• The Korean Journal of Ecology
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• v.15 no.1
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• pp.47-58
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• 1992

This study is to investigate the change of the seasonal patterns of relative water relations parameters by the pressure-volume curves in pinus koraiensis needles. The osmotic potentials at full water saturated(Ψ0, sat) and at incipient plasmolysis(Ψ0, tlp) increased in growing season, while decreased in non-growing season. The maximum bulk modulus of elasticity(Emax), relative water content(RWCTLP), and relativefree water content(FWCtlp) at incipient plasmolysis in non-growing season were higher than these of growing season. The maximum pressure potential(Ψp, max) varied from 1.16 to 2.18MPa, torgor index(TI) varied from 3.1 to 4.7. The osmole number(Ns/dw) and symplastic water (Vo/DW) were variable seasonally. The maximum water content(Vt/DW) and apoplastic water(AW) were relatively high in early growing stage, and then decreased to needle aging. The pressure potential(Ψp) and water potential(Ψ) in winter needles were rapidly decreased with decreasing of relative water content. The matric potential occupied over 10 percent of water potential with less than-2.0 MPa.

• Journal of Korean Society of Forest Science
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• v.63 no.1
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• pp.28-34
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• 1984

This study was to elucidate the relation between the water relations parameters obtained from P-V curves and stomatal closure. The results obtained are as follows: 1) The water potential at incipient plasmolysis obtained from P-V curves was similar to the water potential at critical stomatal closure. 2) The critical stomatal closure of sun leaves appear at -21 bar (-17 bar, shade leaves) in Pinus koraiensis, -20 bar in Pinus rigida, -22 bar in Pinus densiflora, and -24 bar in Larix leptolepis. On a relative water content basis, the critical stomatal closures of sun leaves appear at 85% (82%, shade leaves) in Pinus kordiensis, 77% in Pinus ragida, 85% in Pinus densiflora, and 70% in Larix leptolepis. 3) The incipient stomatal closures of sun leaves appear at -14 bar (-12 bar, shade leaves) in Pinus koraiensis, -10 bar in Pinus rigida, -15 bar in Pinus densiflora, and -6 bar in Larix leptolepis. On a relative water content basis, the incipient stomatal closures of sun leaves appear at 90% in Pinus koraiensis, 93% in Pinus rigida, 90% in Pinus densiflora, and 93% in Larix leptolepis. 4) The leaf conductance was increased by increase in volume-averaged turgor pressure was linearly increased by increase in relative water content.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.712-723
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• 2015

This study was conducted to develop the SWCC estimation equation using scaling technique, and to investigate relative sensitivity of the SWCC according to the soil water tension, for the four kinds of soil texture such as Sand [S], Sandy Loam [SL], Loam [L] and Clay Loam [CL]. The SWCC estimation equation of scale factor [${\Theta}sc$] (Eq. 1) was developed based on the log function (Eq. 2) and exponential function (Eq. 3). ${\Theta}sc=[({\Theta}-{\Theta}r)/({\Theta}s-{\Theta}r)]$ (Eq. 1) ${\Theta}sc=-0.196ln(H)+0.4888$ (Eq. 2) ${\Theta}sc=0.3804(H)^{(-0.448)}$ (Eq. 3) where, ${\Theta}$: water content (g/g %), ${\Theta}s$: water content at 0.1bar, ${\Theta}r$: water content at 15bar, H: soil water tension (matric potential) (bar) Relative sensitivity of soil water content was decreased as increase soil water tension, those according to soil water tension were 0.952~0.620 compared to 0.1bar case. Relative sensitivity of scale factor was also decreased as increase soil water tension, those according to soil water tension were 0.890~0.577 compared to 0.2bar case.

• Korean Journal of Plant Resources
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• v.11 no.3
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• pp.307-314
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• 1998

The response of water stree under high and low temperatures, was shown differently according to the longer the suspension period of water supply. Leaf photosynthetic rate(LPS), leaf water potential(WP), relative leaf water content and relative soil water content were lower. At the higher temperatures, the percentate of reduction in LPS and WP was greater than at low temperatures. It is suggested that evaporation rate should be higher in the high temperature than the lower temperature. Also leaf water potential was lower at high temperature than at low temperature. After the 9 th day of treatment , LSP was remarkably reduced at high temperature, but the reduction of LPS was not significant at low temperature. Solidago virga-aurea var. asiatic that maintained LPS of 3rd day after treatment was more strong than other varieties at low temperatures. The silting and curling of leaves were observed symptoms of stress on the 9th day at the both temperatures. The leaves of aster scaber and Ligularia fischeri turned red on the 9th day after treatment at low temperature.

