• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.632-638
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• 2000

This paper represents the characteristics of evapotranspiration rate (EVTR) and graft-taking of watermelon grafted seedlings in a graft-taking enhancement system using fluorescent lamps as artificial lighting source. Four air temperature levels of 23, 25, 27 and 29C, three humidity levels of 85, 90 and 95%R.H. and two photosynthetic photon flux (PPF) levels of 30 and 50 ${\mu}$mol m$\^$-2/ S$\^$-1/ were provided to investigate the effects of air temperature, relative humidity and light intensity on EVTR and graft-taking of grafted seedlings. EVTR of grafted seedlings increased with increasing air temperature and the passage of time after grafting. Also EVTR increased with decreasing relative humidity. As relative humidity decreased and air temperature increased, vapor pressure deficit increased and thus EVTR increased. It is required to maintain a low level vapor pressure deficit for suppressing EVTR of grafted seedlings during first 1-2 days after grafting. Therefore, less EVTR at initial stage after grafting would be adequate for smooth joining of the scion and rootstock.

• Korean Journal of Medicinal Crop Science
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• v.20 no.3
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• pp.171-176
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• 2012

This study was conducted to investigate the effect of atmosphere-leaf vapor pressure deficit (VPD) in Allium microdictyon Prokh. and Allium ochotense Prokh. The vapor pressure deficit (VPD) was rapidly increased with increasing temperature and decreasing relative humidity. Taken as a whole, the stomatal transpiration reaction was slightly late with increading of VPD. Maximum photosynthetic rate at high-VPD condition was 5.98 ${\mu}mol$ $CO_2{\cdot}m^{-2}{\cdot}s^{-1}$ in Allium microdictyon, which was a little lower than 6.59 ${\mu}mol$ $CO_2{\cdot}m^{-2}{\cdot}s^{-1}$ in Allium ochotense, respectively. After 2 p.m, stomatal transpiration of Allium microdictyon at the high VPD condition were rapidly decreased. Ci/Ca began to decline sharply at 8 a.m and showed the lowest value at 2 p.m, The results showed that Ci/Ca decreased with being used $CO_2$ in the mesophyll intercellular space for photosynthesis. In high VPD condition, The water potential values showed the highest at 5 a.m, and the lowest at 1 p.m in high VPD condition. The water saturation deficits (WSD) in high VPD condition showed about 1.5 times higher than in low VPD condition. The results indicated that physiological activities in Allium microdictyon is more limited from high VPD conditions.

• 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 Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.785-789
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• 2021

Paprika productivity is different even in the same quality greenhouse and in the same region. These differences are known to due to differences in various environmental factors. This study was conducted to investigate the difference in the level of various environmental factors between high-productivity (HPF) and low-productivity (LPF) greenhouses. The largest difference between the two greenhouses in the daily or weekly average values of major environmental factors was the CO₂ concentration, but the LPF was higher than the HPF, so it was not determined as a factor for the difference in productivity. Correlation analysis among 14 environmental factors showed a high correlation among irradiation or related factors in moisture. The regression coefficients of the linear regression model between vapor pressure deficit and relative humidity were -0.0202kpa in HPF and -0.0262kpa in LPF. In particular, in February and March, the vapor pressure deficit in LPF was 1.5kpa or more, and the cumulative vapor pressure deficit compared to the cumulative irradiation at the early period of cultivation increased rapidly. The reason for the low productivity in LPF is thought to be that the plant was affected by moisture stress due to high vapor pressure deficit and transpiration under low irradiation conditions in the early period of cultivation and in winter.

• Journal of Bio-Environment Control
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• v.10 no.4
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• pp.232-236
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• 2001

Four air temperature levels of 23, 25, 27 and 29$^{\circ}C$, three humidity levels of 85, 90 and 95% R.H. at photosynthetic photon flux (PPF) of 50 $\mu$mol.m$^{-2}$ .s$^{-1}$ were provided to investigate the effect of vapor pressure deficit on the evapotranspiration rate (EVTR) and graft-taking of watermelon grafted seed-increase. Thus EVTR of grafted seedlings increased with increasing air temperature at high humidity of 95%R.H. At relatively low humidity of 85% R.H., grafted seedlings showed a high EVTR and some wilting of scions was observed at this condition. This result would be ascribed to the low supply of water to vascular bundles according to the insufficient joining of scions and rootstocks. Differences in EVTR between 90% R.H. and 95% R.H. were not observed. Grafted seedlings showed high graft-taking at high relative humidity. Relative humidity had highly influenced to the graft-taking as compared to the air temperature. Graft-taking increased with decreasing vapor pressure deficit. Graft-taking greater than 90% was found at vapor pressure deficit less than 0.4kPa which could be obtained at humidity higher than 90% R.H. Therefore it is required to control the humidity higher than 90% R.H. for suppressing EVTR of grafted seedlings and preventing some wilting of scoins and thus enhancing the graft-taking of grafted seedlings.

