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Charis-Konstantina Kontopoulou, Sofia Giagkou, Efthalia Stathi, Dimitrios Savvas, and Pietro P.M. Iannetta

, very little research work has adequately addressed the impact of Rhizobium inoculation on N 2 fixation and yield performance in soilless cultivation of common bean. Jebara et al. (2001) inoculated five common bean lines grown in two hydroponic

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Stephanie E. Burnett, Donglin Zhang, Lois B. Stack, and Zhongqi He

primary objective of this research was to determine how fan flower morphology is impacted by various P concentrations under a constant pH. To ensure ease of pH adjustment, fan flower plants were grown hydroponically, not in typical container substrates. A

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Jeffrey M. Hamilton and Jorge M. Fonseca

hydroponically grown salt-sensitive plants Plant Soil 42 717 721 Podsedek, A. 2007 Natural antioxidants and antioxidant capacity of Brassica vegetables: A review LWT-Food Sci.Technol. 40 1 11 Reddy, A

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Eun Young Yang*, Hye Jin Lee, and Yong-Beom Lee

The application of a closed hydroponic system for rose poses some horticultural problems. The nutrient uptake by the plants changes constantly depending upon environmental conditions and growing stages, which results in the imbalanced composition of the drained solution and aggravates root environmental conditions. This research was aimed to observe the effect of mineral nutrient control method on the nutrient solution management in a closed hydroponic system. Single-node cutting rose `Versillia' was grown in aeroponics and DFT system and was irrigated with the nutrient solution of the Univ. of Seoul (NO3 -N 8.8, NH4 -N 0.67, P 2.0, K 4.8, Ca 4.0, and Mg 2.0 me·L-1). Recirculated nutrient solution was managed by five different control method: macro- and micro-element control in aeroponic system (M&M); macroelement control in aeroponic system (M); nutrient solution supplement in aeroponic system (S); electrical conductivity (EC) control in aeroponic system (EC-A); EC control in deep flow technique system (EC-D). In the EC control method, the concentration of NO3 -N exceeds optimal range whereas P and Mg decreased at the later stage of plant growth. The overall mineral nutrient content increased with S. On the other hand, the nutrient content of root environment was maintained optimally with M&M and M.

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Xuan-Chun Piao, Debasis Chakrabarty, Eun-Joo Hahn, and Kee-Yoeup Paek

In vitro nodal cuttings of potato (Solanum tuberosum L.) `Atlantic' and `Russet Burbank' from bioreactor culture were hydroponically cultured for 28 days using a deep flow technique (DFT) system. The response of plant growth and photosynthesis to different levels of solution electrical conductivity (EC; 0.08, 0.15, 0.22 and 0.36 S·cm-1) and pH (3, 4, 5, 6 and 7) were studied. The best growth, characters of shoot length, total shoot and root fresh and dry weight, were obtained in nutrient solution of pH 6.0 and EC 0.15 S·cm-1 for `Atlantic', while pH 7.0 and EC 0.15 S·cm-1 were found to be best for `Russet Burbank'. Plantlet growth was reduced by low solution pH (3.0) and high EC level (0.36 S·cm-1). Photosynthetic rate, stomatal conductance, and transpiration rate were also found to be affected by EC levels. Down regulation of photosynthesis, as indicated by chlorophyll fluorescence results, were observed when potato plantlets were cultured under nutrient solution of higher EC level. Plantlet growth and photosynthetic rate increased as photosynthetic photon flux (PPF) levels increased from 50 to 250 μmol·m-2·s-1. Particularly, increasing PPF level had a more distinctive effect on plantlet growth than CO2 enrichment condition. It was apparent from this study that nutrient solution of pH 6.0 and 0.15 S·cm-1 EC in combination with high PPF level (250 μmol·m-2·s-1) were suitable for hydroponic culture of potato plantlets as it would maximize net photosynthetic rate, and achieve the highest growth rates.

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Byoung Ryong Jeong and Chi Won Lee

Ageratum and salvia were grown in hydroponic solutions containing either NH4 +, NO3 -, or both NH4 + and NO3 - with or without Cl- to study changes in solution pH and ion uptake rate. pH of both NH4 + and NH4 + + NO3 - solutions was steadily decreased as time passed. A drop in pH front 6.50 to 3.57 within 3 days was recorded with NH4 +. The pH changes were also affected by the presence of Cl-. The NO3 - treatment maintained its initial solution pH over time regardless of the presence of Cl-. pH change by ageratum was greater than that by salvia, especially when plants were in NH4 + + NO3 - solution. N uptake was maximum in NH4 + + NO3 - solution with Cl-. Uptake of NO3 - was suppressed by NH4 +, but NH4 + uptake was not affected by NO3 -. NH4 + and NO3 - counteracted each other in influencing the Cl- uptake. Uptake of other ion was also affected by plant species as well as N source and Cl-. In ageratum transpiration rate was lowered by Cl- in both NH4 + and NO3 - treatments.

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M.D. Erdman, S.C. Phatak, and H.S. Hall

Abstract

Arrowroot (Maranta arundinacea L.) was cultivated in Tifton, Ga., under various fertilization regimes (0, 220, 449, 668, and 897 kg·ha−1 of a 10N–4.4P–8.3 mixture), plant densities (3450, 6900, 13800, 20700, and 27600 plants ha−1), in solutions of half-strength Hoagland's solution, unfermented dairy waste solution, and anaerobically fermented dairy waste solution, or in solution-supplemented soil studies. Optimum starch yield ha−1 occurred at 220 kg·ha−1 fertilizer treatment. Calculated starch yield of 2770 kg·ha−1 could be obtained at a planting density of 20700 plants ha−1. Growth of aerial biomass was demonstrated in solution culture; however, rhizomes were not produced. Biomass and starch yields of arrowroot cultivated in solution-supplemented soil were comparable when Hoagland unfermented or fermented solutions were used.

