• Journal of The Korean Society of Grassland and Forage Science
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• v.31 no.3
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• pp.269-276
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• 2011

To investigate the physiological effects of mycorrhizal colonization on drought stress tolerance in white clover, the responses of leaf water potential (${\Psi}_{PL}$), relative water content (RWC), leaf dry mass, photosynthesis rate, transpiration, stomatal conductance, proline and ammonia were assessed periodically during 7 days in non-AM and AM plants under wellwatered or drought-stressed conditions. Under well-watered conditions, the examined parameters were not significantly changed or very little affected by AM symbiosis. Drought decreased water potential, relative water content, photosynthesis rate, transpiration and stomatal con ductance by 68.6%, 22.7%, 97.7%, 83.9% and 84.9%, respectively, in non-AM plants, meanwhile 46.8%, 13.4%, 50.3%, 44.8% and 54.7%, respectively, in AM plants. In addition, drought increased ammonia and proline by 31.8% and 162%, respectively, in non-AM plants, while 20.9% and 76.9%, respectively, in AM plants. These results clearly showed that mycorrhizal colonization significantly relieved the responses of physiological parameters to drought stress in white clover.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.311-318
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• 2022

Salicylic acid (SA), a phenolic compound, plays a pivotal role in regulating a wide range of physiological and metabolic processes in plants such as antioxidant cellular defense, photosynthesis, and biotic and abiotic stress responses during the growth and development. We examined the effect of exogenous SA application (100 mg·L^-1) on the growth, yield, photosynthetic characteristics, lipid peroxidation, and antioxidant enzyme activity of chili pepper plants under high temperature and drought stress conditions. SA treatment induced increases of net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) under the stress condition with the highest level after the third treatment. The contents of malondialdehyde and H₂O₂ were significantly lower in the third treatment of SA compared to the control. The activity of ascorbate peroxidase, catalase, peroxidase and superoxide dismutase, increased in treated plants by up to 247, 318, 55 and 54%, respectively compared to the nontreated control. There was no significant difference in the growth characteristics between SA-treated and nontreated plants, while the SA treatment increased marketable yield (kg/10a) by about 15% compared to the nontreated control. Taken together, these results suggest that foliar application of SA alleviates physiological damages caused by the combination of drought and heat stress, and enhances the photosynthetic capacity and antioxidant enzyme activities, thereby improving tolerance to a combination of water deficit and heat stress in chili pepper plants.

• Journal of Practical Agriculture & Fisheries Research
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• v.16 no.1
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• pp.67-75
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• 2014

Use of mobile shading helps ameliorate heat stress of cucumber in greenhouse during summer. The mobile shading according to solar radiation may be optimal to produce high-quality cucumber in greenhouse during summer. Simultaneous comparison was made among greenhouse sections that were either not shaded or covered with reflective aluminized shadecloth that shaded 40%, or 90% of direct sunlight. Solar radiation amount, soil temperature, difference in leaf temperature and air temperature, and air temperature were lower, and relative humidity was higher as shade level increased. With increased shade level, photosynthesis rate, leaf area, fresh weight, dry weight, and number of marketable fruits increased. The mobile shading of 90% when the outer sunlight was above 650W·m^-2 yielded favorable growth environment in greenhouse of cucumber during summer.

• Journal of Practical Agriculture & Fisheries Research
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• v.18 no.1
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• pp.71-78
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• 2016

The present study was performed to examine the high temperature adaptability with CO₂ treatment for tomato under the condition of greenhouse cultivation during summer season. The plants with the CO₂ concentration of 1000 ppm recorded higher scores in Fm/Fo and Fv/Fm but lower score in Fo than others through the measurement of chlorophyll fluorescence, which implicated that the plants with the CO₂ concentration of 1000 ppm had more adaptability to high temperature than the others. At the condition of the same air temperature as 30℃ and 40℃, the photosynthetic rate was increased with the increase of CO₂ concentration. When in the high air temperature state of 40℃, although the photosynthic rate was low in comparison with 30℃, its value was about 18.5umolm^-2s^-1 in case of 1000ppm. The higher concentration of CO₂ made the more activated anti-oxidation enzyme (superoxide dismutase and peroxidase) for the both cultivars as 'momotaro' and 'minichal'. The cultivar of 'minichal' performed the high temperature limit as 41℃ at the CO₂ condition of 500 ppm and 43℃ at the CO₂ condition of 1000 ppm through the estimation on the variation of chlorophyll fluorescence Fo by CO₂ concentrations.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.118-126
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• 2009

