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Jung Eek Son, Yil Jang and Jung Hyuk Seo

Supporting materials for rooting have a considerable influence on the growth and quality of in vitro plantlets. Various supporting materials (rockwool, perlite, vermiculite, and polyurethane) and nutrient supply cycles (12, 24, 36, and 48 hours) were examined to find the optimum conditions for photoautotrophic micropropagation of potato plantlets in the nutrient-circulated micropropagation (NCM) system. In the NCM system, nutrient solution was circulated between the culture vessel and the nutrient reservoir. A plug cell tray with 70 plantlets was placed inside. The number of air exchanges was 10 hours under forced ventilation. Nodal leafy cuttings of plantlets were cultured at CO2 concentrations (mol·mol-1)/PPF s (mol·m-2·s-1) of 350/80, 700/120, and 1500/250 on day 5-11, 12-18, and 19-28, respectively, for all treatments. All growth factors of in vitro plantlets grown for 28 days using rockwool, perlite and vermiculite were greater than those grown using polyurethane. Dry weight of plantlets grown using rockwool was eight times greater than those grown using polyurethane. The same results were obtained in the growth and survival percentages 14 days after transplanting to ex vitro conditions. Optimum nutrient supply cycles were 12, 24, and 48 hours when perlite, rockwool, and vermiculite were used as supporting materials, respectively. It was considered that the range of optimum nutrient supply cycle was affected by water retention characteristics of supporting materials. This study proved that the supporting material and the nutrient supply cycle were very important environmental factors in photoautotrophic mass propagation.

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Myung Min Oh, Young Yeol Cho, Kee Sung Kim and Jung Eek Son

To determine the adequate irrigation conditions in a nutrient-flow wick culture (NFW) system, the water contents of root media were analyzed with different wick lengths (2 and 3 cm), pot sizes (6-, 10-, and 15-cm diameter), and media compositions (mixtures of 5 peatmoss : 5 perlite and 7 peatmoss : 3 perlite). The growth of potted ‘New Alter’ kalanchoe (Kalanchoe blossfeldiana) in the NFW system was also compared with that of plants grown in other irrigation systems, such as nutrient-stagnant wick culture and ebb-and-flow culture. All factors, such as wick length, pot size, and medium composition, influenced the water content of the medium in the NFW system. Pots that included more peatmoss with a shorter wick could easily take up the nutrient solution. The water content of the media increased by more than 8% and 5% in 2- and 3-cm wick lengths within 15 minutes respectively. The fluctuation of water content became greater with a decrease of pot size in the NFW system. Kalanchoe plants grew well in the NFW system with four irrigations for 15 min per day each. The dry weight and leaf area of the plants were higher in the NFW system (4×) and considerably lower in the NFW system with two irrigations for 15 min per day each. Therefore, more precise irrigation is required in the NFW system than in other systems.

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Jung Eek Son, Sung Kyu Kim, Sung Bong Oh and Yin Ji Lu

The uptake of water and nutrient in potted plants is greatly affected by irrigation conditions, and it influences the plant growth. This study aimed to examine the correlations between basic environmental parameters and plant growth in potted plants (kalanchoe) and to develop the models for adequate irrigation control. Growth chambers were developed for the experiments, and four levels of photosynthetic photon flux (PPF) were treated by using different numbers of shading films and lamps. Kalanchoe blossfeldiana cv. New Alter, grown in the nutrient-flow wick culture (NFW) system, was used. The 7-cm pots were filled with a 7:3 mixture of peat moss and perlite medium (v/v). The initial water content was set at about 26%. A total of 150 pots and plants with different growth stage were prepared for 4 weeks. A wick [12 × 1 cm (L × W)] was used in each pot. Leaf areas of plants and surface areas of the medium were analyzed by a plant image analysis system. For measuring the water losses of plants and pots during the growth stage, the initial water content of the substrates was maintained at about 55%. Water losses were measured at 9, 11, 13, 15, and 17 hours for all experiment periods by using an electron balance. Two models were developed for estimating water losses by evapotranspiration and water intake by water absorption. Finally, a model for estimating water content in the medium was tried. Growth and environment parameters showed high correlations with transpiration and evaporation, respectively. There was an interactive effect of VPD and PPF on the change of evapotranspiration. The amount of absorption was increased by time and decreased with increase of initial water content.