Influence of vegetation type and madrone soil inoculum on associative nitrogen fixation in Douglas-fir rhizospheres

1990 ◽  
Vol 20 (3) ◽  
pp. 368-371 ◽  
Author(s):  
M. P. Amaranthus ◽  
C. Y. Li ◽  
D. A. Perry
Keyword(s):  
Acetylene Reduction ◽  
Mycorrhizal Fungi ◽  
Nitrogenase Activity ◽  
Vegetation Type ◽  
Douglas Fir ◽  
Plant Soil ◽  
Soil Systems ◽  
Whole Plant ◽  
Pacific Madrone ◽  
A Site

Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings grown on a site cleared of whiteleaf manzanita (Arctostaphylosviscida Parry) and an adjacent, cleared, annual grass meadow were either inoculated with 100–120 mL per seedling of pasteurized or unpasteurized soil from a nearby Pacific madrone (Arbutusmenziesii Pursh) stand or left uninoculated. After one growing season, Douglas-fir seedling whole-plant soil systems were assayed for nitrogenase activity by the acetylene reduction method. The rate of acetylene reduction in rhizospheres of uninoculated seedlings from the manzanita site (1.40 ± 0.44 nmol•h−1) was significantly higher than that of uninoculated seedlings from the meadow site (0.67 ± 0.15 nmol•h−1). Unpasteurized madrone soil increased the rate of acetylene reduction over 500% for inoculated seedlings grown on the manzanita site, but decreased it by 80% for those grown on the meadow site. The madrone soil influence was apparently biotic: pasteurized, madrone soil did not have a significant effect. No acetylene was reduced in soil without seedlings. Azospirillum sp., a microaerophilic nitrogen (N2) fixing bacterium, was isolated from within the mycorrhizae of inoculated seedlings harvested from the manzanita site. These results suggest that early successional ectomycorrhizal shrubs and hardwood trees may be important in maintaining mycorrhizal fungi and associated N2 fixers after severe disturbance.

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.

Site-to-site variations in nitrogenase activity in a subarctic black spruce forest

1983 ◽  
Vol 13 (5) ◽  
pp. 782-788 ◽  
Author(s):  
Margaret M. Billington ◽  
Vera Alexander
Keyword(s):  
Nitrogen Fixation ◽  
High Latitude ◽  
Acetylene Reduction ◽  
Black Spruce ◽  
Nitrogenase Activity ◽  
Base Line ◽  
Spruce Forest ◽  
Experimental Burn ◽  
Alaskan Arctic ◽  
A Site

An estimate of nitrogen fixation in terms of acetylene reduction was made at two sites in a subarctic black spruce (Piceamariana (Mill.) B.S.P.) forest to determine site-to-site variations. The work was initially done to provide base-line comparative data for the primary intensive site, and for a site preparatory to an experimental burn. The principal conclusions were that, in contrast with the Alaskan arctic coastal tundra, microtopographic variations were not associated with big differences in acetylene reduction. Lichens with nitrogen-fixing phycobionts were an important influence on the activity; however, a high overall proportion of the activity was attributable to the moss cover, at least in part because of associated cyanobacteria. Daily rates for June and July averaged 74, 119 and 109 μg C2H4•m−2•day−1, respectively, for the 3 years. In common with other high-latitude sites, moisture was the major factor controlling nitrogenase activity.

Interaction effects of vegetation type and Pacific madrone soil inocula on survival, growth, and mycorrhiza formation of Douglas-fir

1989 ◽  
Vol 19 (5) ◽  
pp. 550-556 ◽  
Author(s):  
M. P. Amaranthus ◽  
D. A. Perry
Keyword(s):  
Vegetation Type ◽  
Douglas Fir ◽  
Vegetation Types ◽  
Root Tips ◽  
White Oak ◽  
Growth And Survival ◽  
Root Symbionts ◽  
Growth Differences ◽  
Pacific Madrone ◽  
Growth Of Seedlings