Benthic diatoms are very important primary producers in understanding estuary ecosystems and their productions are largely varied by their photo-physiological characteristics. The short-term effects of increased temperature on the photosynthetic and photo-physiological characteristics of cultured different species of benthic diatoms (Navicula sp., Nitzschia sp., Cylindrotheca closterium, and Pleurosigma elongatum) were investigated by measuring their PSII-fluorescence kinetics using a Diving-PAM. Photosynthesis versus irradiance curves were measured every two hours at six different temperatures (10, 15, 20, 25, 30, and $35^{\circ}C$) for twenty-four hour. The effective quantum yield of PSII ($\Phi_{PSII}$) for most of the species showed a decreasing trend with increased temperature. The relative maximum electron transport rate (rETRmax) was significantly increased up to the optimum temperature level and then sharply decreased. Relative to the values of other parameters, the maximum light use coefficient ($\alpha$) was not substantially changed at lower temperature levels (<$30^{\circ}C$) but significantly decreased only at higher temperatures (30 and $35^{\circ}C$). The light saturation coefficient ($E_K$) mirrored the rETRmax temperature response. In regards to the temperature acclimation abilities of the four species with time, Navicula sp. and C. closterium acclimated to short-term changes in temperature through their photo-physiological adjustments.

• Journal of Environmental Science International
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• v.25 no.8
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• pp.1143-1153
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• 2016

Plant biomass, photosystem II (PSII) photochemical activity, photosynthetic function, and zinc (Zn) accumulation were investigated in a sorghum-sudangrass hybrid (Sorghum bicolor ${\times}$ S. sudanense) exposed to various Zn concentrations to determine the elimination capacity of Zn from soils. Plant growth and biomass of the sorghum-sudangrass hybrid decreased with increasing Zn concentration. Symptoms of Zn toxicity, i.e., withering and discoloration of old leaves, were found at Zn concentrations over 800 ppm. PSII photochemical activity, as indicated by the values of $F_v/F_m$ and $F_v/F_o$, decreased significantly three days after exposure to Zn concentrations of 800 ppm or more. Photosynthetic $CO_2$ fixation rate (A) was high between Zn concentrations of 100-200 ppm ($22.5{\mu}mol$ $CO_2{\cdot}m^{-2}{\cdot}s^{-1}$), but it declined as Zn concentration increased. At Zn concentrations of 800 and 1600 ppm, A was 14.1 and $1.8{\mu}mol$ $CO_2{\cdot}m^{-2}{\cdot}s^{-1}$, respectively. The patterns of stomatal conductance ($g_s$), transpiration rate (E), and water use efficiency (WUE) were all similar to that of photosynthetic $CO_2$ fixation rate, except for dark respiration ($R_d$), which showed an opposite pattern. Zn was accumulated in both above- and below-ground parts of plants, but was more in the below-ground parts. Magnesium (Mg) and iron (Fe) concentrations were significantly low in the leaves of plants, and symptoms of Mg or Fe deficiency, such as a decrease in the SPAD value, were found when plants were treated with Zn concentrations above 800 ppm. These results suggest that the sorghum-sudangrass hybrid is able to accumulate Zn to high level in plant body and eliminate it with its rapid growth and high biomass yield.

• The Korean Journal of Ecology
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• v.3 no.1_2
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• pp.31-39
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• 1980

Light energy utilization was investigated in the fallen stems of Opuntia bigelovii. Threshold time for the decreasing steady state of acid accumulation in the palisade tissue of Opuntia stems was 4 hours under 1,000 $\mu Em^{-2}sec^{-1}$ of PAR at $75^{\circ}C$, while stomatal closing throughout the stem stage was illustrated by 256.0-310.4 sec $\textrm{cm}^{-1}$ of stem diffusive resistance and 0.20g $day^{-1}$ of the water loss rate as cuticular resistance. The acid loss rate in the stems per 4 hours was related to tissue water contents and a few acid loss rate could be recognized at the water content rage of 56.4%~46.8%. Endogenous oscillation of tissue acidity due to the diurnal rhythmic phenomena depended on the tissue water content was found in the Opuntia stems with stomatal closing during the normal day/night cycle. The survival rate of 1 segment to survive 2 years old cactus was 22.7% in desert environments. Such a compensation photosynthesis which utilizes light energy and maintains the reassimilation of endogenous gases was interpreted as conceptual model.