• Current Research on Agriculture and Life Sciences
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• v.21
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• pp.1-9
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• 2003

Plants are often subjected to periods of soil and atmospheric water deficit during their life cycle. To find critical levels for identification of tolerant rice variety to salt- and drought-stresses, we investigated the water deficiency in the leaf of a Dongjinbyeo (DJ) cultivar, identified as intolerant variety, subjected to NaCl- and Polyethylene glycol 6000 (PEG)- treatments. The relative water content and water potential in leaf of DJ plant sharply declined along the high concentration and time after treatment in NaCl- and PEG-treated rice plants. To elucidate the method of simple screening of tolerant variety to salt- and drought-stresses, we examined the relationship between relative water content and water potential of leaves in NaCl- and PEG-treated rice plants. The relationship between relative water content and water potential in leaf of DJ plant showed the highest correlation in 80 mM NaCl-treatment, and showed high correlation only 8% PEG treatment. These results indicate that the critical level of salt stress for screening of tolerant rice was 80 mM NaCl at 48 h after NaCl treatment, and the critical concentration of drought stress for screening of tolerant rice was 8% PEG at 96 h after PEG treatment.

• The Korean Journal of Ecology
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• v.16 no.3
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• pp.353-364
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• 1993

To elucidate ecophysiological factors affecting nutural distribution of evergreen broad-leabed trees in Danohad National Marine Park, water potential, relative water content and photosynthetic activities of 4 species, Cammellia japonica, Machilus thunbergii, Castanopsis cuspidata var.sieboldii and Quercus acuta, were potential began to decrease from 07:00h to its minimum value at 13:00h for C. cuspidata var. sieboldii (-14.3bar) and Q. acuta (-19.4bar) at 16:00 h for M. thunbergii(-17.0bar) and at 19:00 h for C. japonica (-14.5bar), and these showed similar trends to relative water content. Photosynthetic activities of 4 species began to increase from 7:00 h and reached maximum values before their minimum values of water potential occureed. Optimum temperature renges of photosynthetic activities was $18~20^{\circ}C$ for C. japonica - M. thunbergii and $14~16^{\circ}C$ for C. cuspidata var. sieboldii Quercus acuta.Q.acuta had the highest light saturation point of $0.4mM/m^2/s$ and C. japonica the lowest of $0.15mM/m^2/s$. Water potential of 4 species subjected to water stress, began to decrease after 1st day of drought and after 21th day of drought, those of C. japonica, M. thunbergii, C. cuspidata var. sieboldii and Q. acuta decreased to species began to decrease after 7th day of drought and after 21th day, those of M. thunbergii, C. cuspidata var. sieboldii and Q. acuta were dropped to about 50% and C. japonica 83.5%. Photosynthetic activity of 4 specie began to decline in the order of C. cuspidata var. sieboldii, Q.acuta, C. japonica and M. thunbergii after 10th day of drought. These results suggest that the segregated disributions of C. japonica - M. thunbergii on vally positions and C. cuspidata var. sieboldii - Q. acuta on slopes were associated with different responses of water status and photosyntheties to their environment.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.1
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• pp.55-58
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• 1999

Plant water status during growth is directly and indirectly associated with seed yield. The objective of the present study was to determine the genotypic differences in leaf water characteristics at an early growth stage of soybean [Glycine max (L.) Merrill] plants through the pressure-bomb technique. Measurements of water potential as well as relative water content (RWC) were made at the third leaf from the fully-expanded top leaf of eight different soybean genotypes grown for 31 to 35 days after field emergence. On the basis of the modified exponential model, pressure-volume (PV) curves were fitted well ($R^2$=0.92＊＊ to 0.99＊＊ for the curvi-linear region and R=0.67＊＊ to 0.96＊＊ for the linear region), indicating that a segmented model using PROC NLIN of SAS could be used effectively to estimate the leaf water characteristics. The regression analysis for the pressure-volume (PV) curve revealed genotypic variation in the solute potential at saturation (Ψ$_{s,sat}$ :-10.7 to -14.8 bar), solute potential at incipient plasmolysis (Ψ$_{s,ip}$ : -14.3 to -18.3 bar), RWC at incipient plasmolysis (RW $C_{ip}$ : 83.3 to 91.7%), high integrated turgor pressure from saturation to plasmolysis ( $_1$$^{b}$ : 0.39 to 0.81), and maximum volumetric modulus of elasticity ($\varepsilon$$_{max}$ : 150 to 445 bar).).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.506-515
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• 2003