Douglas-fir seedlings were planted in cleared blocks within three adjacent vegetation types, whiteleaf manzanita, annual grass meadow, and an open stand of Oregon white oak, in southwest Oregon. Within subplots in each block, either pasteurized or unpasteurized soil from a nearby Pacific madrone stand was transferred to the planting holes of the seedlings; control seedlings received no madrone soil. Second-year survival averaged 92, 43, and 12% for seedlings planted on the manzanita, meadow, and oak sites, respectively. Growth differences generally paralleled survival differences. Added madrone soil, whether pasteurized or unpasteurized, did not influence survival, but growth of seedlings on the manzanita site was substantially increased by the addition of unpasteurized madrone soil. Unpasteurized madrone soil did not influence growth of seedlings in the meadow and the oak stand. Pasteurized madrone soil did not affect growth in any of the vegetation types. When added to the manzanita site, unpasteurized madrone soil nearly tripled the number of mycorrhizal root tips forming on seedlings and resulted in formation of a new mycorrhiza type not seen otherwise. As with growth, unpasteurized madrone soil had little or no effect in the other vegetation types. These results suggest that manzanita and madrone impose on soils a biological pattern that stimulates Douglas-fir growth and survival, and they add to the growing body of literature showing that root symbionts and rhizosphere organisms mediate interactions among plant species.

Estimating Nitrogenase Activity of Faba Bean (Vicia faba) by Acetylene Reduction (Ar) Assay

1990 ◽  
Vol 17 (5) ◽  
pp. 489 ◽  
Author(s):  
Herdina ◽  
JH Silsbury
Keyword(s):  
Diurnal Variation ◽  
Vicia Faba ◽  
Faba Bean ◽  
Closed System ◽  
N2 Fixation ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Electron Flow ◽  
Specific Rate ◽  
Rooting Medium

Methods of conducting acetylene reduction (AR) assay were appraised for estimating the nitrogenase activity of nodules of faba bean (Vicia faba L.). Factors considered were: (i) disturbance of plants when removing the rooting medium; (ii) assay temperature; (iii) the use of whole plants rather than detached, nodulated roots; (iv) diurnal variation in nodule activity; and (v) a decline in C2H4 production after exposure to C2H2. Plants growing in jars of 'oil dry' (calcined clay) had the same AR activity when assayed in situ in a closed system as when assayed after removal of the rooting medium. Assay temperatures of 12.5, 17.5 and 22.5°C influenced the specific rate of AR with the optimum at 17.5°C. Removal of the shoot resulted in a rapid decrease in AR activity in both vegetative and reproductive plants but the effect was much larger in the latter. AR and respiration by nodulated roots were closely linked and both varied markedly over a diurnal 12 h/12 h cycle. Since no fluctuation was found after nodules were detached, diurnal variation in the respiration of nodulated roots is attributed to change in nodule activity. Half of the dark respiration of nodulated roots was associated with respiration of the nodules and thus largely with N2 fixation. Since the AR assay provides no information on how electron flow in vivo is partitioned between reduction of N2 and reduction of protons, diurnal variation in hydrogen evolution (HE) in air and Ar/O2 in an open system was used to estimate this partitioning. Diurnal variation in apparent N2 fixation estimated in this manner was examined at a 'low' PPFD (300 μmol m-2 s-1) and at 'high' (1300 μmol m-2 s-1) to explore whether variation could be attributed to change in carbohydrate supply. Although HE in air and in Ar/O2 were both closely linked with the respiration of the nodulated root, apparent N2 fixation showed only a slight diurnal variation at 'low' light and almost none at 'high'. Vegetative plants showed no C2H2-induced decline in activity with exposure to C2H2 but reproductive plants did. This difference appears to be an age effect rather than attributable to flowering per se, since a decline occurred even when plants were kept vegetative by disbudding. A closed system for AR assay appears satisfactory for vegetative faba bean but such an assay over a 40-min period during the reproductive stage would underestimate nitrogenase activity by about 20%.

Dinitrogen fixation and nodulation by Frankia in Alnus incana as affected by inorganic nitrogen in pot experiments with peat

1983 ◽  
Vol 61 (11) ◽  
pp. 2956-2963 ◽  
Author(s):  
U. Granhall ◽  
T. Ericsson ◽  
M. Clarholm
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Inorganic Nitrogen ◽  
Experimental Period ◽  
Alnus Incana ◽  
Nitrogen Application ◽  
Noticeable Effect ◽  
Essential Nutrients ◽  
Pot Experiments ◽  
Ph Level

The effects of single large or repeated, exponentially increasing applications of nutrients, with or without inorganic nitrogen and at two pH levels, on the growth, nodulation, acetylene reduction, and nutrient uptake in Alnus incana (L.) Moench were investigated in pot experiments with peat under controlled laboratory conditions. The repeated application of inorganic nitrogen did not suppress nitrogenase activity until the last 2 weeks, whereas an initial, large, nitrogen application effectively inhibited nodulation and activity throughout the 40-day experimental period. The mode of nitrogen application was thus found to be more important than the total amounts applied. Shoot length, leaf area, shoot–root relations, dry-matter production, and nitrogen contents of plants were determined at the end of the experiment, as well as the effect of Frankia inoculations. Nitrogenase activity was determined three times, at 0, 3, and 5 weeks. N2 fixation (balance/acetylene reduction) was found to be maximal, 55% of total nitrogen uptake, in minus-N pots with single applications of essential nutrients. The fastest growth was, however, noted in pots with single applications of all nutrients, including N. Among the latter, pots inoculated with Frankia showed the best growth, in spite of low nitrogenase activity. The only noticeable effect of a raised pH level was a reduced endophyte activity in minus-N pots with single applications of essential nutrients, due to increased N mineralization in the peat.

