Symbiotic Nitrogen Fixation by Coralloid Roots of the Cycad Macrozamia riedlei: Physiological Characteristics and Ecological Significance

1976 ◽  
Vol 3 (3) ◽  
pp. 349 ◽  
Author(s):  
J Halliday ◽  
JS Pate
Keyword(s):  
Nitrogenase Activity ◽  
Natural Habitat ◽  
Natural Populations ◽  
Molar Ratio ◽  
Fixation Rate ◽  
Plant Nitrogen ◽  
Blue Green Algae ◽  
C2h2 Reduction ◽  
Whole Plant ◽  
Coralloid Roots

'Coralloid' roots containing blue-green algae occur commonly on the upper root stocks of M. riedlei in natural habitat in Western Australia. Each coralloid mass persists for several seasons; replacement sets form at irregular intervals, especially after fire. 15N2 and acetylene reduction assays demonstrate that coralloid roots fix nitrogen at physiologically significant rates. C2H2 reduction rates by coralloid roots are higher in winter than in summer. Performance is positively correlated with rainfall; soil temperature appears to be of lesser importance. Diurnal fluctuations in nitrogenase activity occur. Calibration using 15N2 gives a molar ratio of C2H2 reduced : N2 fixed of 5.8 : 1. The seasonal average of C2H2 reduction of 14.8 nmol per g fresh wt coralloid root per min is then equivalent to 37.6 g N per kg fresh wt per year, a fixation rate potentially capable of doubling coralloid root nitrogen once in every 8 weeks, and whole plant nitrogen every 8-11 years. Returns of fixed nitrogen in two natural populations of Macrozamia are estimated by compounding measurements of biomass of host and symbiotic organs with the seasonal average for coralloid fixation rate. The values obtained (18.8 and 18.6 kg N ha-1 year-1) indicate that Macrozamia contributes significantly to the nitrogen economy of its ecosystem.

Systemic control of nodule formation by the plant N demand requires autoregulation dependent and independent mechanisms

2021 ◽  
Author(s):  
Marjorie Pervent ◽  
Ilana Lambert ◽  
Marc Tauzin ◽  
Alicia Karouani ◽  
Martha Nigg ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Nodule Formation ◽  
Atmospheric Nitrogen ◽  
Plant Nitrogen ◽  
Systemic Signaling ◽  
Systemic Control ◽  
Whole Plant ◽  
Strong Control ◽  
Mutant Genes ◽  
N Demand

Abstract In legumes interacting with rhizobia the formation of symbiotic organs involved in the acquisition of atmospheric nitrogen is depending of the plant nitrogen (N) demand. We used Medicago truncatula plants cultivated in split-root systems to discriminate between responses to local and systemic N signalings. We evidenced a strong control of nodule formation by systemic N-signaling but obtained no clear evidence of a local control by mineral nitrogen. Systemic signaling of the plant N demand controls numerous transcripts involved in the root transcriptome reprogramming associated to early rhizobia interaction and nodule formation. SUNN has an important role in this control but major systemic N signaling responses remained active in the sunn mutant. Genes involved in the activation of nitrogen fixation are regulated by systemic N signaling in the mutant, explaining why the hypernodulation phenotype is not associated to a higher nitrogen fixation of the whole plant. The control of the transcriptome reprogramming of nodule formation by systemic N signaling requires other pathway(s) that parallel the SUNN/CLE pathway.

Nitrogen fixation

1976 ◽  
Vol 274 (934) ◽  
pp. 341-358 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Metabolic Regulation ◽  
Higher Plants ◽  
Focal Point ◽  
Nitrogenase Activity ◽  
Nitrogen Fixing ◽  
Blue Green Algae ◽  
International Biological Programme ◽  
The 1960S ◽  
Biological Programme

The International Biological Programme served as a focal point for studies on biological nitrogen fixation during the 1960s. The introduction of the acetylene reduction technique for measuring nitrogenase activity in the field led to estimates becoming available of the contribution of lichens, blue-green algae, nodulated non-legumes and bacterial-grass associations, as well as of legumes. Other studies carried out on the physiology and biochemistry of the process led to the eventual purification and characterization of the nitrogenase enzyme. These studies, collectively, provided the springboard for current work, so essential in view of the present energy crisis, on how to increase the use and efficiency of nitrogen-fixing plants, on the metabolic regulation of the nitrogenase enzyme and on the genetics of the nitrogen-fixing process, both in higher plants and in free-living micro-organisms.

