CONTENTS INTRODUCTION 483 METHODS FOR MEASURING NITROGENASE ACTIVITY IN LEGUME NODULES... 484 The Acetylene Reduction Assay (ARA) 485 Measurement of Nodule H2 Evolution . .... 487 Measured Values Nitrogenase Activity: Past and Present 489 VIVO ACTIVITY: POTENTIAL AND LIMITATIONS 490 Inhibition N2 Fixation 02 Limitation Activity 492 ENVIRONMENTAL FACTORS AFFECTING ACTIVITy 498 Restriction Phloem Sap Supply Nitrate Fertilization 500 Drought Stress 502 DEVELOPMENTAL LONG-TERM ADAPTA nON TO...

Partitioning and utilization of assimilated C N were compared in nonnodulated, NO(3)-fed nodulated, N(2)-fed plants white lupin (Lupinus albus L.). The NO(3) regime used (5 millimolar NO(3)) promoted closely similar rates growth assimilation as the symbiotic plants. Over 90% absorbed by was judged to be reduced roots. Empirically based models flow demonstrated that patterns incorporation into dry matter exchange among plant parts essentially two forms nutrition. transported types proportions...

An empirical modeling technique was developed for depicting quantitatively the transport and partitioning of photosynthetically fixed C symbiotically N during 10-day intervals a 40-day period in growth nodulated plants white lupin (Lupinus albus L. cv. Ultra). Model construction utilized data consumption plant parts C:N weight ratios xylem phloem fluids serving specific organs. Formulas were derived from calculating net between phloem. The models provided quantitative information on...

This study evaluated the efficacy of using a combined biofilm-biochar approach to remove organic (naphthenic acids (NAs)) and inorganic (metals) contaminants from process water (OSPW) generated by Canada's oil sands mining operations. A microbial community sourced an OSPW sample was cultured as biofilms on several carbonaceous materials. Two biochar samples, softwood bark (SB) Aspen wood (N3), facilitated most growth (measured protein assays) were used for NA removal studies performed with...

The transition to net-zero emission energy systems creates synergistic opportunities across sectors. For example, fuel hydrogen production from water electrolysis generates by-product oxygen that could be used reduce the cost of carbon capture and storage (CCS) essential in decarbonization clinker cement making. To assess this opportunity, a techno-economic assessment was carried out for using oxy-combustion natural gas-fueled plant coupled CCS. Material flows were assessed reference case...

Empirically based models depicting exchanges of C, N, and H(2)O in phloem xylem among organs nodulated white lupin (Lupinus albus cv Ultra) were constructed for the interval 51 to 58 days after sowing. Information was incorporated on economy plant parts, solute composition transport fluids collected at selected sites plant, photosynthetic inputs, transpirational losses, translocatory activities different age groups leaflets stem + petiole segments shoot. Partitioning C N showed preferential...

The aim of the present study was to test hypothesis that N content or composition phloem sap supplies nodulated roots may play a role in feedback regulation nitrogenase activity by increasing nodule resistance O2 diffusion. Treating shoots lupin (Lupinus albus cv Manitoba) soybean (Glycine max L. Merr. Maple Arrow) with 100 [mu]L L-1 NH3 caused 1.3-fold (lupin) and 2.6-fold (soybean) increase total without altering its C content. due primarily 4.8-fold 10.5-fold concentration glutamine N. In...

The effects of increasing rhizosphere pO 2 on nitrogenase activity and nodule resistance to O diffusion were investigated in soybean plants [ Glycine max (L.) Merr. cv. Harosoy 63] which (EC 1.7.99.2) activities inhibited by (a) removal the phloem tissue at base stem (stem girdling), (b) exposure roots 10 m M NO 3 over 5 days (NO ‐treated), or (c) partial inactivation an nodulated 100 kPa (O ‐inhibitcd). In control had been treated with , concentrations increments from 20 70 did not alter...

In many legumes, the nitrogen fixing root nodules produce H2 gas that diffuses into soil. It has been demonstrated such exposure of soil to can promote plant growth. To assess whether this may be due H2-oxidizing microorganisms, bacteria were isolated from treated with under laboratory conditions and soils collected adjacent producing soybean nodules. Nineteen isolates obtained all exhibited a half-saturation coefficient (Ks) for about 1 ml l(-1). The identified as Variovorax paradoxus,...

When arrival of shoot supplied carbohydrate to the nodulated root system soybean was interrupted by stem girdling, chilling, or leaf removal, nodule pools were utilized, and a marked decline in rates CO2 H2 evolution observed within approximately 30 minutes treatment. Nodule excision studies demonstrated that respiration associated with rather than metabolism, since 3.5 hours treatment, nodules respired at less 10% initial rates. Apparently, continuous supply from is required support nodule,...

