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  • Author or Editor: Allen V. Barker x
  • Journal of the American Society for Horticultural Science x
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The herbicidal action of foliar applications of glufosinate-ammonium (GLA) is due to toxic accumulation of unassimilated NH4 + in leaves; however, the effects of root-applied GLA on NH4 + accumulation and plant growth are unknown. In a dose-response hydroponics experiment, tomato (Lycopersicon esculentum Mill.) plants were grown in nitrate-based solutions with GLA added at 0, 6, 12, 25, or 50 mg·L-1. To observe plant responses to an exogenous NH4 + source with herbicide-induced responses, plants were grown in an NH4 +-based solution without GLA addition. At 6 days after treatment (DAT), GLA in solution at 25 mg·L-1 produced partial leaf wilting, chlorosis, and necrosis of foliage, and at 50 mg·L-1, plants were fully wilted and necrotic. Ammonium (NH4 +-N) concentration in shoots at 6 DAT increased from 0 to 6 mg·g-1 fresh weight with increasing GLA in the nutrient solution. Ethylene evolution doubled (from 4 to 8 nL·g-1·h-1, fresh weight) with increases in GLA from 0 to 25 mg·L-1 but declined with apparent plant death with GLA at 50 mg·L-1. Other treatments, including NH4 + nutrition, did not induce toxicity symptoms in leaves or give increases in NH4 + accumulation or ethylene evolution during the 6 days of the experiment. In a time-course experiment, tomato plants treated with GLA at 25 mg·L-1 were chlorotic at 4 DAT. Ethylene evolution (fresh weight basis) rose from an initial rate of 2.6 nL·g-1·h-1 to 8.3 nL·g-1·h-1 after 4 days. At 9 DAT, all plants receiving this treatment died. In the time-course experiment, an exogenous NH4 + treatment caused a slight inhibition in shoot fresh weight relative to NO3 - nutrition with no GLA but caused no visible symptoms and only slight enhancements in NH4 + accumulation and ethylene evolution over the 9-day period. Following GLA treatment, NH4 + accumulated in the shoots and increased sharply with time, whereas exogenous NH4 + led to NH4 + accumulation primarily in roots. Results suggest that GLA was absorbed by roots and translocated to shoots, where it initiated accumulation of NH4 + and ethylene evolution as indications of herbicidal action. Chemical name used: glufosinate-ammonium, GLA.

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Studies of ethylene evolution by tomato (Lycopersicon esculentum Mill.) fruit were conducted with plants receiving NH4-N or NO3-N nutrition. Fruit of plants grown with NH4-N had a higher occurrence of blossom-end rot (BER), higher NH4-N concentrations, and higher ethylene evolution rates than fruit from plants grown with NO3-N. Fruit of plants grown with NO3-N showed no enhancement in ethylene evolution with BER development. Fertilizing these plants with Ca(NO3)2 doubled the average Ca concentration of fruit and restricted BER development. Ammonium suppressed Ca accumulation in fruit relative to those grown with NO3-N. Ethylene evolution increased as fruit from plants receiving NO3-N ripened, but without a concomitant increase in NH4-N concentrations in the fruit. Ammonium accumulation in fruit induced BER and enhanced ethylene evolution. These relationships were unique, for NH4-N accumulation did not seem to be a naturally occurring phenomenon in ripening fruit or in fruit that have BER arising from other causal factors.

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Abstract

Bean, sweet corn, cucumber and pea plants were susceptible to ammonium toxicity when cultured on an ammonium source of N. Growth of plants was normal, however, when the pH of the nutrient solution was maintained near neutrality by the addition of CaCO3. The control of acidity was effective in altering the distribution of ammonium; ammonium accumulation in the shoot was lessened and accumulation of amides in roots was enhanced. A natural resistance to ammonium was exhibited by the onion plant since it did not accumulate ammonium in the leaves; however, the nonchlorophyllous bulb acted as an ammonium sink.