Biology of Acacia pulchella R.br. With Special Reference to Symbiotic Nitrogen Fixation

1981 ◽  
Vol 29 (5) ◽  
pp. 579 ◽  
Author(s):  
D Monk ◽  
JS Pate ◽  
WA Loneragan
Keyword(s):  
Plant Density ◽  
Natural Populations ◽  
Growth Period ◽  
Sand Culture ◽  
Nitrogen And Phosphorus ◽  
N Accumulation ◽  
Growing Seasons ◽  
Reduction Activity ◽  
C2h2 Reduction ◽  
Total Plant

Growth, reproduction and longevity of the fire weed Acacia pulchella var. glaberrima were examined in natural populations of known age in coastal sands in and around Perth, W.A. Dense populations (10000 plantsiha) were established after a summer burn; plant density was 30% of its initial value at 4 years. less than 8% at 13 years. Plants accumulated dry matter, nitrogen and phosphorus throughout a 13-year growth period. Seed production commenced at 2 years, reached a maximum (12000 seeds per plant per year) at 3 or 4 years declining to 2000 seedsiplant in the 13th year. Only a small fraction of the shed seed accumulated in soil under the stands. Changes in total plant N, nodule weightlplant, and C2H2 reduction capacity of detached nodules were followed in populations in their first, second and fourth growing seasons. A new set of nodules formed with the autumn rains, peak nodule mass and C2H2 reduction activity were recorded in July-October, and virtually no nodules survived the summer into a second growing season. A glasshouse study of N accumulation and C2H2 reduction by nodules in minus N sand culture gave acalibration value of 2.26 mol C2H2 : mol N2 fixed. Applying this value to data from nativepopulations, 8% of the N accumulated by first season plants, 45% of the N of second season plants and 68% of the N of fourth season plants were estimated to be derived from symbiosis. Average annual returns of N to the ecosystem were estimated at 3.9 kg/ha, probably more than half of this from N2 fixation. Progressive death of plants in the populations gave the greatest return ( 1.9 kg N per ha per yr), the remainder from litter (1 kg N per ha per yr) and shed seed ( 1 kg N per ha per yr).

scholarly journals Rapid Propagation of Sweet and Sour Cherry Rootstocks

2014 ◽  
Vol 42 (2) ◽  
pp. 488-494 ◽  
Author(s):  
DuÅ¡ica DORIC ◽  
Vladislav OGNJANOV ◽  
Mirjana LJUBOJEVIC ◽  
Goran BARAC ◽  
Jovana DULIC ◽  
...  
Keyword(s):  
Natural Habitat ◽  
Natural Populations ◽  
Sour Cherry ◽  
Phenyl Acetate ◽  
Aseptic Culture ◽  
Double Phase ◽  
Rooting Medium ◽  
Phase Medium ◽  
Germplasm Diversity ◽  
Cherry Rootstocks

The paper presents a protocol for micropropagation of Prunus sp. rootstocks included in the sweet and sour cherry breeding program. Germplasm diversity for rootstock breeding derives from natural populations, where conditions and biological vectors for systematic infection with viral diseases are constantly present. The establishment of aseptic culture depends primarily on the explant type, as all selections were collected from natural habitat. For nearly all investigated selections, dormant buds were the favored source, due to enabling rosette initiation in more than 58% cases. In P. cerasus L. selections, 100% contamination was noted when shoot tips were used as an explant source. Significant influence of the double-phase medium on the number and height of multiplied shoots was observed in the standard cherry rootstock, ‘Gisela 6’. For P. fruticosa Pall., selection ‘SV1’ and ‘SV2’, and P. cerasus ‘D6’ selection, the double-phase medium also had a significant effect on the height of multiplied shoots, when compared to solid DKW (Driver and Kuniyuki Walnut) medium. Genetic variability of selections within the investigated species resulted in variable plant rooting success. Adding Fe-EDDHA (Ethylenediamine di-2-hydroxy-phenyl acetate ferric) in the 200 mg l-1 concentration to the rooting medium significantly enhanced the percentage of rooted plants. The highest rooting percentage was noted for ‘Gisela 6’ and ‘D6’ genotype at 1 mgl-1 IBA (indole-3-butyric acid), while 0.8 mgl-1 was the optimum concentration for P. mahaleb L. ‘M1’ selection. P. fruticosa genotypes required significantly higher IBA concentration for rooting (2.5 and 3.5 mg l-1).

