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  • Author or Editor: A. Milling x
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Abstract

Multiple applications of nitrapyrin (5 ppm/pot/week) increased NO3-N retention significantly over the control, and medium NO3-N was consistantly higher with multiple applications than with a single preplant application of nitrapyrin (50 ppm) when NO3-N was the fertilizer source. Multiple applications of nitrapyrin were less effective in increasing plant growth than a single application with an NH4-N fertilizer source.

Open Access
Authors: and

Responses of two hydroponically grown marigold species, Tagetes erects L. `pumpkin Crush' and T. patula L. `Janie Yellow', to Mn concentrations of 0.5 mg·liter-1 or 10 mg·liter-1 with KNO3 and Ca(NO3)2 (NO3 source) or NH4N O3 as the N source were investigated. In both species, Mn uptake was enhanced with the NO3 source while reduced with NH4NO3. With Mn supplied at 0.5 mg·liter-1 and NO3 as the N source, T. erects absorbed twice the Mn per gram of dry matter as T. patula. T. erecta accumulated higher concentration of Mn in the shoot than in the root irrespective of the N source. T. patula accumulated higher concentration of Mn in the roots with the NO3 source while NH4NO3 shifted the Mn accumulation to the shoot. Growth of both species was suppressed with 10 mg Mn/liter and the suppression was greater with the NO3 source than with the NH4NO3. These results indicate an interspecific response to Mn concentration as well as an N source influence on the uptake of Mn in marigold grown under hydroponic conditions.

Free access

Abstract

Suppression of denitrification with multiple, banded applications of nitrapyrin totaling 206 g/ha increased N percentage in plants and yield of field-grown sweet corn. Lower (41 g/ha) concentration of banded nitrapyrin and all broadcast applications of nitrapyrin did not increase N percentage or yield consistently.

Open Access

Pathogenic bacteria, such as Xanthomonas campestris pv. pruni, cause diseases of significant economical implications in the Prunus genus. Cecropins are naturally occurring bactericidal peptides found in the hemolymph of insects. Cecropins cause channel formation in membranes and lysis of bacterial cells. We are interested in engineering the gene for cecropin into peach (Prunus persica) and other fruit tree species. The objective of this study was to determine the effect of cecropin B on viability, using fluorescein diacetate staining, and on changes in transmembrane electrical potential (PD) using the fluorescing probe merocyanine-540. Protoplasts were isolated from shoot-tip cultures in a CPW13M (salts + 0.71M mannitol) solution containing 2% cellulase and 0.5% macerase, while cells were isolated in CPW15.4S (salts + 0.45M sucrose) containing 0.5% cellulase and 0.5% macerase. Cecropin B (1μM) had no effect on viability and changes in PD, while 10μM had a slight effect, and 100μM cecropin B caused significant depolarization and lysis of peach protoplasts. No effect on viability and change in PD were observed in cells when treated with 1-100μM cecropin B. These results suggest that cells and protoplasts of peach can resist cecropin B in the concentration range that causes lysis of plant pathogenic bacteria. The implication of using cecropin to increase microbial disease resistance will be discussed.

Free access

Crop-specific tailoring of fertilizer composition and timing of application reduces expense and runoff pollution. We examined the effects N forms and ratios have on growth, development, and utilization of nutrients in poinsettia (Euphorbia pulcherrima Willd. Ex Klotz.). Rooted cuttings of poinsettia `Freedom' were grown to flowering (10 weeks) in aerated solution culture under greenhouse conditions. Treatments consisted of five N ratios (percent ammonium: percent nitrate) of 100:0, 75:25, 50:50, 25:75, and 0:100 with a total N concentration of 150 mg·L–1. Dry mass for all plant parts and height increased as the ratio of NO 3 increased. Leaf and bract areas were greatest with ratios of 25:75 and 50:50, respectively. Plants receiving 100% NH 4 + exhibited severe ammonium toxicity symptoms and uptake of all macronutrients was suppressed. Average weekly uptake of NH 4 + , NO 3 , P, and K was significantly affected by the treatments. Maximum uptake of NO 3 and K occurred with 100% NO 3 , P with 25:75, and NH 4 + with 100% NH 4 + . Uptake averaged across all treatments was divided into physiological growth stages (GS) to identify peak demand periods. The greatest uptake of NH 4 + and NO 3 was from the beginning of treatments to floral induction (GSI). Uptake of P, K, and Mg peaked at GSII, floral induction to visible bud. Visible bud to anthesis (GSIII) had the lowest uptake for all nutrients. These results demonstrate how NH 4 + : NO 3 ratios and stage of development can influence growth and nutrient absorption.

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Authors: and

Abstract

Nitrapyrin at 50 ppm, increased dry weights of tomato (Lycopersicon esculentum Mill.) and total N when pine bark comprised part of the medium and NH4 was part of the N treatment. If the medium consisted only of pine bark, nitrapyrin increased dry weights and total plant N with NO3–N and/or NH4–N treatments. The NO3–N level in the medium was higher with all N treatments when nitrapyrin was incorporated. The increase in plant growth is directly related to the higher NO3–N levels in each medium where nitrapyrin was incorporated. The higher media NO3–N with nitrapyrin are attributed to inhibition of the nitrification process and a subsequent inhibitory effect on NO3–N loss.

Open Access

Abstract

The establishment of an average elemental composition for snap bean to satisfy nutritional labelling requirements is probably not possible. Analysis for the elemental content of 40 frozen snap bean samples collected at 8 locations in the United States revealed a wide range in concentration for the 18 elements determined. Several causes for this wide variation are suggested.

Open Access

Abstract

In a laboratory incubation study with soil inoculum, terrazole [5-ethoxy-3(trichloromethyl)1,2,4 thiadiazole] at 0.02 to 200 ppm in liquid culture suppressed N2 and N2O evolution and increased NO3-N retention. A Cecil clay soil, treated with terrazole at concentrations of 0.5 and 2.0 ppm, retained more NO3-N than the control in a greenhouse study.

Open Access

Abstract

Inhibition of N2 and N2O evolution from a liquid medium inoculated with soil was obtained with low levels (0.2, 2, and 20 ppm) of 2-chloro-6-(trichloromethyl)pyridine. Concurrent with the reductions in N2 and N2O evolution was increased NO3 retention in the medium. Results from this study confirm that nitrapyrin effectively inhibits denitrification in vitro at rates comparable to that applied in the field.

Open Access

Abstract

N-demand periods and the form and quantity of N absorbed during the growth cycle of sweet corn (Zea Mays L.) was determined for ‘Silver Queen’ grown in solution culture with a N ratio of 50% NO3–50% NH4. Absorption of NO3 and NH4 were similar up to the tasseling stage. During the tasseling stage, NO3 was absorbed at rates greater than NH4, while during the ear development stage NH4 was absorbed at rates higher than NO3. Evaluation of N demand during the growth cycle shows that 60% of the total N absorbed occurred during the tasseling-ear development stage. These results indicate that with ‘Silver Queen’, greater efficiency of applied N fertilizer can be obtained by correlating rate of N and form of N to a specific growth stage.

Open Access