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  • Author or Editor: Allen V. Barker x
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Abstract

Three genotypes (‘Heinz 1350’, neglecta-1, yellow-green-5) of tomato (Lycopersicon esculentum Mill.) were grown during winter under natural light or with natural light supplemented with light from high-pressure sodium vapor (HPS) lamps (200-400 μmol·s-1·m-2). The plants were grown in sand culture with NO- 3 or NH+ 4 nutrition. Symptoms resembling Ca, Mg, K, and P deficiencies developed on the foliage of plants exposed to radiation from HPS lamps. Clustering of short branches in the lateral and terminal growing regions (yg-5) and epinasty (‘Heinz 1350’ and neg-1) developed on the shoots receiving HPS irradiation. Ethylene evolution by the three genotypes was enhanced by the supplemental lighting and NH+ 4 nutrition. Concentrations of Ca, Mg, K, and P in the shoots were lower in plants receiving HPS irradiation than in plants grown under natural light. Dry weights of shoots were increased by supplemental lighting relative to the weights of the plants receiving only natural light. Total accumulation of Ca, Mg, K, and P was not suppressed by HPS lighting, indicating that the phytotoxic effects of the lamps was not due to their effects on total nutrient accumulation.

Open Access

Several factors inducing physiological stress in plants were investigated for their effects on foliar ammonium accumulation and ethylene evolution in tomato (Lycopersicon esculentum Mill.). Plants grown on ammonium nutrition (0.015M NH4 +) in solution culture had elevated rates of ammonium accumulation and ethylene evolution relative to plants grown on nitrate nutrition at the same molar concentration. Inhibitors of ethylene action (0.001 mM Ag+) or synthesis (0.01 mM amino-oxyacetic acid) restricted ammonium accumulation and ethylene evolution relative to rates by untreated controls receiving ammonium nutrition. The inhibitors lessened the expression of ammonium toxicity. Stress from salinity, drought, or flooding in soil increased ammonium accumulation and ethylene evolution. Plants infected with root-knot nematode had variable rates of ethylene evolution in response to variations in ammonium accumulation. Ammonium accumulation and ethylene evolution appear to be factors in the expression of physiological stress.

Free access

Calcium-rich vegetables in the diet could ameliorate the potential for calcium (Ca) deficiency in human nutrition. This study investigated the prospect of increasing Ca density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management in a greenhouse. Eighteen lettuce cultivars including butterhead, romaine, and loose-leaf phenotypes of heritage and modern genetics were tested. Organic fertilizer (3N–0.7P–3.3K) and commercial conventional fertilizer (20N–4.4P–16.6K) factored with three Ca levels (50, 100, 200 mg·L−1 as CaCl2) were the fertilizer regimes. Calcium in whole shoots was analyzed by atomic absorption spectrometry of oven-ashed samples. Heritage cultivars had a significantly higher Ca concentration (1.93% dry weight) than modern cultivars (1.54%). Loose-leaf phenotypes had the highest Ca concentration (2.06%) followed by butterhead (1.66%) and romaine (1.49%). Accumulation of Ca was higher with the conventional fertilizer (1.90%) than with the organic fertilizer (1.58%). Elevated Ca level in the fertility regimes raised the Ca concentration in lettuce from 1.56% at 50 mg·L–1 to a mean of 1.82% at 100 mg·L−1 and 200 mg·L−1. Large differences in Ca concentration occurred among individual cultivars with ranges from 1.27% to 3.05%. ‘Salad Bowl’, ‘Red Deer Tongue’, ‘Buttercrunch’, and ‘Bronze Mignonette’ were the top in cultivar ranking with mean Ca concentration of 2.50%, whereas ‘Adriana’, ‘Australe’, ‘Coastal Star’, and ‘Forellenschluss’ were low accumulators with a mean of 1.33%. Head size of cultivars had no correlation with Ca concentration. This experiment indicates that selection of nutrient regimes and cultivars can be used to increase Ca accumulation in lettuce.

Free access

Experiments were conducted to evaluate organic fertilizers in production of greenhouse-grown calibrachoa (Calibrachoa ×hybrida Llave & Lex) and marigold (Tagetes erecta L.) and nitrogen (N) leaching from containers during production. Calibrachoa was grown with five fertilizer treatments: one chemical, one organic-based, and three organic (liquid fish, oilseed extract, and a combination of oilseed extract and liquid fish). Marigold was grown with seven fertilizer treatments: one chemical and three organic (liquid fish, oilseed extract, and alfalfa pellets) used either alone or in combination. Chemical or organic-based fertilizers produced the best quality calibrachoa based on plant appearance and size. Liquid fish fertilizer produced healthy plants but smaller plants than those grown with chemical or organic-based fertilizers. Plants grown with oilseed extract were stunted and showed chlorosis. If oilseed extract was combined with liquid fish, the plants were similar to those grown with the chemical or organic-based fertilizers in size and quality. Chemical or liquid fish fertilizers produced the highest quality marigold based on plant appearance. Plants fertilized with alfalfa pellets were sparse and pale green. Oilseed extract produced the poorest growth and quality. If oilseed extract was combined with liquid fish or alfalfa, marigold plants were close in size and development to chemical-fertilized plants without nutrient deficiency and with some enhancement of nutrient levels in the leaves. The combination of alfalfa and liquid fish produced similar results. The highest N leaching resulted from plants fertilized by liquid fish, mostly in the form of ammonium nitrogen (NH4-N). Combining liquid fish with alfalfa or oilseed extract reduced the amount of N leached from the pots. The results suggest that organic fertilizers can be used successfully to grow commercial greenhouse crops but should be combined for good plant quality and environmental sustainability.

