• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.3
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• pp.163-171
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• 2017

Effects of different packaging methods for maintaining the shelf life and postharvest quality of iceberg lettuce (Lactuca sativa L.) were studied after harvesting in summer season. Lettuce heads were packaged in plastic crate with or without different films such as (A) Individual lettuce head sealed packaging with linear low density polyethylene (LLDPE) film; (B) Packaging lettuce head in plastic crate and wrapped with LLDPE film; (C): Individual lettuce head sealed packaging with perforated high density polyethylene (HDPE) film; (D) Packaging lettuce head in plastic crate and wrapped with perforated HDPE; and (E) Packaging lettuce head in plastic crate without any film (control), and stored at $2^{\circ}C$ for 35 days. Several quality parameters such as fresh weight loss, SPAD (soil & plant analyzer development) meter value, respiration rate, moisture content and appearance of lettuce were investigated. The lettuce wrapped with individually-sealed LLDPE film showed the lowest weight loss and the highest SPAD value rendering the best appearance index among the treataments throughout the three-week storage period at $2^{\circ}C$. Extending the freshness of iceberg lettuce during low temperature storage will definitely increase the salability potential in the domestic market even during summer season.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.1
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• pp.57-61
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• 1992

For testing salts effect on seed germination, nitrogen solutions($(NH_4)_2SO_4$, $NH_4NO_3$, $KNO_3$, $Mg(NO_3)_2$, $Ca(NO_3)_2$, $(NH_2)_2CO$) were treated to chinese cabbage(Brassica rape L.) and lettuce(Lactuca sativa L.) seeding on the quartz sand bed given a tilt to wet by dripping. Electrical conductivities (mS/cm) increased with direct proportion by equivalent gram-molecular weight at $(NH_4)_2SO_4$ and $KNO_3$, $NH_4NO_3$, but those of Mg and Ca salt remained 1 1/2 times higher. And urea solution never showed EC at all. $(NH_4)_2SO_4$ solution appeared to have value of EC with 1.37 times as high as that of $KNO_3$ and it was in order of $(NH_4)_2SO_4>NH_4NO_3>KNO_3>Ca(NO_3)_2>Mg(NO_3)_2$ comparing with same percentage solution. Application of $Mg(NO_3)_2$ and $(NH_4)_2SO_4$ among 6 salts resulted in a severe decreas in germination of both crops, and $NH_4NO_3$ showed light inhibition in comparison to $KNO_3$. Urea showed little effect on germination as the same as $Ca(NO_3)_2$ and $KNO_3$ solution at low concentrations, but the latter two salts reduced germination remarkably at high concentrations. It is likely to show that germination inhibition is not affected by salt salanity but by the sort of salts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.3081-3088
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• 2013

Phenolic contents and antioxidant activities were determined in the water and ethanol extracts from six species of edible seaweeds, Phaeophyceae (Laminaria japonica, Hizikia fusiformis and Undaria pinnatifida), Rhodophyceae (Porphyra tenera and Gracilaria verrucosa) and Chlorophyceae (Ulva lactuca). The highest extraction yield was observed in water extract (pH 8.0) of G. verrucosa (44.23 %) and phenolic content was the highest in ethanolic (75 %) extract of H. fusiformis (52.82 ${\mu}g/mg$). 25 % ethanolic extract from U. lactuca was found to have the highest DPPH radicals scavenging activity(19.29 %) and superoxide anion scavenging activitiy was higher in water extract (pH 8.0) from H. fusiformis (81.20 %) than that other seaweeds. Phenolic contents were strongly correlated with antioxidant activity in the six edible seaweeds extracts ($R^2$=0.852). Taken together, these results indicate that H fusiformis may be a excellent source for development of natural antioxidants.

• Korean Journal of Weed Science
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• v.8 no.3
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• pp.265-272
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• 1988

This experiment was carried to investigate the germination pattern in relation to temperatures and lights, and the emergence pattern in relation to seeding depths, lights and the alpha amylase activity of Youngia sonchifolia, Lactuca indica var. laciniata, Ixeris dentata var. albiflora and Ixeris polycephala. In Y. sonchifolia, the optimum germination temperature was $25^{\circ}C$, the optimum seeding depth to emerge was 0 mm and it could emerge in 0-5mm. In L. indica var. laciniata under cool storage, the optimum germination temperatures were $19^{\circ}C-28^{\circ}C$, the optimum seeding depth was 5mm and it could emerge in 0-20mm. In L. indica var. laciniata under room storage, the optimum germination temperature was $25^{\circ}C$ the optimum seeding depth was 5mm and it could emerge in 0-10mm. In I. dentata emerge was and 0mm and it could emerge in 0-5mm. In I. polycephla, the optimum temperatures were $16^{\circ}C-19^{\circ}C$, the optimum seeding depth to emerge was 0mm and it could emerge in 0-5mm. The alpha amylase activity was lower Y. sonchifolia, L. indica var. laciniata and I. dentata var. abiflora than barley cultivar Dongbor#1. And the increased pattern of alpha amylase activity was likely to it of germination rate.