Comparison of Chlorophyll a Extractions with Ethanol and Dimethyl Sulfoxide/Acetone, and a Concern about Spectrophotometric Phaeopigment Correction

1992 ◽  
Vol 49 (11) ◽  
pp. 2331-2336 ◽  
Author(s):  
D. J. Webb ◽  
B. K. Burnison ◽  
A. M. Trimbee ◽  
E. E. Prepas
Keyword(s):  
High Pressure ◽  
Dimethyl Sulfoxide ◽  
Chlorophyll A ◽  
Green Algae ◽  
Natural Populations ◽  
Eutrophic Lakes ◽  
North Central ◽  
Chl A ◽  
Blue Green Algae ◽  
Hplc Analyses

Chlorophyll a (Chl a) in water samples from three mesotrophic to eutrophic lakes in north-central Alberta was extracted with one of three solvents (95% ethanol, 90% ethanol, or a 2:3 mixture of dimethyl sulfoxide and 90% acetone (DMSO/acetone)) and analyzed by two techniques (spectrophotometry and high pressure liquid chromatography (HPLC). The dominant phytoplankton were blue-green algae and diatoms. Total Chl a concentrations (i.e. no correction for phaeopigments (Pha)) were not significantly different among solvents (P > 0.5). Total Chl a concentrations from spectrophotometric analyses were significantly higher than those from HPLC analyses (4.2 ± 0.88 and 2.6 ± 0.50 μg∙L−1 respectively, P < 0.05). Pha concentrations derived by spectrophotometry were 64 times higher than those derived by HPLC (1.7 ± 0.52 and 0.025 ± 0.01 μg∙L−1 respectively, P < 0.005). Thus, spectrophotometry appears to dramatically overestimate Pha concentrations and may overestimate total Chl a (i.e. no correction for Pha). Therefore, ethanol and DMSO/acetone are equally suitable for Chl a extraction from natural populations dominated by blue-green algae and/or diatoms, but if information on Pha and/or accessory pigments is required, HPLC analyses are the appropriate route rather than spectrophotometry.

The heterocysts of blue-green algae. III. Differentiation and nitrogenase activity

1972 ◽  
Vol 181 (1063) ◽  
pp. 199-209 ◽  
Keyword(s):  
Nitrogenase Activity ◽  
C:N Ratio ◽  
Free Medium ◽  
Anaerobic Conditions ◽  
Blue Green Algae ◽  
Ammonium N ◽  
Storage Granules ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions ◽  
Heterocyst Development

The course of heterocyst development in Anabacna cylindrica was studied in relation to the ability to fix nitrogen. When non-differentiated filaments, grown in the presence of ammonium-N, were transferred into a medium free from combined nitrogen and incubated under photosynthetic conditions, the cellular C:N ratio increased from 4.5:1 to 8:1 before the percentage heterocyst frequency and nitrogenase activity reached a steady value. The initial stages of differentiation were observed 24 h after transfer into nitrogen-free medium, but nitrogenase activity was only detected when the formation of the first heterocysts was completed. The transformation of a vegetative cell into a heterocyst is characterized by the dissolution of storage granules, the deposition of a multilayered envelope, the breakdown of photosynthetic thylakoids and the formation of new membraneous structures. The latter appear to develop by the coalescence of small newly formed vesicles arising in regions of pre-existing thylakoids. The course of heterocyst development was paralleled by that of nitrogenase activity both under aerobic and anaerobic conditions. Anaerobic incubation enhanced heterocyst production as well as nitrogenase activity. The results suggest that nitrogenase synthesis in Anabaena cylindrica is associated with heterocyst formation and that the primary factor which may regulate both processes is the cellular C:N balance of the alga.

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