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

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

• KIPS Transactions on Software and Data Engineering
• /
• v.12 no.3
• /
• pp.125-132
• /
• 2023

In this study, we compared the performance of machine learning models for predicting Vapor Pressure Deficits (VPD) in greenhouses that affect pore function and photosynthesis as well as plant growth due to nutrient absorption of plants. For VPD prediction, the correlation between the environmental elements in and outside the greenhouse and the temporal elements of the time series data was confirmed, and how the highly correlated elements affect VPD was confirmed. Before analyzing the performance of the prediction model, the amount and interval of analysis time series data (1 day, 3 days, 7 days) and interval (20 minutes, 1 hour) were checked to adjust the amount and interval of data. Finally, four machine learning prediction models (XGB Regressor, LGBM Regressor, Random Forest Regressor, etc.) were applied to compare the prediction performance by model. As a result of the prediction of the model, when data of 1 day at 20 minute intervals were used, the highest prediction performance was 0.008 for MAE and 0.011 for RMSE in LGBM. In addition, it was confirmed that the factor that most influences VPD prediction after 20 minutes was VPD (VPD_y__71) from the past 20 minutes rather than environmental factors. Using the results of this study, it is possible to increase crop productivity through VPD prediction, condensation of greenhouses, and prevention of disease occurrence. In the future, it can be used not only in predicting environmental data of greenhouses, but also in various fields such as production prediction and smart farm control models.

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

• The Journal of the Convergence on Culture Technology
• /
• v.7 no.4
• /
• pp.785-789
• /
• 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
• /
• v.16 no.3
• /
• pp.174-179
• /
• 2007

Although the relationship between fermentation and factors such as soil water, redox potential, rootstocks and climatic conditions has been reported, its mechanism of fermentation is still not clear. Transpirations of leaf and fruit at different climatic conditions, influence of soil water potential and atmospheric vapor pressure deficit (VPD) on fermentation were evaluated. Transpiration rate decreased with decreasing soil temperature and soil water potential. Low VPD conditions which occurred during low air temperature and high humidity also decreased transipration rate. These data exhibit that fruit water balance affected by various factors relate to transpiration. Our results also indicate that high hydraulic conductance of root, high soil water potential and low VPD condition exert a significant effect on fermention of oriental melon and so called "water filled fruit".

• Journal of Korea Water Resources Association
• /
• v.54 no.10
• /
• pp.779-793
• /
• 2021

Water stress and environmental drivers are important factors to explain the variance of gross primary production (GPP). Environmental drivers are used to generate GPP in Moderate Resolution Imaging Spectroradiometer (MODIS) algorithm and process-based model. However, MODIS algorithm only consider the vapor pressure deficit (VPD) data while the process-based biogeochemical model also uses limited data to express water stress. We compared the relationship between environmental drivers and GPP from eddy covariance method, MODIS algorithm, and Community Land Model 4 (CLM 4) simulation in normal years and drought years. To consider water stress specifically, we used VPD and evaporative fraction (EF). We evaluated the effects from environmental drivers and EF towards GPP products using the structural equation modeling (SEM) in South Korea. We found that GPP products from MODIS algorithm and model simulation results were not restricted from VPD data if VPD was underestimated. We also found that in the cropland area, irrigation effects can relieve VPD effects to GPP. However, GPP products derived from MODIS and CLM 4 had limitation to explain the irrigation effects to GPP. Overall, these results will enhance the understanding of GPP products derived from MODIS and CLM 4.

• Horticultural Science & Technology
• /
• v.32 no.3
• /
• pp.340-345
• /
• 2014

Since the moisture content (MC) of growing medium closely related with the crop transpiration, the MC should be included to the environmental factors to be considered for irrigation control in soilless culture. The objective of this study was to analyze the transpiration of paprika plants using daily mean solar radiation (RAD) and vapor pressure deficit (VPD) as well as the growth of the plants at different MCs of rockwool growing media. The starting points of irrigation were controlled by a moisture sensor with minimum set points of 40%, 50%, and 60% of MCs. The canopy transpirations were measured for 80 to 120 days after transplanting and analyzed. The transpirations were well regressed with a combination of both RAD and VPD rather than daily mean RAD only under the controlled MCs. The transpiration at 60% MC was higher than those at 50% and 40% MCs. Leaf area, leaf fresh and dry weights at 60% MC were higher than those at 50% and 40% MCs while the number of leaves had no significant difference among the MCs. There were no significant differences in number of fruits and fruit size among all the MCs, while fruit weight was significantly lower at 40% MC than other treatments. Fresh and dry fruit yields were the highest at 60% MC. Therefore it was concluded that the transpiration was affected by the MC of rockwool growing medium and the minimum set point of 50-60% MC of rockwool growing medium gave better effects on the growth of the paprika plants.

• Korean Journal of Soil Science and Fertilizer
• /
• v.48 no.5
• /
• pp.499-504
• /
• 2015

Decision making by farmers regarding irrigation is critical for crop production. Therefore, the precision irrigation technique is very important to improve crop quality and yield. Recently, much attention has been given to remote sensing of crop canopy temperature as a crop water-stress indicator, because it is a scientifically based and easily applicable method even at field scales. This study monitored a series of time-variant canopy temperature of cucumber under three different irrigation treatments: under-irrigation (control), optimal-irrigation, and over-irrigation. The difference between canopy temperature ($T_c$) and air temperature ($T_a$), $T_c-T_a$, was calculated as an indicator of cucumber water stress. Vapor pressure deficit (VPD) was evaluated to define water stress on the basis of the temperature difference between leaf and air. The values of $T_c-T_a$ was negatively related to VPD; further, cucumber growth in the under- and over-irrigated fields showed water stress, in contrast to that grown in the optimally irrigated field. Thus, thermal infrared measurements could be useful for evaluating crop water status and play an important role in irrigation scheduling of agricultural crops.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.6
• /
• pp.1097-1101
• /
• 2023

As paprika plants grew in a glass greenhouse from November 2022 to March 2023, the amount of light at each plant height, leaf temperature, transpiration rate, and water vapor pressure were measured. Accumulated leaf temperature was higher at the top of the plant than at the bottom. Over time, the leaf temperature measured around 11-13 AM changed from 26.55→23.21→22.80→26.67℃ in the lower part (pL), and from 26.52→24.48→24.55→27.78℃ in the upper part (pAs). And VPD changed from 1.45→0.94→0.74→1.46kPa in pL and from 1.11→0.86→0.71→1.28kPa in pAs. Accordingly, the transpiration rate changed from 4.25→0.17→4.08→0.52mmol·m^-2·s^-1 in pL, 7.61→2.45→1.94→4.39→0.52mmol·m^-2·s^-1 in pAs, and from pAs to pL. It was significantly higher than The difference between the lower and upper parts (pL-pAs) was higher in pAs than pL in leaf temperature, light intensity, and transpiration rate, but the water vapor pressure difference was higher in pL. In this way, paprika shows differences in the environment and photosynthetic factors between the upper and lower parts during the cultivation period, so it is judged that this needs to be taken into consideration in future research.