Free access

Abstract

The total number and length of new shoots of Leucothoe catesbaei Gray were significantly greater, and the plants were of better quality with NO3 nutrition than with NH4 or urea nutrition. Especially with the NH4-N sources, growth was as good as or significantly greater at pH 6 to 7 than at 4 to 5. The total number and length of new shoots of Rhododendron catawbiense Michx. cv. Roseum Elegans were not significantly affected by the N source or pH, although plant appearance was significantly better with NO3 nutrition than with NH4 or urea nutrition. The nitrification inhibitor, a substituted pyridine, had no significant effect on the growth and development of either leucothoe or rhododendron.

Open Access

Abstract

Consumption of spinach (Spinacia oleracea L.) with high NO3-N contents may be a health hazard to infants. Spinach leaves accumulate NO3-N when the plants are grown in a soil with high NO3-N availability. Experiments designed to evaluate the influence of nitrapyrin, a nitrification suppressor (2-chloro-6-(trichloromethyl)pyridine), on NO3-N concentrations in ‘America’ spinach and to develop a means of fertilization for maximum growth and minimum NO3-N levels in spinach were conducted. Nitrate accumulation in whole leaves and leaf fresh weights were lower with (NH4)2SO4 fertilization than with KNO3 fertilization. Nitrapyrin caused a further depression of NO3-N concentrations and plant growth with (NH4)2SO4 but had no effect on NO3-N accumulation and little effect on yield of plants fertilized with KNO3. The lesser growth with (NH4)2SO4 was apparently due to NH4-N toxicity. When half of the N was supplied as NH4-N and half as NO3-N, growth was equivalent to that of plants receiving only NO3-N, and NO3-N accumulation in the leaves was reduced by 35% without nitrapyrin and by over 50% with nitrapyrin. With this fertilizer combination, no toxicity to plant growth resulted from nitrapyrin applied at its recommended rate.

Open Access

Abstract

‘America’ spinach (Spinacia oleracea L.) is a savoy-leafed cultivar and tends to accumulate NO 3 ¯ in its leaf blades, petioles, and roots when the level of NO3-N nutrition is relatively high. ‘Hybrid 424’ spinach is smooth-leafed, larger in size, and accumulates much less NO 3 ¯ than ‘America’ especially when NO3-N nutrition is high. A greater NO 3 ¯ reductase activity in Hybrid 424, especially in its leaf blades, may account for its lower NO 3 ¯ content compared to that of ‘America’.

Open Access

Abstract

Cucumber (Cucumis sativus L.) plants accumulate more NO 3 ¯ than pea (Pisum sativum L.) plants. The differences in accumulation appear to be due to differences in the abilities of the two species to reduce NO 3 ¯ in their roots. Only 2% of the NO 3 ¯ reductase activity of cucumber was found in its roots, whereas nearly 92% of the activity was found in the blades. In pea, NO 3 ¯ reductase activity was more evenly distributed throughout the plant;67% of the activity was in the blades, 18% in the roots, and the remainder in the stems and petioles. Nitrate-N comprised 80% of the N present in bleeding sap of roots of cucumber plants from which the shoots had been excised. In contrast, NO3-N constituted only 30% of the N in the sap from pea roots, the remaining 70% of the N consisting of amino acids and amides. Asparagine or aspartic acid was the major carrier of reduced N in pea, and glutamine was the major carrier in cucumber. The differences in N transport and assimilation appear to bear considerably on plant composition and efficiency of N usage.

Open Access

Abstract

Tomato, tobacco, pepper, petunia, and eggplant were screened for their tolerance to continuous (NH4)2SO4 applications. Stem lesions, analogous to those which appear on tomato during ammonium toxicity, were formed on eggplant but not on the other species. Of the plants tested, tobacco was the most tolerant to applications of (NH4)2SO4. Potassium applications increased the ammonium concentration of tobacco tissues but lowered the ammonium concentration of tomato tissues. Diamine concentrations were increased by the application of (NH4)2SO4. The application of KCl decreased the putrescine concentration of tobacco and increased the concentration of cadaverine in tomato and tobacco. The application of putrescine-2HC1 in aqueous solution to cut stem ends of axillary shoots of tomato and tobacco induced the formation of stem lesions analogous to those formed by the (NH4)2SO4 fertilization of tomato. It is postulated that the tolerance of tobacco to stem lesion formation is related to putrescine utilization in nicotine synthesis.

Open Access

Abstract

Eighteen spinach cultivars were found to vary considerably in NO3 concentrations in their leaves. Smooth-leafed cultivars were lower in NO3 concentration than heavily savoyed cultivars. Some medium or semisavoyed cultivars were low NO3 accumulators, and others were high accumulators. A low degree of savoyedness appears to be a useful factor in the selection of spinach cultivars with tendencies for low NO3 accumulation.

Open Access