Nitrogen fixation (acetylene reduction) by Klebsiella pneumoniae in association with 'Park' Kentucky bluegrass (Poa pratensis L.)

1981 ◽  
Vol 27 (1) ◽  
pp. 52-56 ◽  
Author(s):  
L. V. Wood ◽  
R. V. Klucas ◽  
R. C. Shearman
Keyword(s):  
Nitrogen Fixation ◽  
Klebsiella Pneumoniae ◽  
Ethylene Production ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Poa Pratensis ◽  
Kentucky Bluegrass ◽  
Surface Sterilization ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Turfs of 'Park' Kentucky bluegrass reestablished in the greenhouse and inoculated with Klebsiella pneumoniae (W6) showed significantly increased nitrogen fixation (acetylene reduction) compared with control turfs. Mean ethylene production rates per pot were 368 nmol h−1 for K. pneumoniae treated turfs, 55 nmol h−1 for heat-killed K. pneumoniae treated turfs, and 44 nmol h−1 for untreated turfs. Calculated lag periods before activity was observed were generally very short (less than 1 h).When 'Park' Kentucky bluegrass was grown from seed on soil-less medium of Turface, a fired aggregate clay, inoculation with K. pneumoniae (W6) resulted in 9 of 11 turfs showing nitrogenase activity (mean ethylene producion rate per pot was 195 nmol h−1). Only 3 of 11 turfs treated with heat-killed K. pneumoniae showed any activity and their mean rate of ethylene production (40 nmol h−1 per pot) was significantly lower than that for turfs treated with K. pneumoniae.Using the 'Park'–Turface soil-less model system it was shown that acetylene reducing activity was (i) root associated, (ii) generally highest at a depth of 1–4 cm below the surface, (iii) enhanced by washing excised roots, and (iv) inhibited by surface sterilization of excised roots. Klebsiella pneumoniae was recovered from Turface and roots showing acetylene reducing activity.

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.

scholarly journals Divergence in bidirectional plant-soil feedbacks between montane annual and coastal perennial ecotypes of yellow monkeyflower (Mimulus guttatus)

2020 ◽  
Author(s):  
Mariah M. McIntosh ◽  
Lorinda Bullington ◽  
Ylva Lekberg ◽  
Lila Fishman
Keyword(s):  
Mycorrhizal Fungi ◽  
Arbuscular Mycorrhizal ◽  
Plant Performance ◽  
Fungal Communities ◽  
Mechanistic Study ◽  
List Type ◽  
Mimulus Guttatus ◽  
Plant Variation ◽  
Plant Soil ◽  
Soil Origin

SUMMARYUnderstanding the physiological and genetic mechanisms underlying plant variation in interactions with root-associated biota (RAB) requires a micro-evolutionary approach. We use locally adapted montane annual and coastal perennial ecotypes of Mimulus guttatus (yellow monkeyflower) to examine population-scale differences in plant-RAB-soil feedbacks.We characterized fungal communities for the two ecotypes in-situ and used a full-factorial greenhouse experiment to investigate the effects of plant ecotype, RAB source, and soil origin on plant performance and endophytic root fungal communities.The two ecotypes harbored different fungal communities and responsiveness to soil biota was highly context-dependent. Soil origin, RAB source, and plant ecotype all affected the intensity of biotic feedbacks on plant performance. Feedbacks were primarily negative, and we saw little evidence of local adaptation to either soils or RAB. Both RAB source and soil origin significantly shaped fungal communities in roots of experimental plants. Further, the perennial ecotype was more colonized by arbuscular mycorrhizal fungi (AMF) than the montane ecotype, and preferentially recruited home AMF taxa.Our results suggest life history divergence and distinct edaphic habitats shape plant responsiveness to RAB and influence specific associations with potentially mutualistic root endophytic fungi. Our results advance the mechanistic study of intraspecific variation in plant–soil–RAB interactions.

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