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Sang Gyu Lee* and Chiwon W. Lee

The pattern of C14 carbohydrate translocation and distribution from source leaf to various plant parts in watermelon grown in the greenhouse and field was investigated. Seedling-grown plants were pruned to have two branches with only one of them carrying a fruit. When leaves at four different positions (on fruit-bearing node, on fifth node above and below it, and on fifth node from the base of the non-fruit-bearing stem) were exposed to 14CO, the distribution of C14 2 compounds to different parts (fruit, stem, leaf, root) of the plant varied. In all treatments, the fruit was the strongest sink, followed by stem, leaf and root tissues. The highest percentage of C14 photo-assimilates was transferred out of the source when the leaf borne on the fruit-bearing node was exposed to 14CO2 in both greenhouse and field grown plants. Translocation of C14 compounds from the leaves on the fifth node above and below the first fruit-carrying node was similar. Only 29% of C14 was transferred from the source leaf borne on the fifth node of the non-fruit bearing branch in the greenhouse, as compared to more than 46% of C14 from other source leaves. Accumulation of C14 in the root tissues was highest when source leaves were borne on the non-fruit bearing branch. In general, field-grown plants had higher percentages of C14 translocated as compared to greenhouse-grown plants.

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Sang Gyu Lee* and Chiwon W. Lee

The pattern of translocation and distribution of C14 labeled photo-assimilates in watermelon and tomato grown in the greenhouse and field was characterized. Each of the mature leaves of the plant at active fruit development stage was exposed to 14CO2 (20 μCi radio activity) for 40 min and the leaves, stems, fruit, and roots were harvested 3, 6, 9, or 12 hours after treatment. One half of the plants were grown under natural light and the other half in the dark during the experimental period. The activity of C14 in the dry tissues of the leaves, stems, fruits, and roots was determined, using a liquid scintillation analyzer. Both watermelon and tomato plants grown in the greenhouse and field contained C14 in all tissue types 3 hr after treatment, regardless of exposure to light or dark during the experimental period. Watermelon and tomato, respectively, transferred 22% to 61% and 9% to 26% C14 from the source leaf in 3 hours. Fruit tissues served as the strongest sink, with the highest percentages of C14 transfer in watermelon (99%) and tomato (90%) in plants grown in the field. The rate of C14 translocation was highest when plants were kept in the dark after 14CO2 feeding. In general, total translocation of C14 compounds from the source leaf was higher in watermelon than in tomato plants. For both watermelon and tomato, most field-grown plants showed a higher rate of C14 translocation as compared to greenhouse grown plants for a given period of time.

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Sang Gyu Lee* and Chiwon W. Lee

The relationship between source leaf position and the photo-assimilate translocation and distribution was characterized for tomato (Lycopersicon esculentum Mill.) grown in the greenhouse. Three different positions of source leaf on the stem (first node above or below the first fruit cluster and fifth node above the first fruit cluster) were tested for their influence on 14CO2 assimilation and transfer to different parts of the plant. The leaves at the fifth node above the first fruit cluster transferred the highest (57%) proportion of C14 to other plant parts, followed by leaves borne on the first node below the first fruit cluster (50%), and the first node above the first fruit cluster (39%). In all treatments, fruits served as the strongest sink for C14, followed by stem, leaf, and root tissues. The leaf borne on the fifth node above the first fruit cluster transferred the largest amount of C14 to the second fruit cluster.

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Hee-Ju Lee, Sang-Gyu Lee, and Jung-Myung Lee

Increasing numbers of vegetables are being grafted in recent years and many different grafting methods, as well as grafting aids, have been developed and practiced among farmers as well as commercial plug seedling producers. For solanaceous crops, such as tomatoes, peppers, and eggplants, splice grafting at very young stages of development is recommended. Several types of grafting machines and/or robots are now available for commercial use. The presence of roots often slows down and reduces the efficiency of robot or machine grafting. Therefore, grafting with root-removed rootstocks is frequently used for grafting, mostly because of the grafting efficiency, especially in cucurbitaceous crops. The feasibility of producing grafted pepper plug seedlings using root-removed rootstock was investigated. After grafting, the seedlings were placed in pot soil in cell trays, usually 128-cell trays, and then placed in a conditioning room for subsequent rooting and graft union formation. Young pepper cuttings readily rooted in pot soils and the use of rooting substances greatly accelerated the speed of rooting. Even though rooting was delayed a few days in grafted seedlings, normal rooting took place in all graft combinations.

