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  • Author or Editor: Allen V. Barker x
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Abstract

Ethylene evolution was determined for tomato (Lycopersicon esculentum Mill.) plants grown under nutrient-deficient (N, P, K, Ca, Mg, S) conditions or under full nutrition with NH4 + or NO 3 in sand culture. Ethylene evolution increased for plants deficient in K, Ca, or Mg relative to that of plants grown on nutritionally complete solutions with NO 3 . Deficiency of N, P, or S did not stimulate ethylene evolution relative to that detected from plants grown with complete nutrition with NO 3 . Physiological stress from NH4 + nutrition produced enhancements in ethylene evolution that exceeded those due to deficiencies of macronutrients.

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Inhibitors of ethylene synthesis and action were used to alleviate ammonium toxicity in tomato (Lycopersicon esculentum Mill. `Heinz 1350') grown on ammonium-based nutrient solutions. Aminooxyacetic acid and Ag+ were effective in reducing ammonium toxicity, whereas Co+2 and salicylic acid were not. A hypothesis was developed to integrate ammonium accumulation and ethylene biosynthesis into a mechanism for expression of plant injury from environmental stresses.

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For optimum plant growth in containers, adequate plant nutrition is essential. Objectives of this research were to determine the optimum fertilization of tomatoes (Lycopersicon esculentum Mill.) in a peatbased medium and to assess plant nutrition by plant and media analysis. Tomato seedlings ('Heinz 1437') were transplanted (one plant per pot) into 2-L pots filled with a peat-based medium. The medium was fertilized with a progressive array of soluble fertilizers to supply N at 0, 50, 100, 150, or 200 mg·L-1 of solution with concomitant proportional increases of other macronutrients with each increase in N (P at 0, 10, 20, 30, or 40; K at 0, 40, 80, 120, or 160; Ca at 0, 50, 100, 150, or 200; and Mg at 0, 12, 24, 36, or 48 mg·L-1). The plants were irrigated starting with 100 mL fertilizer solution per day and increasing to 200 mL per day as plant growth progressed. The tomatoes were harvested at three stages of growth (five-leaf stage, flower initiation, and fruit initiation) for analysis of growth and composition. Samples of media for nutrient analysis were taken at each growth stage. Plant biomass increased linearly as fertilizer level increased or as time progressed. Generally, concentrations of nutrients in the medium increased linearly with increases in nutrients in the solutions. With time, N concentrations in media rose, but P, K, Ca, and Mg in the media fell. Concentrations of N, P, or K in leaves increased as nutrition increased, but Mg or Ca in leaves had no significant changes with increased nutrient supply. The N, P, Ca, and Mg in tissues fell, but K rose with time. Assessment of plant nutrition was best at flower initiation, with assessments at the other stages of development being judged as untimely or excessively variable. For optimum growth, critical concentrations of nutrients in the media (mg·kg-1) at flower initiation were judged to be 30 NO3-N, 30 P, 300 K, 2600 Ca, and 800 Mg and in leaves (g·kg-1) to be 35 N, 10 P, 70 K, 35 Ca, and 20 Mg. Optimum fertilization to reach these critical concentrations was reached with the third level (the regime with 100 mg N/L) or higher levels of nutrition.

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Uses of immature composts are difficult due to wide C:N ratio, high NH4 content, and phytotoxins, such as phenols and low molecular weight organic acids. This research focused on toxicity from high NH4 content. A compost of biosolids and wood chips was used. The compost was treated with (NH4)2SO4 to 2000 mg N·kg-1 (dry weight) to simulate an immature compost. The same compost without any external NH4 was used as a mature compost. Different proportions (regimes) of compost and soil provided 1/3, 1/6, and 1/12 compost (by volume). Each regime received potassium treatment at 0 or 0.6 g K·kg-1 as KC1. A nitrate treatment, at the same N rate as NH4 in immature compost, was factored into both mature and immature composts. For the mature compost, adding K generally decreased tomato (Lycopersicon esculentum Mill.) growth (measured by shoot mass) regardless of regimes. Adding Ca(NO3)2 to mature compost greatly increased plant growth for the regimes of 1/6 and 1/12. When the regime was 1/3, this increase diminished. For the immature compost, adding nitrate restricted plant growth due to excessive amount of N, including already high amounts of NH4. This response was especially true for the 1/3 regime. Adding K to immature compost greatly increased plant growth for the regimes of 1/3 and 1/6; K suppressed plant growth at the regime of 1/12. The results indicated that using K properly can effectively reduce immature compost toxicity due to high amount of ammonium. E-mail barker@pssci.umass.edu

