• Journal of Bio-Environment Control
• /
• v.13 no.4
• /
• pp.209-216
• /
• 2004

This study was aimed to assess the effects of microclimate factors on lettuce chlorophyll fluorescent responses and to develop an environment control system for plant growth by adopting a simple genetic algorithm. The photosynthetic responses measurements were repeated by changing one factor among six climatic factors at a time. The maximum Fv'/Fm' resulted when the ambient temperature was $21^{\circ}C,\;CO_2$ concentration range of 1,200 to 1,400 ppm, relative humidity of $68\%$, air current speed of $1.4m{\cdot}s^{-1}$, and the temperature of nutrient solution of $20^{\circ}C$. In PPF greater than $140{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, Fv'/Fm' values were decreased. To estimate the effects of combined microclimate factors on plant growth, a photosynthesis efficiency model was developed using principle component analysis for six microclimate factors. Predicted Fv'/Fm' values showed a good agreement to measured ones with an average error of $2.5\%$. In this study, a simple genetic algorithm was applied to the photosynthesis efficiency model for optimal environmental condition for lettuce growth. Air emperature of $22^{\circ}C$, root zone temperature of $19^{\circ}C,\;CO_2$ concentration of 1,400 ppm, air current speed of $1.0m{\cdot}s^{-1}$, PPF of $430{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, and relative humidity of $65\%$ were obtained. It is feasible to control plant environment optimally in response to microclimate changes by using photosynthesis efficiency model combined with genetic algorithm.

• Journal of Bio-Environment Control
• /
• v.15 no.1
• /
• pp.47-52
• /
• 2006

This studies were carried out in summer season to increase high temperature tolerance using hydrogen peroxide treatments on cucumber in greenhouse. The water stress of cucumber in greenhouse by the hydrogen peroxide treatments showed as control>250 mM>500 mM treatments in order. The photosynthesis rate of cucumber at $30^{\circ}C$ did not show difference with each hydrogen peroxide treatment in temperature controlled greenhouse. However, the photosynthesis rate of cucumber in the control and hydrogen peroxide treatments at $40^{\circ}C$ was significantly different. The photosynthesis rate of cucumber in combined treatment with 1,000 $mg{\cdot}L^{-1}\;CO_2$ supply and hydrogen peroxide was also higher than control, however, there was no different of photosynthesis in 250 mM and 500 mM treatment. The value of $F_v/F_m$ and $F_m/F_o$ of chlorophyll fluorescent in 500 mM hydrogen peroxide treatment at $40^{\circ}C$ was highest. Also the activity of POD, the antioxidant enzyme, was higher with high hydrogen peroxide concentration than the other treatments. The high temperature limits for growth were $43^{\circ}C$ in the control, $44^{\circ}C$ in the 250 mM and $46^{\circ}C$ in the 500 mM according to analyze chlorophyll fluorescent $F_o$. The high temperature tolerance in cucumber increased approximately $3^{\circ}C$ by the hydrogen peroxide treatments under this experiment conditions.

• Korean Journal of Environment and Ecology
• /
• v.30 no.5
• /
• pp.821-828
• /
• 2016

We examed physiological and flowering response of S. capitata, the endangered plant in Korea, under LED light conditions in plant factory to cultivate artificially for conservation. We cultivated S. capitata and measured its physiological responses and the number of flowers under red, blue, white, red+far-red mixed, red+blue mixed, and red+blue+white mixed light. The results showed that its photosynthetic rate and chlorophyll content were recorded relatively high in red+blue+white and red+blue mixed light respectively. Transpiration rate and stomatal conductance appeared relatively high in the white single light while water use efficiency was no difference. Photochemical efficiency of photochemical photosystem II by minimum and maximum chlorophyll fluorescence was the highest in the red+blue+white mixed light condition than other ones. The number of flowers of S. capitata was at its peak under the red light or red+far-red mixed light. Therefore, we conclude that the most efficient way to grow for flowering of S. capitata is to provide red light or red+far-red mixed light in the plant factory.

