• Korean Journal of Soil Science and Fertilizer
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• v.46 no.1
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• pp.32-39
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• 2013

The relationship between relative water contents of lettuce leaves and biochemical activities in lettuce was examined in this study to explore an adaptation response of lettuce to water stress from soils. Soil water contents and relative water contents of leaves were positively related to show $R^2$=0.8728. Hydrogen peroxide contents of leaves rapidly increased with reduction of soil water content, whereas soluble protein contents and dry matters rapidly decreased. And chlorophyll a and b contents of leaves decreased with increase in carotenoid content. Furthermore, the activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) increased dramatically, and mRNA transcript levels of APX, MDHAR and DHAR also increased. Relationship of relative water content of lettuce leaves to hydrogen peroxide, to ascorbate peroxidase activity, to dehydroascorbate reductase activity, and to monodehydroascorbate reductase activity was shown to be positively correlated. It is highly plausible from this study that these enzyme activities could be developed as an indicator of water states in soils.

• Journal of Environmental Science International
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• v.20 no.12
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• pp.1509-1519
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• 2011

The protective effect of nitric oxide (NO) on the antioxidant system under paraquat(PQ) stress was investigated in leaves of 8-week-old lettuce (Lactuca sativa L.) plants. PQ stress caused a decrease of leaf growth including leaf length, width and weight. Application of NO donor, sodium nitroprusside (SNP), significantly alleviated PQ stress induced growth suppression. SNP permitted the survival of more green leaf tissue preventing chlorophyll content reduction and of higher quantum yield for photosystem II than in non-treated controls under PQ exposure, suggesting that NO has protective effect on chloroplast membrane in lettuce leaves. Flavonoids and anthocyanin were significantly accumulated in the leaves upon PQ exposure. However, the rapid increase of these compounds was alleviated in the SNP treated leaves. PQ treatment resulted in lipid peroxidation and induced accumulation of hydrogen peroxide ($H_2O_2$) in the leaves, while SNP prevented PQ induced increase in malondialdehyde (MDA) and $H_2O_2$. These results demonstrate that SNP serves as an antioxidant agent able to scavenge $H_2O_2$ to protect plant cells from oxidative damage. The activities of two antioxidant enzymes that scavenge reactive oxygen species, superoxide dismutase (SOD) and catalase (CAT) in lettuce leaves in the presence of NO donor under PQ stress were higher than those under PQ stress alone. Application of 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), a specific NO scavenger, to the lettuce leaves arrested SNP mediated protective effect on leaf growth, photosynthetic pigment and antioxidant systems. However, PTIO had little effect on lettuce leaves under PQ stress compared with that of PQ stress alone. The obtained data suggest that the damage caused by PQ stress is in part due to increased generation of active oxygen by maintaining increased antioxidant enzyme activities and SNP protects plants from oxidative stress. From these results it is suggested that NO might act as a signal in activating active oxygen scavenging system that protects plants from oxidative damage induced by PQ stress and thus confer PQ tolerance.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.4
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• pp.498-505
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• 2010

To evaluate the effectiveness of AMF on the growth of horticultural crops, we compared mycorrhizal and non-mycorrhizal plants, lettuce (Lactuca sativa L.), that were inoculated with AMF propagules. As compared to the AMF- seedlings, in AMF+ seedlings at 3 weeks after sowing, the number of leaves increased 9%, leaf fresh weight increased 59%, leaf area increased 58%, and leaf length and width increased 21-22%, and chlorophyll content increased 2%. Furthermore, at 9 weeks after sowing, compared to the AMF- plants, in lettuce plants inoculated with AMF at the sowing and transplanting stages, the number of leaves increased 21% and 18%, leaf fresh weight increased 51% and 41%, root fresh weight increased 56% and 47%, and chlorophyll content increased 18% and 19%, respectively. Further this experiment indicated that the growth responses of lettuce plants inoculated with AMF during transplanting were similar to those inoculated with AMF during sowing. The results imply that the AMF infection timepoint is not important. The P content in the leaves of lettuce plants inoculated with AMF during transplanting was significantly higher (217%) than that of leaves from lettuce plants not inoculated with AMF. In contrast, the P content of the leaves of lettuce plants inoculated with AMF during the sowing stage was similar to that of leaves of control lettuce plants. In this experiment, P and chlorophyll content in AMF+ lettuce plants were higher than in AMF- plants, indicating that the photosynthetic rate was improved with AMF inoculation.