Open 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

Abstract

Studies of plant micronutrient uptake and translocation have indicated that excess Zn induces leaf chlorosis associated with Fe deficiency. Leaves from Spinacia oleracea L. and Lycoperiscon esculentum Mill, grown with Hoag-land's No. 1 and minor element nutrient solutions minus Fe or with additional Zn (0.17 mm) exhibited symptoms of Fe deficiency as interveinal chlorotic bleaching for spinach and interveinal chlorotic mottling for tomato. Similarly, the ultrastructure of spinach and tomato leaf chloroplasts from plants grown with additional Zn corresponded to the altered structural integrity representative of Fe-deficient chloroplasts for each plant species. Supplemental Fe (0.19 mm) added to the nutrient supply alleviated the effects of excess Zn as illustrated by a dark green leaf and an enhanced grana-fretwork system of mesophyll chloroplasts of spinach and tomato. These results constitute morphological evidence of Zn-induced Fe deficiency.

Open Access

This research evaluated production of wildflower sods in soil and composts of mixed municipal solid waste, biosolids and woodchips, fall leaves, and mixed agricultural wastes. Soil or composts were laid on plastic sheeting in outdoor plots, and a mixture of wildflower seeds was sown in July and in September in separate experiments. Quality of sods was assessed in two growing seasons. Best sods with respect to seed germination, stand establishment, and intensity and diversity of bloom over two seasons occurred in mature biosolids compost and in agricultural waste compost. These composts were low in ammonium but rich in total N. Germination and growth of wildflowers were limited by high ammonium concentrations in immature biosolids composts. Nitrogen deficiency limited sod growth and quality in leaf composts. Poor N nutrition and weed competition restricted sod production in soil. Fertilization of soil promoted unacceptably large weed growth. Summer seeding or fall seeding resulted in good sods, but many annual flowers that appeared in the summer seeding were absent in the fall-seeded planting. Using plastic-lined plots was a convenient system for evaluating composts and other media in outdoor culture.

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Abstract

Nitrapyrin, etridiazol, fenaminosulf, sodium azide, and a formulated product of aromatic substances and alkenes were evaluated as nitrification inhibitors under greenhouse conditions for radish (Raphanus sativus L. ‘Cherry Belle’) fertilized with sewage sludge. Nitrapyrin and etridiazol inhibited nitrification, but their use restricted plant growth and lowered the Ca and Mg concentrations of the plants. Nitrification was inhibited slightly by fenaminosulf, which had little effect on plant growth and composition. Sodium azide and the formulated product were not effective as nitrification inhibitors. The azide was phytotoxic, but the formulated product had no toxic effects on growth. The toxic effects of chemicals with efficacy as nitrification inhibitors were due largely to the accumulation of NH4-N in the medium. Chemical names used: 2-chloro-6-(trichloromethyI)pyridine (nitrapyrin); 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole (etridiazol); and sodium p-(dimethylamino)benzenediazosulfonate (fenaminosulf).

Open Access

Abstract

Spinach, Spinacia oleracea, L., cv. America, Heavy Pack, and Hybrid 424 were grown in sand culture with variable NO3 concentrations from 0.187 to 48 meq/l. The cultivars were representative of savoyed, semisavoyed, and smooth-leaf types, respectively. The plants were harvested when those cultured at 12 and 18 meq NO3/l had obtained approximate market maturity. At this time an array of deficiency, sufficiency, and toxicity symptoms were evident. Great differences in NO3 accumulation and critical NO3 concentrations occurred among cultivars. Critical NO3-N concentrations for the whole leaves of spinach plants were: ‘America’, 0.17%, ‘Heavy Pack’, 0.15%, and ‘Hybrid 424’, 0.045% of their dry weights. Calculations relating spinach consumption and impaired human health suggest that adult health should not be affected even with massive ingestion of spinach.

Open Access

Abstract

Brussels sprouts (Brassica oleracea var. gemmifera, Zenker) were grown in sand culture at variable Ca levels in the greenhouse. More Ca accumulated in leaves than in sprouts. With plant growth restricted by late seeding and low greenhouse temp, typical Ca deficiency symptoms occurred on the growing points of plants cultured at low Ca levels, but internal browning did not occur. When growth was enhanced by cultural modifications, sprout internal browning occurred at low Ca levels and decreased as Ca levels were increased. The incidence of internal browning was related to low Ca concn in sprouts.

Open Access

Abstract

The accumulation of cations and NO3-N was higher in cucumber shoots than in pea shoots grown on nitrate nutrition. Total N concn in shoots did not differ between the species. Ammonium nutrition suppressed cation accumulation in cucumbers but not in peas. Differences in cation accumulation in the shoots are attributed to the form in which N is translocated from root to shoot.

Open Access