Six barley varieties that showed different degree of drought tolerance were grown with and without drought stress treatment (control), and investigated for the temporal changes in growth and several physiological traits after drought treatment. Soil water potential was -0.05 ㎫ at the initial stage of drought treatment and dropped to -0.29 ㎫ at 19 days after withholding irrigation. Soil water potential (SWP) maintained at -0.05 ㎫ in the control. The dry weight (DW) under the drought treatment were reduced compared to the control as follows: Dicktoo-S (short awn), 69% ; Dicktoo-L (long awn), 70%; Dicktoo-T (tetra), 86%; Dongbori-1, 69%; Suwonssalbori-365, 55% and Tapgolbori, ,37%. Dicktoo lines and Dongbori-1 were more tolerant than Suwonssalbori-365 and Tapgolbori. Leaf relative water contents (RWC) and leaf water potential (LWP) decreased obviously under the drought condition, the decrease being greater especially in the less drought-tolerant barley genotypes. Dongbori-1 and Dicktoo-L in drought treatment showed net photosynthesis of 38% and 17% compared to the control, respectively, and the other four genotypes much lower photosynthesis of 1.1% to 7.0%. Stomatal conductance, mesophyll conductance, and the photochemical efficiency (Fv/Fm) of PS II were reduced by drought treatment, the reduction being greater in drought-sensitive genotypes. The drought-tolerant genotypes had greater osmotic adjustment (OA) capacity under water stress. Thus, the decrease of RWC and LWP was lower and the turgor pressure conservation capacity was higher under water stress in drought-tolerant genotypes. Drought-tolerant genotypes showed less decrease of photosynthesis because stomatal conductance, mesophyll conductance and the ratio (Fv/Fm) of the variable to maximal fluorescence of drought-resistant genotype was decreased less in the drought stress condition. In conclusion, the drought-tolerant genotypes had better water conservation capacity through efficient OA, and this led to the lower decrease of photosynthesis and growth in water stress condition.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.5
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• pp.632-639
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• 1997

The experiment which imposed the water stress to tobacco(Nicotiana tabacum L.) plant was carried at the late of maximum growth period. In order to know the influence of drought stress on the growth and developmemt of tobacco leaves of different position and to elucidate the physiological response of plant to various soil water content, stomatal conductance, and leaf water potential were measured. The drought stress at the maximum growth period negatively affected to the overall growth characteristics of shoot. The response of the growth was small at the middle and the lower leaves, and great at the upper leaves. The relative water content of upper, middle, and lower leaves at the fifth day after treatment were 74, 64, and 59%, respectively, as soil water content was reduced by 4.3%. This suggested that the wilting point of tobacco leaf was about 75%. The leaf water potential was -0.58 MPa in control and dropped to -1.20 MPa at the fifth day after treatment. This indicated that wilting of leaf may occur at the condition in which the difference of water potential between treatment and control, well watered, was greater than about 20%. Stomatal conductance at the fifth day after treatment dropped from 12 mol /$\textrm{m}^2 sec^{-1}$ to 0.8 mol /$\textrm{m}^2 sec^{-1}$ in the middle and the upper leaves. Stomatal conductance of lower leaves already matured were not affected highly by drought stress at the maximum growth period, but maturing leaves, middle and upper leaves, were highly affected by limitation of soil water.

• The Korean Journal of Ecology
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• v.9 no.4
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• pp.201-208
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• 1986

The water status of the leaves of several evergreen plants was investigated in order to discuss the geopgraphical distribution of them. Relastionship between relative water content and water potential of the leaves showed linear decrease for evergreen conifers but exponential decrease for Korean box tree (Buxus microphylla var. koreana). On the basis of the leaf water potential, the water status of the conifers during wintering was distinctly divided into three periods; hardening, cold resistance and dehardening, but lacking in those periods for the Korean box tree, where the status continously decreased. In the cold resistance the leaf water potentials were -23 bar for both spruce (Picea jezoensis) and yew (Taxus cuspidata). From these results and threshold temperature at beginning of hardening, distribution of the conifers was explained that in order of the red pine, the Korean white pine, the yew and the spruce the distribution could be extended at higher altitudes and in more northward areas, whereas the distribution of the Korean box tree was restricted to the lowland of temperate zone.