• The Journal of Natural Sciences
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• v.9 no.1
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• pp.39-44
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• 1997

This study was aimed to observe the effects of municipal sewage sludge as nutrients on the growth of Lettuce. The effects of heavy metal components of the sludge were also observed. Municipal sewage sludge from Taejon City were treated to the soil of PaiChai University Farm in order to make gradient of nitrogen concentration in soil among 6 experimental groups. Results are as follows ;The longest leaves and roots were produced in control pot, in which urea was supplied as nitrogen source to the soil. Any other sludge-treated groups produced shorter leaves and roots than control group, but the more sewage sludge treated the longer leaves and heavier vegetables were observed. No differences were observed among from 6 experimental groups in the view of N, K, Ca and Mg contents. But P contents in leaves from 6 groups varied. Zn content of Lettuce when was 65.8 mg/kg when it grew with sludge 200%. The groups treated with sludge 200% produced the vegetables of highest Zn contents. Accumulation of Zn, Mn and Cd was more heavier in Lettuce than in Altari radish. Accumulation of Zn, Mn, Cu and Cd in lettuce was not heavier than natural contents of those in market vegetables.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.146-155
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• 2016

The field feasibility tests for a phytoextraction process were performed to identify the effect of citric acid as a chelate on the uranium (U) transfer into the plant for the naturally U contaminated soil in Duckpyeongri, Korea. For the feasibility tests, lettuce and Chinese cabbage were cultivated for 49 days on four testing grounds ($1m{\times}1m{\times}0.5m$ in each) in 2016. The citric acid solution was added to two testing grounds (one for lettuce and the other for Chinese cabbage) increasing the U transfer in two crop plants and their results were compared to those without the citric acid solution. When without the citric acid solution, the U concentration of plant after the cultivation was low (< $45{\mu}g/kg$ for leaves and < $450{\mu}g/kg$ for roots). However, with the addition of 50 mM citric acid solution, the U concentration of lettuce leaves and roots increased by 24 times and 1.8 times, and the U concentration of Chinese cabbage leaves and roots increased by 86.7 times and 5.4 times. The absolute accumulated U amount (${\mu}g$) in lettuce and Chinese cabbage also increased by 8.7 times and 50 times, compared to those without citric acid solution. Less than 8% of the U amount of exchangeable/carbonate phases was removed by using the lettuce and Chinese cabbage when the citric acid solution was not applied. However 52% and 66% of the U amount in exchangeable/carbonate phases were removed by the lettuce and the Chinese cabbage when the citric acid solution was added. The effect of the citric acid on the U transfer capability into the plants was quantitatively investigated by the field feasibility test, suggesting that U existing as exchangeable/carbonate phase in soil can be successfully removed by the phytoextraction process using Chinese cabbage with citric acid.

• Journal of Plant Biotechnology
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• v.7 no.3
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• pp.195-202
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• 2005

The effects of constituent amino acids of glutathione (GSH), glutamate (Glu), cysteine (Cys) and glycine (Gly), on GSH synthesis in lettuce seedlings were examined in this study. The GSH concentration of the seedlings was increased to 5.1-fold and 1.6-fold the concentration of the control in the first leaves and roots, respectively, by simultaneous application of these constituent amino acids (Glu+Cys+Gly) at 100 mg/l to the culture solution for two days. In the first leaves and roots of these seedlings, the concentration of GSH was 180.4 and 14.6 nmole/gFW, and non-essential amino acids including Glu, Cys and Gly occupied 93.2% and 84.0% of the total free amino acids, respectively. Application of Cys greatly increased the concentration of GSH in the roots, and application of 50 mg/l Cys increased it to 26.1-fold the concentration in the control. The activity of GSH synthetase was higher in the leaves than in the roots, whereas the activity of ${\gamma}$-glutamylcysteine synthetase was higher in the roots than in the leaves.

• The Korean Journal of Pesticide Science
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• v.18 no.2
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• pp.53-60
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• 2014

This study was conducted to investigate the changes of the residual amount in the leafstalk (end) and the fore-end (upper) portion of lettuce leaves during cultivation period to 14 days, 12 times in total (0, 1, 2, 3, 4, 5, 7, 8, 10, 12, 13 and 14 days) after spraying with boscalid and lufenuron. In the case of boscalid, the initial concentrations at 3 hours (0 day) of the leafstalk and the fore-end portion of lettuce leaves were 18.26 mg/kg and 84.97 mg/kg, respectively and the residual amounts were rapidly decreased to 0.31 mg/kg and 0.37 mg/kg at 14 days after chemical application. In the case of lufenuron, the initial concentrations at 3 hours (0 day) of the leafstalk and the fore-end portion of lettuce leaves were 0.91 mg/kg and 5.21 mg/kg, respectively and the residual amounts were rapidly decreased to 0.06 mg/kg and 0.09 mg/kg at 13 days after chemical application. The variations of the residual concentrations analyzing 12 times after spraying showed that the residual amounts of the leafstalk portion of lettuce leaves were less than its fore-end portion in boscalid and lufenuron. In additon, 9 kinds of pesticide including boscalid in 16 lettuce leaf (found to contain pesticide in 2013) showed that the residual amounts of the leafstalk portion of lettuce leaves were less than its fore-end portion as well.

