Utilization of Ammonium as a Nitrogen Source

Abstract

Dry matter accumulation of plants utilizing NH4F as the sole nitrogen source generally is less than that of plants receiving N03-unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH4' by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH4' as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 ± 0.1 by automatic additions of 0.01 N H2SO4 or Ca(OH)2. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH4' uptake per gram root dry weight were calculated from these data. Net CO2 exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO2 exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH4' per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO2 exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH4', which were initially about 50% lower at pH 4.1 than at 6.1, continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.Several plant species supplied with moderate concentrations of NH4, as the sole nitrogen source generally do not grow as well as when supplied with similar amounts of NO3- (7,8, 20 Increased acidity of the root-zone apparently initiates a series of events which result in increased degradation of organic nitrogen compounds stored within the leaves with release of free NH4+ or ammonia (2, 5). Availability of carbohydrate regulates reincorporation of the released NH4+ or ammonia into organic compounds and thus governs the occurrence of toxic effects (5), including reduced photosynthetic activity (1, 18). Based on this analysis of the literature, we propose that the reduction in plant growth associated with NH4' nutrition begins with the reduction in both root mass and uptake rate of NH4' per unit root mass in response to acidification of the root-zone during absorption of NH4+. The initial consequences of NH4' uptake on plant growth thus would be related to a restriction in nitrogen availability, including a reduction in leaf initiation and expansion ...

Agriculture for Space: People and Places Paving the Way

“…2). CELSS crop testing included wheat (Bugbee and Salisbury, 1988;Bugbee and Monje, 1992), soybean (Tolley-Henry and Raper, 1986), lettuce (Knight and Mitchell, 1988;Barta and Tibbitts, 1991), potato (Wheeler and Tibbitts, 1986;Wheeler et al, 1991a;Cao and Tibbitts, 1994), sweetpotato (Mortley et al, 1991, Bonsi et al, 1992, rice (Bugbee et al, 1994;Goldman and Mitchell, 1999), cowpea (Ohler and Mitchell, 1996), peanut (Mackowiak et al, 1998;Mortley et al, 2000), tomato (McAvoy et al, 1989;Gianfagna et al, 1998), and various alliums (Jasoni et al, 2004). Experiments were typically carried out in growth chambers with electric lighting, using either hydroponics or solid growing media in pots.…”

Wheeler Raymond Agriculture for Space: People and Countries Paving the Way

“…CELSS crop testing included wheat (Bugbee and Salisbury, 1988;Bugbee and Monje, 1992) [26,27], soybean (Tolley-Henry and Raper, 1986) [183], lettuce (Knight and Mitchell, 1988;Barta and Tibbitts, 1991) [99, 10], potato Cao and Tibbitts, 1994) [191,193,35], sweet potato , Bonsi et al, 1994, rice (Bugbee et al, 1994;Goldman and Mitchell, 1999) [28,67], cowpea [139], peanut [115,132], tomato [121,59], and various alliums (Jasoni et al, 2004) [86]. Experiments were typically carried out in growth chambers with electric lighting, using either hydroponics or solid growing media in pots.…”

Répercussions d'une alimentation azotée ammoniacale sur le métabolisme carboné photosynthétique chez le soja (Glycine max L Merr)

“…La fermeture des stomates en relation avec la nutrition azotée n'avait surtout été signalée jusqu'ici que dans des situations de carence, à la fois chez le soja (Grima-Pettenati et al, 1986) et chez d'autres végétaux tels que le tournesol (Goldbach et al, 1975) et le cotonnier (Radin et (Kpodar et al, 1978), le blé (Walker et al, 1984) et le haricot (Chaillou et al, 1986 (Grima-Pettenati, 1985). Selon Tolley-Henry et Raper (1986) …”