Nitrogenase Activity and Associated Carbon Budgets in Seedlings of Acacia mangium Measured With a Flow-Through System of the Acetylene Reduction Assay

1992 ◽  
Vol 19 (2) ◽  
pp. 97 ◽  
Author(s):  
JS Sun ◽  
RJ Simpson ◽  
R Sands
Keyword(s):  
Acetylene Reduction ◽  
Root Respiration ◽  
Nitrogenase Activity ◽  
Acacia Mangium ◽  
Maintenance Respiration ◽  
Carbon Cost ◽  
Gas System ◽  
Reduction Assay ◽  
Flow Through ◽  
Nodulated Root

Following introduction of acetylene into the flow-through gas system, nitrogenase activity of young seedlings of Acacia mangiurn Willd. increased during the initial gas mixing period but declined thereafter. Nitrogenase-linked respiration also declined rapidly for 3-4 min and slowly thereafter following introduction of acetylene. Seedlings of 12-42 weeks showed a decline in nitrogenase-linked respiration of 15-40%. Nitrogenase activity and nodulated root respiration declined further when the oxygen concentration in the gas flowing past the nodules was reduced. These concomitant declines in nodulated root respiration and nitrogenase activity were used to explore the relation between nodulated root respiration and nitrogenase activity, and to provide an estimate of the carbon cost of nitrogenase activity, and the growth and maintenance respiration of nodulated roots. The carbon cost of nitrogenase activity was 2-8 μmol CO2 μmol-1 C2H2 reduced for young seedlings (12-20 weeks) and was lower (1.3) for older seedlings (30-42 weeks). Nitrogenase activity was 1.2 μmol C2H4 g-1 nod. dw min-1 for plants at 12 weeks, but was 0.3 μmol C2H4 g-1 nod. dw min-1 for plants at 42 weeks after transplanting. The proportion of nitrogenase-linked respiration in nodulated root respiration also declined rapidly with plant age, being 70% at 12 weeks and only 6% at 42 weeks after transplanting.

Physiological acclimations to chilling temperature in symbiotically grown alfalfa

1989 ◽  
Vol 67 (2) ◽  
pp. 352-359 ◽  
Author(s):  
F. D. H. Macdowall ◽  
D. B. Layzell ◽  
K. B. Walsh ◽  
A. S. Denes
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Cold Treatment ◽  
Rest Period ◽  
Net Photosynthesis ◽  
Temperature Profiles ◽  
Whole Plant ◽  
Flow Through ◽  
Nodulated Root ◽  
Whole Plants

An apparent shoot rest period was induced in the 2nd month of growth of alfalfa (Medicago sativa L.) seedlings by a drop in growth temperature from 25:20 °C to 10:7 °C. After prolonged chilling the shoots were replaced by new shoots. Temperature profiles of nodulated root respiration and nitrogenase activity (acetylene reduction and H2 evolution) were measured simultaneously in experiments with a flow-through gassing system during 3 months of cold treatment. Net photosynthesis of whole plants was measured in a closed system. More than half the total initial nitrogenase activity and relative efficiency (RE) were lost during the rest period and recovered during regrowth. Acetylene reduction by chilled plants was insensitive to temperature in the 5 – 15 °C range, unlike the temperature dependence of respiration and H2 evolution in air. In all temperature profiles of RE the RE was highest at 5 – 10 °C. The RE was minimum 10 – 15 °C during the rest period. The optimum temperature for whole plant net photosynthesis also declined to 10 – 15 °C during chilling and it later flattened out in the cold-acclimated regrowth. Possible mechanisms are discussed.

scholarly journals Studies on nitrogenase activity of diazotrophic isolates from different rice production systems

2016 ◽  
Vol 8 (1) ◽  
pp. 284-289
Author(s):  
S. Kanimoli ◽  
K. Kumar
Keyword(s):  
Acetylene Reduction ◽  
Tamil Nadu ◽  
Production Systems ◽  
Nitrogenase Activity ◽  
Rice Production ◽  
Lowland Rice ◽  
Aerobic Rice ◽  
Marked Variation ◽  
Reduction Assay ◽  
First Time

The present study was carried out to evaluate the nitrogen fixing ability of diazotrophs isolated from the rhizosphere soils of rice which were grown in three different rice growing systems. A total of hundred and ten isolates obtained were subjected to Acetylene Reduction Assay (ARA) and ninety eight isolates recorded significant amount of nitrogenase activity in a range of 185.73 to 3794.55 nmoles of ethylene mg of protein-1 h-1. The highest nitrogenase activity was recorded by Derxia (3794.55 nmoles of ethylene mg of protein-1 h-1) isolated from Trichy (lowland). Among the three different rice production systems, isolates obtained from lowland rice (Derxia – 3794.5 nmoles of ethylene mg of protein-1 h-1) recorded higher nitrogenase activity followed by Aerobic (Pseudomonas - 2194.89 nmoles of ethylene mg of protein-1 h-1) and SRI (Azotobacter - 1971.85 nmoles of ethylene mg of protein-1 h-1) rice isolates. The results revealed marked variation in the ARA of the diazotrophic isolates obtained from lowland, SRI and Aerobic rice. The nitrogenase activity of diazotrophs from rice fields have been reported earlier but the nitrogenase activity of diazotrophs from three different rice production systems from various parts of Tamil Nadu is reported for the first time from India.

