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  • Author or Editor: Kenneth A. Corey 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.

Open Access

A method was developed to improve the yield and quality of chicons of witloof chicory (Cichorium intybus L.) forced hydroponically from roots taken following long-term storage. The method combines the use of a resilient material (polyurethane foam) with the application of pressure to the developing chicons. At the start of forcing, weights of 0, 150, 300, 450, and 900 g/root were applied to the crown and maintained until harvest. Marketable yields and density of chicons of the late-forcing cultivar Faro increased with increasing weight applied. Increasing weight also significantly decreased the length: diameter ratio of chicons, an indicator of quality. Increased marketable yield and improved quality of `Bea' (intermediate to late-forcing cultivar) chicons were achieved with application of 450 g/root. The technique provides a tool for improving economic yields of late-season, hydroponically forced witloof chicory.

Free access

Urea fertilization of `Heinz 1350' tomato (Lycopersicon esculentum Mill.) in sand or soil culture did not enhance ethylene evolution or restrict growth relative to plants receiving \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathbf{NO}_{\mathbf{3}}^{\mathbf{-}}\) \end{document} whereas \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathbf{NO}_{\mathbf{4}}^{\mathbf{+}}\) \end{document} nutrition doubled the relative rates of ethylene evolution and restricted relative growth. Inhibitors of N transformations in media (nitrapyrin, Np; hydroquinone, HQ; and phenylphosphorodiamidate, PPD) had no apparent stimulator effects on ethylene evolution of plants grown on urea or \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathbf{NO}_{\mathbf{3}}^{\mathbf{-}}\) \end{document} nutrition in sand or soil. Ethylene evolution was enhanced by PPD relative to that by Np or HQ for plants receiving \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathbf{NO}_{\mathbf{4}}^{\mathbf{+}}\) \end{document} nutrition. Each inhibitor had toxic effects on plant growth. Increasing K+ supply from 0 to 8 mm in nutrient solutions decreased ethylene evolution and increased plant growth with urea fertilization. Urea had low phytotoxicity if its hydrolysis to \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathbf{NO}_{\mathbf{4}}^{\mathbf{+}}\) \end{document} was prevented in the media. Chemical names used: p-dihydroxybenzene (hydroquinone); benzenephosphorodiamide (phenylphosphorodiamidate); 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin).

Free access

Procedures for predicting optimum packaging conditions of modified atmosphere packages (MAP) of tomato (`Heinz 1370') were developed. The relationship between O2 consumption rate and O2 concn (RRo2) was determined using O2 depletion data collected by enclosing tomatoes in jars and sampling head space O2 concn over time. The fitted function was then used in conjunction with other input variables: (1) film permeability to O2 (PO2), (2) film surface area (A), and (3) fruit weight in packages (Wp) to develop the final predictive equation based on Fick's law of gas diffusion. Predictive power of the equation was tested by comparing the steady state O2 concn achieved experimentally with those predicted for a wide range of packaging conditions. Packaging conditions included film surface area, weight of fruit in packages, and O2 permeability of the film (0.0426 and 0.0620 ml/kg hr). Prediction curves showing steady state O2 concn vs. packaging ratio (A/Wp) closely resembled the best fit curves of data. The effect of temperature on steady state O2 concn in MA bags was also examined. Increasing temperature from 20°C to 28±2°C had little effect but decreasing temperature to 10°C led to higher in-package O2 concn. Results indicate that predictive equations can be used to select appropriate films and optimize packaging ratios to achieve desired steady state O2 concn for MAP of tomatoes.

Free access

A rapid steady state method for measurement of gas permeability of polymeric films was developed. Films were sealed between two equal volume chambers with pure O2 and pure N2 flowing through opposite sides. Oxygen concentration in the N2 cell was measured over time until steady state was reached. The method was used to determine oxygen permeability of two different films. Results from four replications on each film indicated excellent repeatability with coefficients of variation less than 3%. The time required to reach steady state oxygen concentration was dependent upon film type, flow rate, and temperature. The higher the N2 flow rate the shorter the time to reach steady state O2 concentrations. The slowest measurement at the lowest flow rate of 27 ml/min took less than 3 hours to collect the data necessary to achieve steady state. Increasing temperature from 10°C to 20°C resulted in an approximately 40% increase in O2 permeability for both films tested. The technique will be a valuable tool for measuring permeabilities of new films and the same film at different temperatures, and for selecting the appropriate material for modified atmosphere packaging of fresh produce.

Free access

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.