• Korean Journal of Food Science and Technology
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• v.23 no.2
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• pp.133-140
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• 1991

Weight-loss, general-appearante, yellowing, and compositions such as chlorophyll, carotenoid, vitamin C and nitrate, were studied to investigate the influence of pre-(cultivar and growing season) and post-(low-temperature and high-density polyethylene film packaging) harvest factors on the shelf-life and quality of leaf lettuce(Lactuca sativa L). Weight-loss was reduced by the treatment of high-density polyethylene film packaging, and more at $0{\sim}1^{\circ}C$ than $4{\sim}5^{\circ}C$. Leaf-lettuce grown in Winter lost less fresh weight than that grown in Autumn. In experiment on difference between cultivars, the reduction of weight-loss in 'Cheongchima' lettuce was somewhat significant than that in 'Jeokchukmyeon' lettuce. The tendency of changes in general appearance was similar to that of weight-loss. The yellowing of leaf lettuce during the storage was caused by chlorophyll degradation. Vitamin C content before the storage was 128.0 mg/100 g FW. in lettuce grown in Winter, 123.8 mg/100g FW. in that grown in Autumn, and more 'Cheongchima' lettuce than 'Jeokchukmyeon' lettuce. In all treatment, vitamin C content decreased rapidly, and this tendency was more obvious at $4{\sim}5^{\circ}C$ than $0{\sim}1^{\circ}C$. The nitrate content of 'Jeokchukmyeon' was 3812.6 ppm and that of 'Cheongchima' was 2855.6 ppm before the storage. Nitrate content decreased more at $4{\sim}5^{\circ}C$ than $0{\sim}1^{\circ}C$ during the storage.

• Research in Plant Disease
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• v.13 no.1
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• pp.66-70
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• 2007

During 1997 and 1998, a new disease of lettuce (Lactuca sativa) was observed on greenhouse-grown plants in Kwangju and Kwangmyung. Lesions on leaves were irregular, small, pale green to black, water-soaked, and 2 to 5 mm in diameter, Coalescing lesions sometimes caused defoliation of older leaves. Isolations made from diseased leaves on yeast extract dextrose calcium carbonate agar yielded nearly pure cultures of a yellow pigmented bacterium typical of a xanthomonad. Two bacterial strains (SL0246 and SL1352) were purified and used for further tests. Pathogenicity of strains was confirmed on 5-week-old lettuce plants injected with bacterial suspensions containing $10^8$ cfu/ml of phosphate buffered saline. The representative Xanthomonas strains isolated from lettuce were compared with a reference strain X. campestris pv, vitians for fatty acid profiles and metabolic fingerprints using GN2 microplate, showing that all outcomes were indistinguishable between the representative and reference strains. This is the first report of bacterial leaf spot and dry rot of lettuce in Korea.

• Horticultural Science & Technology
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• v.32 no.3
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• pp.330-339
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• 2014

Growth and anthocyanins of lettuce (Lactuca sativa L., 'Mid-season') grown under LED lamps with blue light in the range of 430-470 nm or with red light in the range of 630-670 nm were analyzed in this study. Cool-white fluorescent light was used a s the control. P hotosynthetic photon flux, p hotoperiod, air temperature, relative humidity, and $CO_2$ concentration in a closed plant production system were $201{\pm}2\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 16/8 hours (day/night), $22/18^{\circ}C$, 70%, and $400{\mu}mol{\cdot}mol^{-1}$, respectively. At 21 days after light quality treatment, growth characteristics and anthocyanins content of lettuce as affected by the peak wavelength of blue or red LED were significantly different. Among peak wavelengths treated in this stusy, R1 treatment (peak wavelength 634 nm) and R6 treatment (peak wavelength 659 nm) were effective for increasing leaf width, leaf area, shoot fresh weight, and photosynthetic rate of lettuce. B5 treatment (peak wavelength 450 nm) and B4 treatment (peak wavelength 446 nm) increased the anthocyanins concentration and chlorophyll content in lettuce leaves, respectively. Anthocyanins in lettuce leaves increased linearly with decreasing hue value of leaf color and with increasing SPAD value of lettuce leaves. From these results, it was concluded that the red LED with peak wavelengths of 634 nm and 659 nm and the blue LED with peak wavelengths of 450 nm can be used as potential light spectra for increasing the yield and anthocyanins accumulation of leafy vegetable.

• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.128-138
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• 1985

This study was conducted to elucidate the shelf-life and quality changes in relation to biochemical components in leaf lettuce (Lactuca sativa L.). The shelf-life of leaf lettuce at room temperature was 2 to 3 days. But it was extended to 3 weeks by packaging in a 0.01 mm thick polyethylene film sack when stored at $3^{\circ}C$. The ascorbic acid contents of fresh leaf lettuce was 25 mg per 100 gram fresh weight. The acid at room temperature was almost destroyed after 4 days storage. But the contents of ascorbic acid at $3^{\circ}C$ maintained about 50 to 60% of the initial level in packaging of polyethylene film sack after 8 days storage. The content of chlorophyll was greatly decreased at room temperature but no significant changes were found at $3^{\circ}C$. The changes of total sugar and reducing sugar contents during storage were not very different between treatments. The contents of alkali soluble protein and free amino acid gradually increased in the treatments of polyethylene film sack packaging during storage in general, but the contents decreased after the increase in control treatment. Nucleic acid content, peroxidase and polyphenoloxidase activities were measured and discussed in relation to the leaf senescence.

• Journal of Life Science
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• v.27 no.4
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• pp.408-416
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• 2017

This research aimed to identify the diversity and the distribution of invasive alien plant species in the metropolitan city of Busan, South Korea. According to our results, we discovered 10 species of invasive alien plants distributed in Busan, demonstrating that this urban area has a high domestic plant diversity. A cluster analysis identified that the dominant communities of Aster pilosus, Lactuca serriola, Ambrosia artemisiifolia, Rumex acetosella and Solanum carolinense were highly similar in species composition. Different species of invasive alien plants tended to occur together in dominant communities, indicating their preference for shared habitats. The most extensively distributed species in Busan were Lactuca serriola (16 districts), followed by Ambrosia artemisiifolia (11 districts), Aster pilosus (11 districts) and Rumex acetosella (10 districts). The administrative districts with the most diverse invasive alien plants were Gangseo-gu (8 species) and Buk-gu (8 species), which are both areas with high human interference and diverse habitats. Additional environmental information was collected for these species' habitats in Busan. The results of this research can be used to assess the current status of invasive alien plants in Busan and can provide basic data useful for effectively controlling and preventing the spread of invasive plants.

• Journal of Distribution Science
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• v.16 no.8
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• pp.63-68
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• 2018

Purpose - Lettuce (Lactuca sativ L.) is one of the economically important vegetable crops, which worldwide market value is over 100 billion U.S. dollar. In Korea, about 89.7 kilo ton of lettuce was produced in 3400ha in 2016, recoded as No. 1 vegetable crop in domestic green house production. However, recently, domestic lettuce production and cultivation areas are all getting decreased. Thus, novel approaches are needed to be implemented to revive the production. Research design, data and methodology - In this review paper, we first prioritized the end-user traits which are imperative to positively stimulate the domestic lettuce market and discussed relevant genomics strategies. Especially, we assessed a possibility whether school meal program would be a potential niche market. Results - The genomics technologies, which become widely applied in the crop biotechnology since 2008 when next generation sequencing method was developed, may be a good solution in the crop improvement, efficiently gathering valuable information of agriculturally useful traits. Significantly, in lettuce, the high quality whole genome sequence, based on Lactuca sativa cv. Salinas, is publically available and this genomics platform, thus, would be implemented in lettuce breeding program to innovate relevant end-user traits both for the farmers and customers, including the disease resistance to the Fusarium wilt, productivity under hot weather conditions, various nutritional qualities and so forth. These improvements will boost domestic lettuce industries in the near future. Conclusions - Due to the nutritional distinctions comparing to the western style lettuces, domestic leaf lettuces could be one of the important vegetables in the school meal programs. To make it happen, we would better devise diverse recipes to make a salad with it, instead of only using as a wrap vegetable. Meanwhile, novel lettuce varieties need to be developed, which are favorable to the students and also easy to be handled with while processing. Overall, to achieve international competence in the lettuce industries, we need to create elite lettuce varieties that satisfies domestic farmers as well as customers, suitable to various niche markets, such as school meal program. Thus, efficient breeding programs using genomics approaches should be established in advance and careful monitoring on the preference of the related customers for a niche market be continued persistently.