• Journal of Practical Agriculture & Fisheries Research
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• v.18 no.1
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• pp.63-70
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• 2016

This study was conducted to investigate the effect of atmosphere-leaf vapor pressure deficit (VPD) in Heracleum moellendorffii and Aruncus dioicus var. kamtschaticus. The VPD was rapidly increased with increasing temperature and decreasing relative humidity. Taken as a whole, the stomatal transpiration reaction was slightly late with increasing of VPD. Maximum photosynthetic rate at high-VPD condition was 6.49 µmol CO₂·m^-2·s^-1 in Heracleum moellendorffii Hance, which was a little lower than 5.57 µmol CO₂·m^-2·s^-1 in Aruncus dioicus var. kamtschaticus, respectively. After 2 p.m, stomatal transpiration of Heracleum moellendorffii at the high VPD condition was rapidly decreased. The results indicated that physiological activities in Heracleum moellendorffii are more limited from high VPD conditions.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2004.03a
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• pp.233-234
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• 2004

• Water for future
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• v.29 no.2
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• pp.235-247
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• 1996

Meteorological and soil water content data measured from semiarid watersheds of Lucky Hills and Kendall during the summer rainy and winter periods were used to study the interrelationships between the controlling variables of the evapotranspiration, and to evaluate the effects of variables on daily actual evapotranspiration (ET) estimation. Simple and multiple linear regression (MLR) analyses were employed to evaluate the order of importance of the meteorological and soil water factors involved. The information gained was used for MLR model development. Theavailable energy and vapor pressure deficit were found to be the important variables to estimate actual ET (AET) for both periods and at both watersheds. Therefore, the important variables of evapotranspiration process in these semiarid watersheds appear to be simply the components of energy term in available energy and aerodynamic term in vapor pressure deficit of Penman potential evapotranspiration (PET) equation.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.3
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• pp.87-94
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• 2000

To recommend adequate covering materials and shapes of rice nursery bed for mechanical transplanting rice seedling, measuring of microclimate inside the rice nursery protected by polyethylene tunnel type, polyester tunnel type, and polyester flat type was compared to that outside the nursery. The vapor pressure deficit inside the polyester tunnel and polyethylene tunnel was higher than that outside the tunnel during daytime on a sunny day. During daytime on cloudy with rain day, the vapor pressure deficit inside polyester tunnel was higher than that in polyethylene tunnel or outside the nursery tunnel. The heat fluxes in the rice nursery tunnel during daytime flowed more to the soil than to the outside tunnel. Amounts of soil heat fluxes in polyethylene tunnel were higher than in polyester flat and polyester tunnel. The vertical profile of air temperature inside the nursery tunnel came to inversion during daytime and was lapse during nighttime regardless weather condition. The maximum temperature inside the nursery tunnel were 47.2$^{\circ}C$ in polyethylene tunnel and 37.$0^{\circ}C$ in polyester tunnel which was 21.1$^{\circ}C$ and 10.9$^{\circ}C$ higher than outside the tunnels respectively on sunny day. On cloudy with rain day, the temperature inside nursery tunnel was higher 8.4$^{\circ}C$ and 4.$0^{\circ}C$ polyethylene and polyester tunnel respectively then outside. Daily temperature changes became larger in the polyethylene tunnel, polyester tunnel, and outside the nursery tunnel in order. The rice seedling growth in polyester tunnel was better than the other nursery beds.

• Journal of Forest and Environmental Science
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• v.21 no.1
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• pp.92-97
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• 2005

This research was carried out to elucidate the characteristics of stomatal transpiration, water efficiency, vapor pressure deficit of leaves by the light intensity Kalopanax pictus leaves. The results obtained are summarized as follows: 1. In the upper leaves of Kalopanax pictus seedlings, the stomatal transpiration rate increased continuously with increasing light intensity, but in the middle and lower leaves. it was saturated at $100{\mu}mol\;m^{-2}S^{-1}$. At the light saturated point. the stomatal transpiration rate was in the following order: the upper ($1.29mmol\;H_2O\;m^{-2}S^{-1}$) middle ($0.56mmol\;H_2O\;m^{-2}S^{-1}$) lower leaves ($0.31mmol\;H_2O\;m^{-2}S^{-1}$). 2. In the upper leaves, water use efficiency rapidly increased to $600{\mu}mol\;m^{-2}S^{-1}$, and then decreased. In the middle and lower leaves, it increased to $400{\mu}mmol\;m^{-2}S^{-1}$, and then showed a constant values. 3. The vapor pressure deficit (VPD) in according to leaf positions was linearly decreased with increasing photosynthetic photon flux density (PPFD).