• Journal of Environmental Science International
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• v.33 no.5
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• pp.305-322
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• 2024

The aim of this study was to investigate the effects of artificial light sources on the germination and seedling vigor of lettuce, aiming to identify the optimal artificial light source for producing high-quality seedlings. Lettuce cultivar of 'Tomalin' and 'Seonpunggold' exhibited the highest seed emergence in the Metal halide(MH) lamp and High-pressure sodium(HPS) lamp treatment group, while the emergence rate parameter, T50, was the fastest in the HPS lamp treatment group. Both cultivars showed good growth characteristics such as number of leaves, root length, and stem diameter under RGB-LED, and their seedling vigor was excellent as well. The plant height was smallest in the Red + Green + Blue LED treatment, but the leaves were round and thick, resulting in higher biomass and dry weight. Single light sources of Red LED and Blue LED led to reduced growth compared with that under the mixed light treatments. Chlorophyll content in lettuce varied with the type of artificial light, with both cultivars exhibiting the highest chlorophyll content in the Red + Green + Blue LED treatment. The most suitable artificial light for lettuce seedling growth was the Red + Green + Blue LED treatment.

• Plant Resources
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• v.8 no.2
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• pp.103-109
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• 2005

Lettuce (Lactuca sativa L.) is known to contain water-soluble substances that improve antioxidant status due to the richness in antioxidants. Greenhouse experiment was carried out under different shading conditions during spring lettuce growing season. Shade significantly reduced shoot weight, number of leaves and chlorophyll content, while it increased shoot length of lettuce plants. The antioxidant potential of the individual fraction was in order of n-butanol > ethyl acetate > water > n-hexane fraction, although was less than that of commonly used antioxidants, BHT and ascorbic acid. Fractions from lettuce plants dose-dependently increased DPPH free radical scavenging activity, in vitro test. By means of HPLC analysis, BuOH fraction of cultivar 'Hwahyang' (57.93 mg $100g^{-1}$) had the highest amount of antioxidant chi orogenic acid. Shading treatment increased average amount of chlorogenic acid of all cultivars in BuoH, EtOAc, hexane and water fractions by 33, 120, 144, and $58\%$, respectively. These results suggest that lettuce plants had potent antioxidant activity, and their activities were differently exhibited depending on cultivar and fraction.

• Plant Resources
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• v.2 no.1
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• pp.26-30
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• 1999

Nitrate in edible vegetables is converted to nitrite by nitrate reductase(NR) and/or bacteria in intestines. Nitrite and amino, in the intestine of some animals and human, bind to form nitrosamine, which is toxic and known as carcinogen. This study was carried out to examine the effect of added chlorides and their concentrations on growth, yield and nitrate content in leaf lettuce plants in hydroponics. Seeds of lettuce cv, "Samsunjokchukmyon" were planted on April 29, and seedlings were planted on June 2, and were cultured until July 5 in 1998. KCI and CaCl₂ were used as chloride source and their concentrations were 1, 2 and 4 me/L, respectively, in the lettuce standard nutrient solution for National Horticultural Research Institute(NHRI). Completely randomized design with 3 replications was used. Nitrate content and NR activity were measured 2 and 5 weeks after planting(WAP). The obtained results were summarized as the follows : Leaf weight per plant was difference from harvest dates and treatments, but total leaf weight was not significantly different among treatments. Number of leaves was higher in KCI 2 me/L, CaCl₂1 me/L and control at 2 WAP than the others, and was higher in KCI 1 me/L, and control at 3 WAP than others, and was higher in control at 5 WAP. Total number of harvested leaves was the highest in control with 14, which followed by KCI 2 me/L and CaCl₂1 me/L. Nitrate content was decreased by addition of chloride in nutrient solution. Nitrate content in the 3rd and 9th leaves was significantly decreased. NR activity was higher in control and CaCl₂ addition treatments, while KCI addition treatments reduced NR activity. However, no direct relationship with nitrate was observed. Growth characteristics such leaf length and leaf width were not significantly influenced by chloride addition.