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Glufosinate-ammonium is herbicidal through inhibition of glutamine synthetase in chloroplasts with the resulting accumulation of phytotoxic levels of unassimilated \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} . The herbicide is applied normally as a foliar spray at concentrations of 100 to 500 mg·L-1. Effect of root-applied herbicide on \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} accumulation was studied in hydroponics. Tomato seedlings (Lycopersicon esculentum Mill.) were grown in a nitrate-based solution (Hoagland no. 1) with herbicide added to active ingredient concentrations of 0, 6, 12, 25, and 50 mg·L-1. In another treatment, an ammonium-based solution was used to assess \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} accumulation from an external source. Harvest and analyses of plant tissue began with first symptoms of phytotoxicity from the herbicide and proceeded at 3-day intervals until plant death with the most extreme treatments. Free \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} was extracted by homogenation of fresh tissues in a 1-m KCl–0.02–m CuSO4 solution. Ammonium was determined by volumetric procedures. By 6 days after treatment, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} concentrations in tissues increased curvilinearly from nil to 1.5 mg N/g fresh tissue with increases in herbicide in the solution. Classic symptoms of ammonium toxicity were evident. The 50 mg·L-1 herbicide concentration was lethal at 6 days after treatment, and the 25 mg·L-1 concentration was lethal at 12 days when the experiment was terminated. Ammonium accumulation with the lower concentrations of herbicide or with externally supplied \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} was below phytotoxic levels at the end of the 12-day period. Amassment of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} in foliage followed distinctly different patterns with the herbicide or external supply. Accumulation with the herbicide was mainly in the foliage, whereas with the externally supplied \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} , accumulation in roots exceeded that in shoots with no evidence of phytotoxicity. Results indicate that root-applied glufosinate-ammonium is translocated to shoots where it initiates accumulation of phytotoxic \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} levels. E-mail barker@pssci.umass.edu

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Glufosinate-ammonium is herbicidal through inhibition of glutamine synthetase in chloroplasts with the resulting accumulation of phytotoxic levels of unassimilated NH 4 + . The herbicide is applied normally as a foliar spray at concentrations of 100 to 500 mg·L-1. Effect of root-applied herbicide on NH 4 + accumulation was studied in hydroponics. Tomato seedlings (Lycopersicon esculentum Mill.) were grown in a nitrate-based solution (Hoagland no. 1) with herbicide added to active ingredient concentrations of 0, 6, 12, 25, and 50 mg·L-1. In another treatment, an ammonium-based solution was used to assess NH 4 + accumulation from an external source. Harvest and analyses of plant tissue began with first symptoms of phytotoxicity from the herbicide and proceeded at 3-day intervals until plant death with the most extreme treatments. Free NH 4 + was extracted by homogenation of fresh tissues in a 1-m KCl–0.02–m CuSO4 solution. Ammonium was determined by volumetric procedures. By 6 days after treatment, NH 4 + concentrations in tissues increased curvilinearly from nil to 1.5 mg N/g fresh tissue with increases in herbicide in the solution. Classic symptoms of ammonium toxicity were evident. The 50 mg·L-1 herbicide concentration was lethal at 6 days after treatment, and the 25 mg·L-1 concentration was lethal at 12 days when the experiment was terminated. Ammonium accumulation with the lower concentrations of herbicide or with externally supplied NH 4 + was below phytotoxic levels at the end of the 12-day period. Amassment of NH 4 + in foliage followed distinctly different patterns with the herbicide or external supply. Accumulation with the herbicide was mainly in the foliage, whereas with the externally supplied NH 4 + , accumulation in roots exceeded that in shoots with no evidence of phytotoxicity. Results indicate that root-applied glufosinate-ammonium is translocated to shoots where it initiates accumulation of phytotoxic NH 4 + levels. E-mail barker@pssci.umass.edu

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