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A.P. Papadopoulos, S. Pararajasingham, and X. Hao

Experiments were carried out to evaluate two salts, K2SO4 and NaCl, as materials to supplement the electrical conductivity (EC) of the basic nutrient solution in nutrient film technique (NFT). The effects of these materials on the growth, yield and fruit quality of greenhouse tomato (Lycopersicon esculentum Mill.) grown by NFT were quantified. These effects were tested by increasing the recirculating solution EC from a base value of 1500 μS·cm-1 to that suitable for the crop growth stage with normal feed (macronutrients), 0.38 m (0.53 lb/gal) K2SO4 or 1.14 m (0.55 lb/gal) NaCl, at a common pH of 6.2. In 1995 and 1996, there were no significant effects of the treatments on crop growth. In 1995, the early marketable yield was significantly lower when K2SO4 was used but the yield at the end of the season did not differ among the treatments. Furthermore, with K2SO4, the proportion of grade #1 fruit in early total yield was lower than in the control, while, fruit biomass content was higher than in the NaCl treatment. In 1996, the cumulative marketable fruit weight was unaffected by the treatments. A trend toward high number of large grade fruit occurred with the NaCl treatment. The pH and EC of the fruit homogenate were favorably affected by the NaCl treatment. Adding K2SO4 or NaCl in partial substitution of macronutrients in the recirculating solution may have a role in NFT systems in not only reducing environmental pollution (from nitrates and phosphates) and fertilizer costs, but also in improving fruit quality and, therefore, profit margins.

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Bruce Bugbee and John W. White

Abstract

The effect of root-zone temperature on young tomato plants (Ly copersicon esculentum Mill. cv. Heinz 1350) was evaluated in controlled environments using a recirculating solution culture system. Growth rates were measured at root-zone temperatures of 15°, 20°, 25°, and 30°C in a near optimum foliar environment. Optimum growth occurred at 25° to 30° during the first 4 weeks of growth and 20° to 25° during the 5th and 6th weeks. Growth was severely restricted at 15°. Four concentrations of gibberellic acid (GA3) and kinetin were added to the nutrient solution in a separate trial; root-zone temperature was maintained at 15° and 25°. Addition of 15 μm GA3 to solutions increased specific leaf area, total leaf area, and dry weight production of plants in both temperature treatments. GA3-induced growth stimulation was greater at 15° than at 25°. GA3 may promote growth by increasing leaf area, enhancing photosynthesis per unit leaf area, or both. Kinetin was not useful in promoting growth at either temperature.

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Charlie Garcia and Roberto G. Lopez

Supplemental lighting is required for the production of high-quality vegetable transplants in greenhouses when the photosynthetic daily light integral (DLI) is low. Light-emitting diodes (LEDs) are a promising alternative to high-pressure sodium (HPS) lamps. However, there are a limited number of studies that have evaluated how LED supplemental lighting spectral quality beyond blue (B) and red (R) radiation influences plant growth and development. Seeds of hybrid greenhouse seedless cucumber ‘Elsie’ (Cucumis sativus), tomato ‘Climstar’ (Solanum lycopersicum), and pepper ‘Kathia’ (Capsicum annuum) were sown and placed into a dark growth chamber until radicle emergence. Seedlings were grown in a greenhouse at a 25 °C constant temperature set point and under five lighting treatments. The supplemental lighting treatments delivered a total photon flux density (TPFD) of 120 μmol·m−2·s−1 for 16 h·d−1 based on an instantaneous threshold from HPS lamps or LEDs [three treatments composed of B (400–500 nm), R (600–700 nm), white, and/or far-red (FR; 700–800 nm) LEDs], and a control that delivered 25 μmol·m−2·s−1 from HPS lamps (HPS25). The LED treatments defined by their wavebands (TPFD in μmol·m−2·s–1) of B, green (G, 500–600 nm), R, and FR radiation were B20G10R75FR15, B25R95, and B30G30R60; whereas the HPS treatments emitted B7G57R47FR9 (HPS120) and B1G13R9FR2 (HPS25). Generally, cucumber, pepper, and tomato transplants under B30G30R60 and HPS120 supplemental lighting had the greatest stem diameter. Fresh weight and leaf area of all three species was greater when G radiation replaced R or B radiation. For example, leaf area and fresh weight of cucumber, tomato, and pepper increased (by 33%, 22%, and 49%; and 35%, 14%, and 56%, respectively) for plants under B30G30R60 supplemental lighting compared with plants under B25R95 supplemental lighting. The most compact cucumber and pepper transplants were those grown under B25R95 supplemental lighting, and the most compact tomatoes were those grown under the HPS25 (control) and B25R95 supplemental lighting. Tomato transplants under treatments providing ≥30 μmol·m−2·s−1 of G radiation had an increased incidence of leaf necrosis. From this study, we conclude that plant responses to supplemental lighting quality are generally genera-specific, and therefore high-wire transplants should be separated by genera to optimize production and quality. However, additional studies are required to provide complete LED supplemental lighting recommendations.