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Sung Eun Lee*, Sang Gyu Lee, and Chiwon W. Lee

The influence of plant density on yield of three confectionery seed pumpkin accessions was investigated under non-irrigated field conditions. Seeds of Golden Delicious (GD), open-pollinated Chinese snow-white seed (CS), and a selection from Austrian hull-less (HL) pumpkin were planted 30, 60, and 90 cm apart in rows that were 127 cm apart with seedlings thinned to one plant per hill. Plants were grown from 23 May to 18 Sept. One fruit per plant was harvested from five plants for each of the three replications. The number of seeds (and dry weight of seed) per fruit were 242 (59 g), 304 (87 g), and 334 (106 g), respectively, at 30, 60, and 90 cm spacing for GD. The number of seeds (and dry weight of seed) per fruit were 219 (108 g), 266 (108 g), and 258 (106 g), respectively, at 30, 60, and 90 cm spacing for CS. The number of seeds (and dry weight of seed) per fruit were 376 (76 g), 404 (94 g), and 304 (82 g), respectively, at 30, 60, and 90 cm spacing for HL. Highest seed yield was at 60 cm plant spacing for CS and HL, whereas GD produced highest seed yield at 90 cm plant spacing. The differences in total seed yield, seed size, and confectionery seed quality, as influenced by plant density and seed source, were also characterized.

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Hee-Ju Lee, Sang-gyu Lee, Changhoo Chun, and Jung-Myung Lee

Use of grafted seedlings is a practical method to overcome salt accumulation, deterioration of physicochemical properties of soil, and accumulation of soil-borne pathogen that farmers, as well as commercial plug seedling producers, in Korea mainly adapted. Graft-take, subsequent growth, and quality characteristics of grafted hot pepper (Capsicum annuum L.) seedlings composed of three scions and 10 rootstocks were investigated. `Manita', `Chungyang', and `Nokkwang' were cultivars of scions used—they are the major hot pepper cultivars in Korea. The ten rootstock cultivars can be categorized into three groups: cultivars specially bred for rootstocks (`Konesian Hot', `PR-380', `R-Safe', and `Tantan'); cultivars recently bred in NHRI, Korea with the potential to be rootstocks (`Wonkwang1' and `Wonkwang2'); and cultivars originally bred for fruit harvest, but used as rootstocks due to their tolerance to soil-borne pathogens (`Kataguruma', `PR-Data', `PR-Gangza', and `PR-Power'). All the plants were treated with 5 mg·L-1 diniconazole solution 2 weeks after grafting and were soaked into 1.4% salt solution for 48 hours about 5 weeks after grafting. All the grafted seedlings showed feasible growth, including normal flowering and fruit set, and any symptoms of phytophthora blight and anthracnose were not found during 17-day-long experiment. Seedlings grafted onto `Tantan' rootstock showed stronger tolerance to high salt concentration than those grafted onto other rootstocks. Use of some, such as `Wongang 1', `PR-Data' and `Kataguruma', was alleviated the salt-induced growth inhibition.