Free access

Diurnal changes in air and soil temperatures lead to temperature gradients between air and soil, between roots and shoots, and within plant organs. In response to these gradients, fluctuations in gas pressures may develop in organs that are resistant to exchange of gases. These fluctuations may regulate mass flow of gases or solutions within plants. Patterns of diurnal temperature changes were generated to illustrate temperature gradients between roots and shoots. Experimental confirmation of pressure changes induced by temperature differences between roots and shoots were measured with water manometers attached to stumps of detopped tomato plants. When roots were maintained 8 C lower than shoots, internal pressure decreased by 22 cm H2O. Reversing the direction of the temperature gradient led to an approximately equal and opposite pressure change and to sap movement. These results support a hypothesis that internal pressure gradients resulting from temperature gradients contribute to transport of substances in plants.

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It frequently takes days to weeks for testing films to determine if desired steady state concn of gases are reached when atmospheres are passively modified through commodity respiration. Our objective was to develop a rapid method to test the appropriateness of packaging films and designs using active modification of the atmosphere. Repeated exposures of commodities to partial vacuum were followed by infusion of N2 to 1 atm. Three to five minutes were allowed following each N2 infusion. Initial O2 concn achieved in packages (polyethyl vinyl acetate) depended upon the extent of the vacuum and the number of exposures. Within packages of tomatoes, O2 concn of 8.3 ± 0.5% and 5.0 ± 1.0% were measured following exposure to 460 and 360 mm Hg vacuum, respectively. Three exposures of cabbage and muskmelon packages to 460 mm Hg resulted in O2 concn of 5.1 ± 1.4% and 5.0 ± 1.4%, respectively. Maintenance or deviation from actively established atmospheres was determined within hours.

Free access

Water manometers were connected to fruits of tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.), and then fruits were submerged in water baths providing initial temperature gradients between fruit and water of 0 to 19C. Apple (Malus domestics Borkh.) fruits, carrot (Daucus carota L.) roots, witloof chicory (Cichorium intybus L.) roots, rhubarb Rheum rhabarbarum L.) petioles, and pokeweed (Phytolacca americana L.) stems were subjected to water bath temperature gradients of 5C. Internal partial vacuums developed in all organs within minutes of imposing the gradients. The maximum partial vacuums in tomato and pepper fruits increased with increasing temperature gradients. Uptake of water accompanied changes in internal pressure reaching maxima of 17% (w/w) and 2% (w/w) of pepper and tomato fruits, respectively, after 22 hours. Maximum pressure changes achieved in bulky organs deviated from those predicted by the ideal gas law, possibly due to concomitant changes in gas pressure upon replacement of intercellular spaces with water and dissolution of CO2. Partial vacuums also developed in pepper fruits, rhubarb petioles, and pokeweed stems following exposure to air 15C cooler than initial organ temperatures. Results point to the role of temperature gradients in the transport of liquids and gases in plant organs.

Free access

Abstract

Tomato plants (Lycopersicon esculentum Mill. ‘Heinz 1350’, yellow-green-5, and neglecta-1) were grown in sand culture with 15 mm NH 4 + or NO 3 and with K+ varying from 0 to 8 mm. Other nutrients were provided at the concentrations of Hoagland's solution. The medium supplying NH 4 + was buffered with CaCO3 (pH 6.9) or was unbuffered (pH 3.4). Silver ions (0.01 μm) were incorporated in the nutrient solution in one experiment. Ammonium nutrition relative to NO 3 nutrition elevated rates of ethylene evolution from all genotypes, but yg-5 and neg-1 showed resistance to NH 4 + toxicity and exhibited relatively low ethylene evolution. Ethylene evolution declined as K+ supply increased. Accelerated rates of ethylene evolution did not occur at tissue K+ concentrations >10 g·kg−1 of the dry weights of shoots with NO 3 nutrition, but higher K+ levels were required with NH 4 + nutrition. Putrescine concentrations in leaves of ‘Heinz 1350’ supplied with NH 4 + were 2 to 5 times greater than in leaves of plants supplied with NO 3 . Potassium deficiency increased putrescine accumulation regardless of N form. Spermidine concentrations in leaves of plants supplied with NH 4 + were lower than in those supplied with NO 3 , whereas spermine concentrations were unaffected by treatments. ‘Heinz 1350’ grown in NH 4 + -based nutrient solutions with 0.01 μΜ Ag+ had low rates of ethylene evolution and developed few symptoms of NH 4 + toxicity. Quantities of ethylene and putrescine produced by tomato genotypes susceptible to the nutritional stresses were linked directly to the degree of stress imposed, and symptoms of NH 4 + toxicity were related to increased ethylene synthesis.

Open Access