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Steven J. Bergsten, Andrew K. Koeser, and J. Ryan Stewart

hydroponics. Hydroponic culture of seedlings has been found to be effective for screening for salinity tolerance in agaves ( Nobel and Berry, 1985 ), other species ( Munns and James, 2003 ; Shaheen and Hood-Nowotny, 2005 ), and for other forms of

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Noah J. Langenfeld and Bruce Bugbee

biological demand requires greater inputs of oxygen to sustain homeostasis ( Ben-Noah and Friedman, 2018 ). The nutrient solution of liquid hydroponics benefits from levels of DO close to saturation near 8 mg⋅L –1 . This promotes healthy root respiration and

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Alejandro R. Puerta, Suguru Sato, Yutaka Shinohara, and Toru Maruo

.1080/00221589.1984.11515216 Jones J.B. Jr 1997 Hydroponics: A practical guide for the soilless grower St. Lucie Press Boca Raton, Fla Lee, S.K. Kader, A.A. 2000 Preharvest and postharvest factors influencing vitamin C content of horticultural crops Postharvest Biol. Technol. 20 207

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Richard V. Tyson, Eric H. Simonne, Danielle D. Treadwell, James M. White, and Amarat Simonne

.R. Harper, J.K. Takeda, F. Wade, E.D. Summerfelt, S.T. 2000 Economic evaluation of hydroponics and other treatment options for phosphorus removal in aquaculture effluent HortScience 35 993 999 Adler

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Carl E. Niedziela Jr., Paul V. Nelson, Daniel H. Willits, and Mary M. Peet

Commercial recommendations exist for using short-term salt-shocks on tomato (Lycopersicon esculentum Mill.) to improve fruit quality. Six experiments were conducted to 1) assess the influence of nutrient concentration and short-term salt-shocks on fruit quality and yield and 2) identify a vegetative predictor of subsequent fruit quality. The first objective was addressed in three nutrient film technique (NFT) experiments (Expts. 1-3). Four treatments were applied: two maintained constant at two baseline concentrations (0.25X and 1X-commercial level) and two provided salt-shock periods of 30 min, twice daily. There were no effects of baseline concentration or salt-shocks on total number and weight of marketable fruit. Fruit quality was better at the 1X baseline concentration as observed by higher titratable acidity (Expt. 2), higher percent dry matter (Expts. 2 and 3), higher soluble solids concentration (Expt. 2), and lower pH (Expts. 2 and 3), however, weight per marketable fruit was lower (Expt. 2). Salt-shocks had little effect on fruit quality, refuting its commercial potential. Salt-shocks decreased fruit pH (Expts. 1 and 3). However, titratable acidity increased at the 0.25X level and decreased at the 1X level (Expt. 3). In Expt. 2, but not in Expt. 3, citrate concentration in the fifth leaf from the apex of young vegetative plants was correlated with subsequent fruit quality. Three additional experiments in static hydroponics with vegetative plants showed no significant differences in leaf citrate levels due to a single, short-term salt-shock. Thus, citrate is not a good predictor of fruit quality.

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Jae-Woo Soh* and Yong-Beom Lee

Experiments were carried out to determine nutrient management system for butterhead lettuce `Omega' and leaf lettuce `Grand Rapids' in nutrient film technique (NFT), and to develop a rapid and reliable program for recirculation solution. The effects of controlling solutions with UOSL (Leaf Lettuce solution of the Univ. of Seoul, Korea; NO3 -N 10.55, NH4 -N 1.02, P 2.0, K 6.7, Ca 3.5, Mg 2.0, SO4 -S 2.0 me·L-1; Fe 2.0, Cu 0.1, B 0.5, Mn 0.3, Zn 0.3, Mo 0.05 ppm) were studied by greenhouse with managing by distilled water (DW), managing pH and EC (CM), managing by nutrient solution analysis (MN), managing by nutrient solution with leaf analysis (ML). The CO2 assimilation, transpiration rate, relative chlorophyll contents, leaf color, fresh weight and dry weight were highest in MN control in the butterhead `Omega' and in MN and ML control in the leaf lettuces `Grand Rapids'. The highest relative growth rate (RGR) was in MN ML in the butterhead `Omega' but those wasn't in the leaf lettuce `Grand Rapids'. Calculation program of adjustable solution was based on the main works by Visual Basic 5.0. The developed program could select an automatic and passive process considering the type of fertilizers, run-off rate, nutrient concentration, and water volume, for calculation. All of them were done successfully by the fast and precise calculation program.

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Joo Hyun Lee, Yong-Beom Lee, and Kyu Sook Lee

Wasabi japonica plantlets were acclimatized in a hydroponic system to determine effective procedures. The plantlets were cultured on solid Murashige-Skoog medium with 3% sucrose. Shoots that formed roots were transplanted into hydroponic systems: 1) acclimatization in ebb-and-flow (EBB) for subirrigation (medium: granulated rockwool and coir); and 2) acclimatization in deep flow technique (DFT). The plantlets were acclimatized for 5 weeks under two irradiance treatments, 50 and 300 mmol·m-2·s-1. Photosynthetic capacity in high PPF was higher than that in low PPF during acclimatization. Electron transport rate from PS II (ETR) and biomass production increased significantly with increased light availability. The fresh weight, dry weight, and leaf area of plantlets in high PPF were higher than those in low PPF. In particular, the dry weight and ETR of the plantlets grown in high PPF increased more than twice as much as those in low PPF. At 50 mmol·m-2·s-1 PPF, growth indexes, such as number of leaves, leaf length, leaf width, leaf area, fresh weight, and dry weight, were higher in EBB (granulated rockwool) > EBB (coir culture) > DFT. At 300 mmol·m-2·s-1 PPF, those indexes were higher in DFT > EBB (granulated rockwool) > EBB (coir). The Wasabi japonica plantlets acclimatized in a hydroponic system also had a superior performance when they were transferred to the field.

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J.A. Anchondo, M.M. Wall, V.P. Gutschick, and D.W. Smith

Pigment and micronutrient concentrations of New Mexico 6-4 and NuMex R Naky chile pepper (Capsicum annuum L.) cultivars as affected by low Fe levels were studied under soilless culture. A custom-designed, balanced nutrient solution (total concentration <2 mm) was continuously recirculated to the plants potted in acid-washed sand (pot volume 15.6 L). Each set of plants from each cultivar received iron concentrations at 1, 3, 10, and 30 μm Fe as Fe-EDDHA. The pigments of leaves, green fruit, and red fruit were extracted with acetone and measured with a spectrophotometer. Surface color of green and red fruit was measured with a chromameter. Total concentrations of Fe, Cu, Zn, Mn, P, and K of leaf blades and red fruit were measured by inductively coupled plasma emission spectroscopy (ICP). Ferrous iron in leaf blades, and NO3-N in petioles also were determined. Iron nutrition level affected total leaf chlorophyll and carotenoid content at early season, and the level of these pigments in green fruit at second harvest. No differences in extractable or surface color of red fruit were found among iron treatments in the nutrient solution, despite variations in red fruit iron content, total foliar iron, and foliar ferrous iron. Higher levels of iron in the nutrient solution increased both ferrous and total iron of the leaves, but depressed foliar Cu and P. High iron supply also increased fruit iron, and decreased fruit Cu content. High iron levels in the nutrient solution were associated with higher concentrations of leaf pigments at early season and higher pigment concentration in green fruit.

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Paul R. Adler, Jayson K. Harper, Fumiomi Takeda, Edward M. Wade, and Steven T. Summerfelt

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Harold V. Koontz, Ralph P. Prince, and Wade L. Berry