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Juan Carlos Diaz-Perez, W. Keith Jenkins, Dharmalingam Pitchay, and Gunawati Gunawan

microorganisms, resulting in higher rates of net ammonification than net nitrification ( Britto and Kronzucker, 2002 ). Seed germination and seedling establishment can be inhibited by ammonia ( Cook, 1962 ). Symptoms of ammonia toxicity appear when external

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

recirculating aquaculture systems is the biofiltration of fish waste ammonia through nitrification to maintain fish tank water quality ( Gutierrez-Wing and Malone, 2006 ; Masser et al., 1999 ). This is necessary because 10% of the protein in fish feed becomes

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Guiwen W. Cheng and Patrick J. Breen

Abbreviations: DAA, days after anthesis; PAL, phenylalanine ammonia-lyase. Oregon Agricultural Experiment Station Technical Paper no. 9476. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal

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Danijela Janjanin, Marko Karoglan, Mirjana Herak Ćustić, Marijan Bubola, Mirela Osrečak, and Igor Palčić

Butzke (1998) . NH 4 + content (mg·L −1 ) was measured with Megazyme Ammonia Assay Kit and procedure (Megazyme, Chicago, IL), according to the method of Bergmeyer and Beutler (1990) , using ultraviolet spectrophotometer (SPECORD 400). YAN (mg·L −1 ) was

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D.C. Fare, C.H. Gilliam, G.J. Keever, and J.T. Touchton

Water samples containing 0, 2.5, 10.0, or 20.0 ppm nitrate and ammonia were evaluated under 3 temperatures (0, 6, 20C) plus or minus sulfuric acid (36N) for changes in concentration. Ammonia and nitrate levels were measured 0, 1, 2, 4, 8, 16, 24, and 32 weeks after storing. Response to storage conditions was the same regardless of acid or concentration of ammonia or nitrate. Nitrate concentrations in the storage locations were similar for the first 2 weeks. Afterwards, treatments stored at room temperature fluctuated from initial standards. With ammonia, frozen samples had the greatest deviation from initial standards during the first 4 weeks. By week 24, ammonia samples stored at room temperature had exceeded acceptable deviations from the standards. Nitrate and ammonia samples held in refrigeration had the least fluctuation during the 32 week storage period.

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Mark A. Ritenour, Teofilo Ng-Sanchez, and D. Frank Kelsey

Quaternary ammonia (QA) has been used on equipment and fruit bins in Florida to reduce the risk of spreading citrus canker. This study was initiated to understand the cause of a previously unknown peel injury believed to be associated with QA residues. Symptoms of QA injury on `Marsh' grapefruit (Citrus paradisi) usually developed within 24 to 36 h of contact with QA and ranged in severity from very slight discoloration to severe, dark brown, necrotic peel tissue that collapsed to form large sunken areas. Placing fruit in 10 mL (0.34 floz) of ≥100 mg·L-1 (ppm) fresh QA solution caused moderate to severe peel injury. Drying the QA solutions on polystyrene petri dishes and then redissolving the residue with 10 mL deionized water before fruit contact resulted in essentially the same degree of peel injury as contact with fresh QA solutions. Peel injury on early (November) or late-season (April) grapefruit also occurred when fruit were placed on a thin film of QA solution left on polystyrene petri dishes after dipping the dishes in ≥300 mg·L-1 QA solutions or if fruit themselves were dipped in QA solutions ≥500 mg·L-1. No significant peel injury occurred when dipping solutions contained only water with 200 mg·L-1 chlorine, 0.025% (v/v) Triton N-101, or a combination of both.

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Richard V. Tyson, Danielle D. Treadwell, and Eric H. Simonne

concentrations found in hydroponic systems ( Rakocy, 1997 ). The aquaponic nitrogen (N) cycle ( Fig. 1 ) is of particular interest. Fish produce ammonia (NH 3 ), some of which ionizes in water to form ammonium (NH 4 + ). Nitrifying bacteria in biofilters convert

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James E. Ells, Ann E. MeSay, and Stephen M. Workman

Chopped alfalfa (Medicago sativa L.), alfalfa hay extract, and ammonium hydroxide produced free ammonia in media and inhibited both germination and seedling growth of cucumber (Cucumis sativus L.). Toxic levels of ammonia were not produced by the quantities of manure added to the media. Alfalfa extract enhanced cucumber seedling growth in sand medium while inhibiting growth in sand-soil media. This difference is attributed to a reduced level of microbial activity in the sand. With higher levels of microbial activity, rapid decomposition of the extract may have resulted in a burst of ammonia evolution that proved damaging to cucumbers. The natural buffering capacity of the soil medium apparently mitigated the effects of the ammonia. Ammonium hydroxide, which did not depend on microbiological activity to release ammonia, proved lethal to cucumbers grown in sand. A diminished effect on growth was observed as the cation exchange capacity of the medium increased. Because high levels of alfalfa hay and ammonium hydroxide were required to produce toxic levels of ammonia in soil, it is unlikely that cucumbers would be harmed under normal field usage of alfalfa hay.

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C. Peter Romaine and Laurie Raid

Commercial strains of Agaricus bisporus (Lange) Imbach that were grown in vitro at 32C for 4 to 5 weeks on a medium containing 250 μg amantadine/ml followed by hyphal tip-culturing showed an enhanced tolerance of ammonia in the compost during cropping trials. Yield of mushrooms by a treated off-white strain (GSP-18) and a treated white strain (Marlowe-503) was higher in composts with elevated levels of ammonia (0.11% to 0.27%) than that of the untreated cultures. Tolerance was related to the ability of the treated cultures to grow vegetatively in the ammonia-enriched compost. Tolerance was expressed by the cultures for at least 14 months following induction.

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Phillip N. Miklas, Kenneth F. Grafton, and Phillip E. McClean

We investigated the partial physiological resistance (PPR) of common beans (Phaseolus vulgaris L.) to white mold disease caused by Sclerotinia sclerotiorum (Lib.) deBary. The activity of phenylalanine ammonia-lyase (PAL) was measured in detached stems inoculated with a growing mycelium of the pathogen. Noninoculated detached stems and whole plants were included as controls. Five bean cultivars-Upland, Bunsi, Sierra, UI-114, and Montcalm-and one breeding line-NY 5394-were tested; all varied in PPR to white mold disease. Greater PAL activity in the resistant NY 5394 than in the susceptible `Upland' suggests that PAL activity may be involved in the PPR of common beans to S. sclerotiorum.