorological Administration regional climate model.

Effects of Water Stress at Anthesis on the Growth and Grain Maturation in Barley (대맥 개화기의 수분부족이 생장 및 등숙에 미치는 영향)

  • 최원열
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.25 no.3
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    • pp.9-14
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    • 1980
  • This experiment was carried out to examine the effect of water stress at anthesis on the grain maturation and to interpret the immediate and resulting growth response in barley. The dry weight of root, stem, internode, flag leaf and grain under water stress was remarkably more reduced than that under no-water stress, respectively. Water stressed plants had heavier grain dry weight during 7.14 days after water stress than that under no-water stress, but this early response was reversed significantly in the later period. The relative turgidity of organs except grain under water stress was severely lowered than that under no-water stress. The net photosynthsis by rewatering after water stress had been kept at the lower level than that under no-water stress ti1l the late maturation.

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Lubrication Characteristics of Condensed Water Molecules at Solid Surface through Molecular Simulation (고체표면에 응축된 물 분자의 윤활특성에 대한 분자시뮬레이션 연구)

  • Kim, Hyun-Joon
    • Tribology and Lubricants
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    • v.37 no.5
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    • pp.195-202
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    • 2021
  • This paper presents a numerical analysis of the lubrication characteristics of condensed water molecules on a solid surface by conducting molecular dynamics simulations. We examine two models consisting of a simple hexahedral substrate with and without water molecules to reveal the lubrication mechanism of mono-layered water molecules. We perform a sliding simulation by contacting and translating a single asperity on the substrate under various normal loads. During the simulation, we measure the friction coefficient and atomic stress. When water molecules were interleaved between solid surfaces, atomic stress exerted on individual atom and friction coefficient were smaller than those of model without water molecule. Particularly, at a low load, the efficacy of water molecules in the reduction of atomic stress and friction is remarkable. Conversely, at high loads, water molecules rarely lubricate solid surfaces and fail to effectively distribute the contact stress. We found a critical condition in which the lubrication regime changes and beyond the condition, significant plastic deformation was created. Consequently, we deduce that water molecules can distribute and reduce contact stress within a certain condition. The reduced contact stress prevents plastic deformation of the substrate and thus diminishes the mechanical interlocking between the asperity and the substrate.