• Journal of Ecology and Environment
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• v.46 no.3
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• pp.161-171
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• 2022

Background: Epilobium hirsutum L. is designated as an endangered plant in South Korea located in Asia, due to the destruction of its habitats through the development of wetlands. Therefore, in this study, in order to find a light condition suitable for the growth and ecophysiological responses of Epilobium hirsutum L., those of this plant under treatment with various light qualities in a smart farm were measured. Results: In order to examine the changes in the physiological and growth responses of Epilobium hirsutum L. according to the light qualities, the treatment with light qualities of the smart farm was carried out using the red light: blue light irradiation time ratios of 1:1, 1:1/2, and 1:1/5 and a red light: blue light: white light irradiation time ratio of 1:1:1. As a result, the ecophysiological responses (difference between leaf temperature and atmospheric temperature, transpiration rate, net photosynthetic rate, intercellular CO₂ partial pressure, photosynthetic quantum efficiency) to light qualities appeared differently according to the treatments with light qualities. The increase in the blue light ratio increased the difference between the leaf temperature and the atmospheric temperature and the photosynthetic quantum efficiency and decreased the transpiration rate and the intercellular CO₂ partial pressure. On the other hand, the white light treatment increased the transpiration rate and intercellular CO₂ partial pressure and decreased the temperature difference between the leaf temperature and the ambient temperature and photosynthetic quantum efficiency. Conclusions: The light condition suitable for the propagation by the stolons, which are the propagules of Epilobium hirsutum L., in the smart farm, is red, blue and white mixed light with high net photosynthetic rates and low difference between leaf temperature and atmospheric temperature.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.357-365
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• 2016

The effects of elevated atmospheric $CO_2$ on photosynthesis and growth of Chinese cabbage (Brassica campestris subsp. napus var. pekinensis) were investigated to predict productivity in highland cropping in an environment where $CO_2$ levels are increasing. Vegetative growth, based on fresh weight of the aerial part, and leaf characteristics (number, area, length, and width) of Chinese cabbage grown for 5 weeks, increased significantly under elevated $CO_2$ ($800{\mu}mol{\cdot}mol^{-1}$) compared to ambient $CO_2$ ($400{\mu}mol{\cdot}mol^{-1}$). The photosynthetic rate (A), stomatal conductance ($g_s$), and water use efficiency (WUE) increased, although the transpiration rate (E) decreased, under elevated atmospheric $CO_2$. The photosynthetic light-response parameters, the maximum photosynthetic rate ($A_{max}$) and apparent quantum yield (${\varphi}$), were higher at elevated $CO_2$ than at ambient $CO_2$, while the light compensation point ($Q_{comp}$) was lower at elevated $CO_2$. In particular, the maximum photosynthetic rate ($A_{max}$) was higher at elevated $CO_2$ by 2.2-fold than at ambient $CO_2$. However, the photosynthetic $CO_2$-response parameters such as light respiration rate ($R_p$), maximum Rubisco carboxylation efficiency ($V_{cmax}$), and $CO_2$ compensation point (CCP) were less responsive to elevated $CO_2$ relative to the light-response parameters. The photochemical efficiency parameters ($F_v/F_m$, $F_v/F_o$) of PSII were not significantly affected by elevated $CO_2$, suggesting that elevated atmospheric $CO_2$ will not reduce the photosynthetic efficiency of Chinese cabbage in highland cropping. The optimal temperature for photosynthesis shifted significantly by about $2^{\circ}C$ under elevated $CO_2$. Above the optimal temperature, the photosynthetic rate (A) decreased and the dark respiration rate ($R_d$) increased as the temperature increased. These findings indicate that future increases in $CO_2$ will favor the growth of Chinese cabbage on highland cropping, and its productivity will increase due to the increase in photosynthetic affinity for light rather than $CO_2$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.6
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• pp.526-530
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• 1994

This study was conducted to investigate photosynthetic response to four sequential air influx rate with rice(Oryza sativa L.)plants moved from a natural condition to constant condition with automatic regulation selected environmental variables on 13th~15th days after anthesis. In time course of photosynthetic response to increasing air influx rate(200-280-360-440 ml / min.), stomatal conductance decreased rapidly at the beginning after treatment and then oscillated with a free-running period of a approximately 1 hour to 1 hour 30 minutes until reached up to steady-state condition. Similar change was also observed $CO_2$ assimilation rate. Stomatal conductance decreased throughout the air influx rate sequence, but the rate of decrease was similar to the decrease in $CO_2$ assimilation rate observed under continuous air influx rate conditions. In starch granules during grain filling period under air influx rate(440 ml / min.) , compound starch granules were loosing and a number of hollows were observed in surface of single starch granules. Evidences from several approaches indicate that synchronization of stomatal conductance and$CO_2$ assimilation rate was closely inter-related tinder increase of air influx rate and increase of air influx rate influenced the$CO_2$ uptake in photosynthetic processes and compound starch granule, as 'end products' of photosynthesis.