Nitrogenase Activity by Subterranean Clover and Other Temperate Pasture Legumes

1988 ◽  
Vol 15 (5) ◽  
pp. 657 ◽  
Author(s):  
AG Davey ◽  
RJ Simpson
Keyword(s):  
Root Respiration ◽  
Nitrogenase Activity ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Acetylene Reduction Activity ◽  
Diffusion Resistance ◽  
Pasture Legumes ◽  
Reduction Activity ◽  
Decline Rate ◽  
Nodulated Root

Nitrogenase (C2H2-reduction) activity and nodulated root respiration of intact plants of subterranean clover (Trifolium subterraneum L.) cv. Seaton Park nodulated by Rhizobium trifolii WU95 were measured in a flow-through system. Simultaneous declines in nitrogenase activity and respiration were exhibited 2 min after 10% C2H2 had been introduced into the gas stream. Declines in nitrogenase activity and nodulated root respiration provided an estimate of the efficiency of nitrogenase activity (mol CO2 evolved/mol C2H4 produced). The pre-decline rate of nitrogenase activity at time zero was thus calculated as the product of the respiration associated with nitrogenase activity and the reciprocal of the efficiency of nitrogenase activity. Pre-decline rates of nitrogenase activity were similar to peak rates for several pasture legumes. However, post-decline rates of activity were as much as 70% lower than the pre-decline rate. The age of subterranean clover plants had an important influence on the magnitude of the C2H2-induced decline; young plants exhibited the largest C2H2-induced inhibition of nitrogenase activity. Neither sainfoin (Onobrychis viciifolia Scop.) cv. Othello nodulated by Rhizobium sp. CC1108 nor yellow serradella (Ornithopus compressus L.) cv. Pitman nodulated by R. lupini WU425 exhibited C2H2-induced declines in nitrogenase activity. Nitrogenase-linked respiration of subterranean clover at the 14-leaf stage accounted for 50% of total nodulated root respiration. The oxygen diffusion resistance of the nodules increased in the presence of C2H2 but the effect was reversible once C2H2 was removed from the gas atmosphere. The pre-decline rate of acetylene reduction activity of subterranean clover reached a maximum at 10% C2H2. The C2H2-induced decline in nitrogenase activity was lower at subsaturating pC2H2 and was not detected at 0.4% C2H2.

scholarly journals Factors Influencing Nitrogenase Activity (Acetylene Reduction) by Root Nodules of Groundnut, Arachis hypogaea L.

1983 ◽  
Vol 10 (1) ◽  
pp. 26-29 ◽  
Author(s):  
P. T. C. Nambiar ◽  
P. J. Dart
Keyword(s):  
Soil Moisture ◽  
Environmental Factors ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Activity Period ◽  
Diurnal Fluctuation ◽  
Factors Influencing ◽  
Arachis Hypogaea L ◽  
Reduction Assay

Abstract Acetylene reduction assay, used to measure nitrogenase activity of legume root nodules, is influenced by environmental factors, which limit its application. The effects of some of the environmental factors on acetylene reduction by groundnut root nodules are described. The activity was nonlinear during the first hour of incubation. Assay temperature above 25 C decreased the activity. Washing the nodulated roots prior to the assay also decreased the activity. The activity was influenced by light intensity, soil moisture, and moisture content in the incubation bottle. Diurnal fluctuation with one maximum and one minimum activity period during a 24 hour cycle was observed. Nitrogenase activity was higher during the postrainy season compared to that of the rainy season. A virginia cultivar Kadiri-71 had higher nitrogenase activity than a dwarf valencia cultivar, MH 2.

The effect of four new Frankia isolates on growth and nitrogenase activity in clones of Alnusrubra and Alnussinuata

1984 ◽  
Vol 14 (5) ◽  
pp. 701-706 ◽  
Author(s):  
Carolyn V. Carpenter ◽  
Linda R. Robertson ◽  
John C. Gordon ◽  
David A. Perry
Keyword(s):  
Plant Growth ◽  
Acetylene Reduction ◽  
Growth Parameters ◽  
Nitrogenase Activity ◽  
National Forest ◽  
Root Weight ◽  
Stem Height ◽  
Host Genotype ◽  
Red Alder ◽  
Reduction Assay

Two clones of red alder (Alnusrubra Bong) and two clones of Sitka alder (Alnussinuata (Regel) Rydb) were inoculated with four new Frankia isolates. The endophytes included a red and a Sitka alder isolate from Vancouver Island, British Columbia, and a red and a Sitka alder isolate from Mount Hood National Forest, Oregon. All inoculated ramets were well nodulated and had an active nitrogenase system as measured by the acetylene reduction assay. For the inoculated red alder clones, host genotype had a significant effect on stem height and root weight. None of the growth parameters was affected by endophyte strain or by clone–endophyte interaction. For Sitka alder clones, host genotype affected all growth variables. While endophyte strain had no effect on plant growth, clone–endophyte interaction occurred with stem height and leaf weight. Conversely, acetylene reduction values were not affected by clone or clone–endophyte interaction in either species. In red alder, acetylene reduction values were significantly affected by endophyte strain showing both inter- and intra-species variations. In Sitka alder, endophyte strain did not affect acetylene reduction values. The results indicate that both host genotype and endophyte may affect the efficiency of host–endophyte symbioses.

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