• Korean Journal of Environmental Biology
• /
• v.23 no.1
• /
• pp.47-51
• /
• 2005

Three-weeks old Commelina communis was transferred to Hoagland solution (Control, 100 μM Cd/sup 2+/, 100 μM Cd/sup 2+/ + 100 μM ABA, 100 μM Cd/sup 2+/+50 mM KCl) and grown for a week in the solution and then a number of physiological activities were investigated. In cases of Cd/sup 2+/ and Cd/sup 2+/ + ABA treatments, the growth of the plants was inhibited to 71 % and 81 %, respectively, when compared with the control, but there were no significant difference of plant growth between Cd/sup 2+/ and Cd/sup 2+/ + KCl- treated plants. In the treatments of Cd/sup 2+/, Cd/sup 2+/ + ABA and Cd/sup 2+/ + KCl total chlorophyll contents were reduced to 32%, 41% and 29%, respectively. In chlorophyll fluorescence experiments, Fv/Fm ratios were also reduced to 14∼20% and about 23%, respectively, according to the light intensity by Cd/sup 2+/ and Cd/sup 2+/+ABA-treated plants. Water stresses were increased by the treatment of Cd/sup 2+/, Cd/sup 2+/ + ABA and Cd/sup 2+/ + KCI. In Cd/sup 2+/ accumulation experiments Cd/sup 2+/ transport into the plant by ABA was not affected, but the accumulation of Cd/sup 2+/ into the roots was elevated to 13% when compared with the control. Cd/sup 2+/ transport into the root was markedly inhibited to 60% by KCl. Therefore, it could be concluded that ABA did not reduce the toxicities of Cd/sup 2+/, but enhanced Cd/sup 2+/ - induced toxicities and KCl showed no effect on Cd/sup 2+/ - induced toxicities.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.48 no.6
• /
• pp.506-515
• /
• 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 Environmental Biology
• /
• v.36 no.2
• /
• pp.117-123
• /
• 2018

In this study, the efficiency of photosynthetic electron transfer according to LED color temperature was verified in order to find a way to efficiently grow trees under night illumination. The experiment was carried out with White treatment, Warmwhite treatment, and non-treatment with donarium cherry. The study uses to a method for analyzing and evaluating the color temperature of an LED light source by photochemical analysis. We found that all treatments 115 DAT of maximum fluorescence amount(P) had the lowest. In the treatment using white light and the Warm-white light, the T amount of florescence of the late stage during the transition of the J-I level was increased, and the photosystem I electron transfer efficiency was decreased. Therefore, the electron transport efficiency of $RE1_O/CS$ and RE1o/RC were reduced. Especially, compared to Warmwhite, the light intensity increased greatly in the white-light treatment, The $PI_{TOTALABS}$ of 7 DAT was the highest value, but it was decreased to the lowest value on 115 DAT. This study has shown that the white treatment was low in electron transfer efficiency and soundness. Warmwhite-light treatments showed lower stress.

• Korean Journal of Ecology and Environment
• /
• v.35 no.4 s.100
• /
• pp.257-265
• /
• 2002

The current study was performed to elucidate the relationship between the anatoxin -a produced by cyanobacteria and aquatic environmental factors, Algal and water samples were collected from the Daechung Reservoir from June to November 2001. The physical factors of the water quality were measured in sifu, while the biological and chemical factors were examined in the laboratory. The concentrations of anatoxin-a in the algal and water samples were analyzed by HPLC using a fluorescence detector, and ranged from $0.61-8.68\;{\mu}g/g$ dw in the algal samples and $0.01-0.08\;{\mu}g/L$ in the water samples. The suggested maximum concentration of anatoxin-a for safe drinking water is $1\;{\mu}g/L$. The concentrations of anatoxin-a in the algal and water samples were highest in July. The relationships between tile aquatic environmental factors and the anatoxin-a concentration were also analyzed to identify the crucial elements for toxin production. The anatoxin-a concentrations in the algal samples exhibited a high correlation with nitrate, the TN/TP ratio, TDN (P<0.05), and TPN/TPP ratio (P<0.01), whereas the anatoxin-a concentrations in the water samples were highly related to the water temperature, conductivity (P<0.01) , pH, phycocyanin, and phycocyanin/chlorophyll a ratio (P<0.05).

