• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.2
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• pp.81-88
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• 2003

Soybeans [Glycine max (L.) Merr.] are frequently exposed to unfavorable environments during growing seasons and water is the most important factor limiting for the production system. The purpose of this study was to determine the leaf water potential changes by irrigation, and to evaluate the relationships of leaf water potential, growth and yield in soybeans. Three soybean cultivars, Hwangkeumkong, Shinpaldalkong 2, and Pungsannamulkong, were planted in growth chamber and field with irrigated treatments. Leaf water potential of three soybean cultivars was positively correlated with leaf water content during vegetative and reproductive growth stages in growth chamber and field experiments. Leaf water potentials measured for three soybean cultivars under growth chamber were higher than those of under field conditions. Higher leaf water potential with irrigated plots under field was observed compared to conventional plots during reproductive growth stages. Leaf water potentials of three soybean cultivars were continually decreased during reproductive growth stages under field and there was no significant difference among them. Number of leaves, leaf water content, pod dry weight, number of seeds and seed dry weight with irrigated plots were higher than those of conventional plots. The results of this study suggested that leaf water potential could be used as an important growth indicator during the growing season of soybean plants.

• The Korean Journal of Ecology
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• v.21 no.1
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• pp.89-96
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• 1998

The diurnal changes of the stomatal conductance, transpiration and leaf water potential were measured in order to assess the water relations characteristics of Pueraria thunbergiana in August of 1995 and 1996. The results showed two different responses depending on the duration of rainless days. The microclimatic conditions were highly stressful on 2 August. Daily maximum temperature reached to $39.0{\circ}C$ and vapor pressure deficit was 3.55 KPa. During this time the leaf water potential decreased to -1.02 MPa and a marked reduction of stomatal conductance was shown. However, on 15 August the stomatal conductance increased with increment of photon flux density, and transpiration was highly maintained during the day time. Minimum leaf water potential was only -0.47 MPa in spite of high transpiration rate. Furthermore, on 15 August reduced leaf water potential during the day time was recovered rapidly with decrease of photon flux density, whereas recovery of leaf water potential on 2 August was delayed. However, reduced leaf water potential on 2 August was recovered untile the next dawn. Osmotic potential at turgor loss point of Pueraria thunbergiana on 2, 3 and 15 August was -1.79, -1.70 and -1.60 MPa, respectively. The vapor pressure deficit is more contributive to the regulation of stomatal conductance than leaf water potential.

• The Korean Journal of Ecology
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• v.24 no.4
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• pp.223-226
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• 2001

The leaf water relations and photosynthetic rate during acute soil drying were compared in potgrown grapevine cultivars, Vitis vinifera cv. Chardonnay and V. vinifera cv. Riesling. Leaf water potential in Riesling decreased significantly from day 2 after water had been withheld, while in Chardonnay leaf water potential for the water-stressed plants was almost identical with that in well watered plants during the first 4 days. Higher stomatal conductance and photosynthetic rate in Chardonnay than Riesling were observed until day 3 after withholding water. Photosynthetic rate in water-stressed Chardonnay was not different from that in control plants until day 3 after withholding water, while that in water-stressed Riesling was reduced markedly from day 2. In Riesling, osmotic potential at turgor loss point was not changed irrespective of watering conditions. However, in Chardonnay osmotic potential at turgor loss point decreased more in the water stressed conditions than in well watered conditions. The osmotic adjustment in Chardonnay under water stress conditions must contribute to the maintenance of higher stomatal conductance and photosynthetic rate than those in Riesling for a significant period of the drying process. Though difference in stomatal conductance between the two cultivars was shown in the process of soil drying, stomatal conductance of both cultivars responded to vapor pressure difference between leaf and ambient air, rather than soil water status and leaf water potential.