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Reza Salehi, Abdolkarim Kashi, Jung-Myung Lee, Mesbah Babalar, Mojtaba Delshad, Sang-Gyu Lee, and Yun-Chan Huh

Photosynthetic characteristics, concentrations of mineral elements in xylem sap, and some vegetative traits of ‘Khatooni’ melon were compared with those of melons grafted onto three Cucurbita rootstocks cvs., Ace, Shintozwa, and ShintoHongto, and trained with three methods: T1) no pinching and fruit thinning; T2) pinched to produce two lateral branches; and T3) pinched to two branches and all the flowers and lateral branches from lower nodes thinned. Internal CO2 and water use efficiency varied with rootstocks. Stem diameter of scions, aerial fresh and dry weights, mean fruit weight and yield, electric conductivity, pH, and sap volume per plant of grafted plants were higher in grafted melons than in the nongrafted ones. These traits were unaffected by training methods. Mineral concentrations varied considerably depending on the rootstocks and training methods used. Xylem sap collected from the decapitated stem base of grafted melons trained with T2 and T3 methods contained a higher amount of mineral ions, especially NO3 , PO4 3−, and K+, than did the sap from own-rooted plants. The increase in the mineral levels in sap resulting from grafting was most apparent in ‘Khatooni’ grafted onto ‘ShintoHongto’ rootstock.

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Yun-Chan Huh, Du-Hyun Kim, Sang-Gyu Lee, Kyoung-Sub Park, Dong-Kum Park, Young-Hoe Woo, and Jung-Myung Lee

Growth response of `Sambok Honey' watermelon grafted onto different rootstocks, including four Citrullus rootstocks and three other cucurbitaceous rootstocks, was evaluated at low and normal temperature regimes. Marked reduction in plant growth rate was observed in plants grown at low temperatures as compared to those grown at normal or optimal temperatures. Relative growth reduction rates were 40% to 48% for vine length, 39% to 51% for total leaf area, 37% to 60% for shoot fresh weight, and 50% to 79% for shoot dry weight, respectively. Watermelon rootstock PI 482322 showed comparable plant growth as the most popular rootstock (Shintozwa pumpkin) even at low temperatures. `Sambok Honey' watermelon grafted onto watermelon hybrids `PI 271969 × PI 296341' and `PI 271769 × Calhoun Gray', showed comparable plant growth as FR Dantos bottle gourd rootstock. Index of growth ability at low temperature (IGALT), which was calculated on the basis of reduced rate of vine length, dry weight, and leaf area, was comparatively high in C. martinezii, Shintozwa, PI 482322, and `PI 271769 × PI 296341' rootstocks (50% or higher) and lowest in own-rooted `Sambok Honey' or in watermelon plants on `Knight' rootstock. Watermelon hybrids `PI 271969 × PI 296341' and `PI 271769 × Calhoun Gray' exhibited better or at least comparable growth at low temperatures as compared to `FR Dantos', thus confirming the feasibility of using watermelon rootstocks even in winter greenhouse conditions.

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Sang Gyu Lee, Dong Kum Park, Kyung Sup Park, Yun Chan Heo, Yoon Ah Jang, Kwan Dal Ko, and Chiwon W. Lee

The fruits of pumpkin are good material for soup and a very popular side dish in Korea. The purpose of this study was to investigate how number of fruit set per plant (2, 3, or 4 fruit) affected production of dried seed and fruit yield. `Golden Delicious' (GD) and hull-less (HL) pumpkins were planted 60 cm apart in 200-cm rows. Production of dried seed per hectare (11,000 plants) were 1985, 2193, and 2074 kg, respectively, at 2-, 3-, and 4-fruit set per plant for GD. The fruit yield per hectare (11,000 plants) was 58,360 kg for 2-fruit set treatment, 74,680 kg for 3-fruit set, and 73,240 kg for 4-fruit set per plant for GD. The production of dried seed per hectare (11,000 plants) was 535, 603, and 545 kg, respectively, for 2-, 3-, and 4-fruit set per plant for HL. The fruit yield per hectare (11,000 plants) was 28,200 kg for 2-fruit set treatment, 44,660 kg for 3-fruit set, and 39,200 kg for 4-fruit set per plant for HL. The highest production of dried seed and fruit yield were for 3-fruit set per plant for GD and HL. Differences in production for dried seed and fruit yield, as influenced by number of fruit set per plant, were also characterized.