• Journal of Photoscience
• /
• v.9 no.2
• /
• pp.158-161
• /
• 2002

UV-B radiation gives harmful effects on plants, such as production of several types of DNA lesions, and growth inhibition. On the other hand, plants have some protective mechanisms, including filtering effect due to accumulation of phenolic compounds in epidermal cells and reactivation of DNA lesions, which are enhanced by UV-B irradiation. We have investigated the mechanism of UV-B effects on plants using cucumber seedlings as plant materials. Cucumber plants were cultivated in an artificially lit growth chamber. Supplemental UV-B irradiation, of which intensity was almost equal to the level of natural sunlight, retarded the growth of first leaves. The growth retardation must result trom the inhibition of cell division and/or cell growth. Microscopical observation of leaf epidermis suggested that the growth retardation might be mainly caused by cell growth inhibition. The retardation was, however, restored within 2 or 3 days after the termination of UV-B irradiation. It is known that UV-B irradiation lowers the activity of photo system II (PS II). In the present experimental conditions, however, UV-B irradiation has little effect on PS II activity as estimated by chlorophyll fluorescence. The stomatal conductance, a major factor determining photosynthetic rate, of first leaves increased during the growth. The increase of stomatal conductance was suppressed by UV-B irradiation and restored by termination of the irradiation. It has not been clear, however, what mechanisms are involved in the suppression of increase of stomatal conductance.

• ALGAE
• /
• v.29 no.4
• /
• pp.321-331
• /
• 2014

Vertebrata lanosa is an abundant and obligate red algal epiphyte of Ascophyllum nodosum that forms part of a complex and highly integrated symbiotic system that includes the ascomycete, Mycophycias ascophylli. As part of ongoing studies to resolve interactions among species in the symbiosis, we used pulse amplitude modulation fluorimetry of chlorophyll a fluorescence, from photosystem II (PSII), to measure the maximum quantum yield ($F_v/F_m$) of PSII [$QY(II)_{max}$] and relative photosynthetic electron transport rates (rETR), as a function of light intensity, in order to evaluate the photosynthetic capacity of the two algal symbionts in the field and in the laboratory under different treatments. Our primary question was 'Is the ecological integration of these species reflected in a corresponding physiological integration involving photosynthetic process?' In the laboratory we measured changes in $QY(II)_{max}$ in thalli of V. lanosa and A. nodosum over one week periods when maintained together in either attached or detached treatments or when maintained separated from each other. While the $QY(II)_{max}$ of PSII of A. nodosum remained high and showed no significant variation among treatments, V. lanosa showed decreasing performance in the following conditions: V. lanosa attached to A. nodosum, V. lanosa in the same culture, but not attached to A. nodosum, and V. lanosa alone. These results are consistent with observations in which rETR was reduced in V. lanosa maintained alone versus attached to A. nodosum. Values for $QY(II)_{max}$ in V. lanosa measured in the field in fully submerged thalli were similar to those measured in the laboratory when V. lanosa was attached to it obligate host A. nodosum. Our results provide evidence of a physiological association of the epiphyte and its host that reflects the known ecology.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.47 no.5
• /
• pp.341-351
• /
• 2002

In order to examine the mechanistic basis for differential sensitivities to chilling and subsequent recovery between two rice (Oryza sativa L.) cutivars, a chilling-tolerant japonica type (Ilpumbyeo) and a chilling-susceptible indica type (Taebaekbyeo), changes of physiological responses and antioxidant enzymes were investigated. Both cultivars at 3 leaf stage were exposed at a low temperature of $5^{\circ}C$ for 3 days and subsequently recovered in a growth chamber at a $25^{\circ}C$ for 5 days with 250 mmol $m^{-2}$ $s^{-1}$. Physiological parameters such as leaf fresh weight, relative water content, cellular leakage, lipid peroxidation, and chlorophyll a fluorescence showed that the chilling tolerant cultivar had a high tolerance during chilling. However, the chilling-susceptible cultivar revealed severe chilling damages. The chilling-tolerant cultivar was also faster in recovery than the chilling-susceptible cultivar in all parameters examined. We analyzed the activity and isozyme profiles of four antioxidant enzymes which are: superoxide dismutase (SOD), caltalase (CAT), ascorbate peroxidase (APX), and glutation reductase (GR). We observed that chilling-tolerance was due to a result of the induced or higher antioxidant enzyme system, CAT and APX in leaves and SOD, CAT, APX, and GR in roots. Especially, we observed the most significant differences between the chilling-tolerant cultivar and -susceptible cultivar in CAT and APX activity. Also in isozyme profiles, CAT and APX band intensity in the chilling-tolerant cultivar was distinctively higher than in the chilling-susceptible cultivars during chilling and recovery. Thus, the cold stability of CAT and APX are expected to contribute to a tolerance mechanism of chilling in rice plants. In addition, the antioxidative enzymes activity in roots may be more important than in that of leaves to protect chilling damage on rice plants.