• Journal of Environmental Science International
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• v.22 no.2
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• pp.187-193
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• 2013

Dry matter allocation characteristics of Calystegia soldanella, grown in pots, was analysed to assess its plasticity in response to water-stressed conditions. As water was withheld leaf water potential between the two watering treatments was similar during the first 6 days, followed by a rapid decrease in water-stressed plants. The minimum leaf water potential was -1.50 MPa on day 15 and the maximum leaf water potential was about -0.5 MPa on day 0 in water-stressed plants. In well-watered plants leaf water potential was maintained almost consistently throughout the experiment. There was no significant difference in plant dry weight between the two watering treatments for 9 days after the start of experiment and that was remarkably increased thereafter, compared with that remained without any increase in water-stressed plants. In dry mass partitioning, however, the water-stressed plants showed a great plasticity, showing that there were 1.81, 1.35 and 0.81 times increase in root, stem and leaf, respectively. Dry mass partitioning in well-watered plants varied from 2% to 5%. The difference of dry mass partitioning between the two watering treatments was reflected in leaf mass per unit area (LMA) and root/shoot (R/S) ratio. LMA in water-stressed plants was lower than that in well-watered plants, while R/S ratio in water-stressed plants was higher in well-watered plants. This means that the water-stressed plants reduced its leaf area and increased dry mass partitioning into root and stem during the progress of soil drying. These results indicate that Calystegia soldanella inhabiting in sand dune cope with water stress with high plasticity which can adjust its dry mass partitioning according to soil water conditions.

• The Korean Journal of Ecology
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• v.13 no.1
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• pp.59-66
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• 1990

Changes in water potential, lethal temperature and carbohydrate content in the leaves of wintergreen (Pyrola japonica) during overwintering were investigated. Leaf water potential was kept at -2 bars in the tender stage before October, decreased to -46 bars in the dormancy stage and increased to -2 bars again after dehardening Lethal temperatures of the leaf tissue were $-7^{\circ}C$ in the tender stage and $-7^{\circ}C$ in the dormancy stage, but did not recover up to that of the tender stage during dehardeding. Peak of soluble sugar content coincided with the nadir of the leaf water potential. There were close relationships among daily minimum air-temperature, leaf water potential and lethal temperature in changing patterns during overwintering.

• Journal of Korean Society of Forest Science
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• v.54 no.1
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• pp.76-79
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• 1981

This thesis emphasize on diurnal changes of leaf water potential in relation to differences of cutting arrangement. 1. The more is leaves attached to the cutting, the higher is water stress in the cutting compared with less leaves. 2. The less is diameter of cut-part, the more are shown changes in increased and decrease in diurnal leaf water potential. 3. The more is length of stem, the more are shown water stress in diurnal leaf water potential 4. There is no differences between earthen-ball cutting and non-earthen ball cutting in diurnal leaf water potential. 5. Cuttings with two year's slip, compared with one year's leaf water potential increases slowly, dry weigh of root and numbers of rooted cutting are most likely dependent upon other factors rather than the water stress.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.3
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• pp.223-231
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• 1994

To investigate effects of water stress on leaf water potential, nitrate reductase activity and abscisic acid content, Paldalkong, Saealkong and Danyeobkong were subjected to water stress by polyethyene glycol(PEG, MW=6,000) in the water culture and withholding irrigation in soil culture. Leaf water potential and nitrate reductase activity decreased with increaseing of PEG concentration in the water culture. These were higher at 3rd and 5th leaf stage than at 1st leaf stage. Leaf water potential showed no significant differance among the varieties, but nitrate redutase activity was higher in Paldalkong than in Saealkong and Danyeobkong. Leaf water potential and nitrate reductase activity decreased approximately 2.2 times (-1.67 MPa/-0.75MPa) and 47%(3.1${\mu}$ mole nitrite/g.DW/hour/15.9${\mu}$ mole nitrite/g.DW/hour) to control, respectively, after 3 days from water stress treatment in the soil culture. According to increasing PEG concentration, abscisic acid content increased in the water culture and was higher at 5th leaf stage than at 1st and 3rd leaf stage. Paldalkong showed the highest abscisic acid content. Abscisic acid content increased approximately 1.7 times (9.9nmole/g.DW/5.7nmole/g.DW) compared to the control after 3 days from water stress treatment in the soil culture.

• Journal of Environmental Science International
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• v.10 no.1
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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.

• Journal of Environmental Science International
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• v.25 no.1
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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.

• 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).).