An open gas exchange system was used to monitor the nonsteady state and steady changes in nitrogenase activity (H(2) evolution N(2):O(2) Ar:O(2)) respiration (CO(2) evolution) attached, excised, sliced nodules of soybean (Glycine max L. Merr.) exposed external pO(2) 5 100%. In attached nodules, increases steps 10 or 20% resulted sharp declines rates H(2) CO(2) evolution. Recovery these values equal greater than their initial occurred within 60 minutes exposure higher pO(2). more rapid at...

The economy of C use by root nodules was examined in two symbioses, Vigna unguiculata (L.) Walp. (cv. Caloona):Rhizobium CB756 and Lupinus albus L. Ultra):Rhizobium WU425 over a 2-week period early vegetative growth. Plants were grown minus N water culture with cuvettes attached to the nodulated zone their primary roots for collection evolved CO2 H2. Increments total plant nodules, C:N weight ratios xylem phloem exudates studied periodic sampling from populations. Itemized budgets...

ABSTRACT Hydrogen gas (H 2 ) is an obligate byproduct of the N ‐fixing enzyme, nitrogenase, claiming about 5–6% crops’ net photosynthesis but most, if not all H lost from nodules oxidized by soil surrounding root system plant. When soils recently used to support growth legumes were exposed at a rate and duration similar that adjacent legume nodules, fertility was enhanced in comparison with treated air. Under growth‐chamber field conditions, ‐treated improved performance spring wheat,...

A novel, pulse-modulated spectroscopic system for measuring fractional leghemoglobin oxygenation and infected cell O(2) concentration (O(i)) in intact attached nodules of soybean (Glycine max) is described. The noninvasive uses a pulsed (1000 Hertz) light-emitting diode coupled to an optical fiber illuminate the nodule with light at 660 nanometer. second receives portion reflected from directs this photodiode. lock-in amplifier measures only signal photodiode which phase diode, voltage...

Collections of xylem exudate root stumps or detached nodules, and phloem bleeding sap from stems, petioles, fruits were made variously aged plants Lupinus albus L. relying on nodules for their N supply. Sucrose was the major organic solute phloem, asparagine, glutamine, serine, aspartic acid, valine, lysine, isoleucine, leucine, principal solutes both phloem. Xylem exhibited higher relative proportions glutamine acid than sap, but lower other amino acids. Phloem petioles less concentrated in...

Xylem sap and phloem exudates from detached leaves fruit tips were collected analyzed during early pod-fill in nodulated soybeans (Glycine max (L.) Merr. cv Wilkin) grown without (-N) with (+N) NH(4)NO(3). Ureides the predominant (91%) of N transported xylem -N plants, while amides (45%) nitrate (23%) accounted for most +N plants. Amino acids (44%) ureides (36%) major forms exported but (63%) important Based on composition tip phloem, (55% 33%) (26% 47%) majority imported by fruits...

Between 1995 and 2010, the total energy intensity (E/GDP, PJ/Gross Domestic Product in 2002$) of Canadian economy declined by 23% or − 2.64 MJ/$. To understand why, Logarithmic Mean Divisia Index (LMD-I) method was used to decompose a large body government statistical data supporting observed E/GDP decline. The analysis shows that (a) 48% (1.27 MJ/$) decline associated with an inter-sector structural change (i.e. increased contribution GDP low energy-using commercial institutional sector...

Although infected cell O2 concentration (Oi) is known to limit respiration and nitrogenase activity in legume nodules, techniques have not been available measure both processes simultaneously an individual nodule. Consequently, details of the relationship between Oi are fully appreciated. For present study, a probe was designed that allowed open circuit measurements H2 evolution (nitrogenase activity) CO2 (respiration rate) single attached soybean nodule while monitoring fractional...

In the present study we investigated proposal that γ‐aminobutyrate (Gaba) shunt in developing soybean ( Glycine max [L.] Merr.) seeds is associated with hypoxia. The ontogeny and pH profile of enzymes glutamate metabolism (glutamate decarboxylase [EC 4.1.1.15]. Gaba transaminase 2.6.1.19], succinic semialdehyde dehydrogenase 1.2.1.16], 1.4.1.2], glutamate:oxaloacetate 2.6.1.1], glutamate:pyruvate 2.6.1.2] 2‐oxoglutarate complex 1.2.4.2]) hypoxia (alcohol [ADH, EC 1.1.1.1] pyruvate [PDC,...

In N 2 ‐fixing legume nodules, O is required in large amounts for aerobic respiration, yet nitrogenase, the bacterial enzyme that fixes , labile. A high rate of consumptition and a cortical barrier to gas diffusion work together maintain low, non‐inhibitory concentration central, infected zone nodule. At this low concentration, cytosolic leghemoglobin facilitate through cell bacteria. The resistance variable used by nodules regulate cells such it limits respiration fixation at all times....