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Carbon dioxide enrichment and nitrogen fertilization effects on cotton (Gossypium hirsutum L.) plant residue chemistry and decomposition (2000)

Booker, Fitzgerald L. ; Shafer, Steven R. ; Wei, Cai-Miao ; [et al.]

Springer

Plant and soil 220 (2000), S. 89-98

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ISSN: 1573-5036

Keywords: Carbohydrates ; CO2 ; lignin ; nitrogen ; proanthocyanidins ; soil respiration

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Increased atmospheric carbon dioxide (CO2) concentration will likely cause changes in plant productivity and composition that might affect soil decomposition processes. The objective of this study was to test to what extent elevated CO2 and N fertility-induced changes in residue quality controlled decomposition rates. Cotton (Gossypium hirsutum L.) was grown in 8-l pots and exposed to two concentrations of CO2 (390 or 722 μmol mol-1) and two levels of N fertilization (1.0 or 0.25 g l-1 soil) within greenhouse chambers for 8 wks. Plants were then chemically defoliated and air-dried. Leaf, stem and root residues were assayed for total non-structural carbohydrates (TNC), lignin (LTGA), proanthocyanidins (PA), C and N. Respiration rates of an unsterilized sandy soil (Lakeland Sand) mixed with residues from the various treatments were determined using a soda lime trap to measure CO2 release. At harvest, TNC and PA concentrations were 17 to 45% higher in residues previously treated with elevated CO2 compared with controls. Leaf and stem residue LTGA concentrations were not significantly affected by either the elevated CO2 or N fertilization treatments, although root residue LTGA concentration was 30% greater in plants treated with elevated CO2. The concentration of TNC in leaf residues from the low N fertilization treatment was 2.3 times greater than that in the high N fertilization treatment, although TNC concentration in root and stem residues was suppressed 13 to 23% by the low soil N treatment. PA and LTGA concentrations in leaf, root and stem residues were affected by less than 10% by the low N fertilization treatment. N concentration was 14 to 44% lower in residues obtained from the elevated CO2 and low N fertilization treatments. In the soil microbial respiration assay, cumulative CO2 release was 10 to 14% lower in soils amended with residues from the elevated CO2 and low N fertility treatments, although treatment differences diminished as the experiment progressed. Treatment effects on residue N concentration and C:N ratios appeared to be the most important factors affecting soil microbial respiration. The results of our study strongly suggest that, although elevated CO2 and N fertility may have significant impact on post-harvest plant residue quality of cotton, neither factor is likely to substantially affect decomposition. Thus, C cycling might not be affected in this way, but via simple increases in plant biomass production.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004773404948

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Influence of Phenolic acids on microbial populations in the rhizosphere of cucumber (1991)

Shafer, Steven R. ; Blum, Udo

Springer

Journal of chemical ecology 17 (1991), S. 369-389

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ISSN: 1573-1561

Keywords: Allelopathy ; ferulic acid ; p-courmaric acid ; vanillic acid ; Cucumis sativus ; bacteria ; fungi

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Experiments were conducted to determine whether changes in soil microbial populations that occur in response to additions of certain allelopathic phenolic acids to bulk soil also occur in the rhizosphere. Cucumber seedlings were transplanted into cups containing a nutrient-enriched mixture of Portsmouth B1, soil and sand and were watered five times (once every 48 hr) with aqueous solutions of ferulic,p-coumaric, or vanillic acid (each at 0, 0.25, or 0.50μol/g soil material). Nutrient solution was applied on alternate days. Leaf growth was suppressed by up to 42% by phenolic acids, but changes in root growth varied with the compound and concentration in solution. Significant increases (over 600% relative to controls) in populations of fast-growing bacteria in the rhizosphere were detected after two but not after five treatments, and increases (400% relative to controls) in numbers of fungal propagules were detected after five treatments. Such increases suggested that chronic exposure to a phenolic acid might resuit in high populations of rhizosphere microorganisms that could metabolize the compounds and thus alter observable responses by the plant. To test this, plants were watered repeatedly with a low-concentration solution of ferulic acid (chronic treatments; 0.0 or 0.1μmol/g soil material in one experiment, 0.000 or 0.025μimol/g soil material in a second) and then once with a highconcentration solution (acute treatment; 0.0, 0.5, or 1.0μmol/g soil material in the first experiment; 0.000, 0.125, or 0.250μmol/g soil material in the second).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00994339

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Induction and/or Selection of Phenolic Acid-Utilizing Bulk-Soil and Rhizosphere Bacteria and Their Influence on Phenolic Acid Phytotoxicity (2000)

Blum, Udo ; Staman, Karen L. ; Flint, Laura J. ; [et al.]

Springer

Journal of chemical ecology 26 (2000), S. 2059-2078

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ISSN: 1573-1561

Keywords: Allelopathy ; bulk-soil and rhizosphere bacteria ; Cucumis ; phenolic acid mixtures ; phytotoxicity

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Bulk-soil and rhizosphere bacteria are thought to exert considerable influence over the types and concentrations of phytotoxins, including phenolic acids, that reach a root surface. Induction and/or selection of phenolic acid-utilizing (PAU) bacteria within the bulk-soil and rhizosphere have been observed when soils are enriched with individual phenolic acids at concentrations ≥0.25 μmol/g soil. However, since field soils frequently contain individual phenolic acids at concentrations well below 0.1 μmol/g soil, the actual importance of such induction and/or selection remains uncertain. Common bacteriological techniques (e.g., isolation on selective media, and plate dilution frequency technique) were used to demonstrate in Cecil Ap soil systems: (1) that PAU bacterial communities in the bulk soil and the rhizosphere of cucumber seedlings were induced and/or selected by mixtures composed of individual phenolic acids at concentrations well below 0.25 μmol/g soil; (2) that readily available carbon sources other than phenolic acids, such as glucose, did not modify induction and/or selection of PAU bacteria; (3) that the resulting bacterial communities readily utilize mixtures of phenolic acids as a carbon source; and (4) that depending on conditions (e.g., initial PAU bacterial populations, and phenolic acid concentration) there were significant inverse relationships between PAU bacteria in the rhizosphere of cucumber seedlings and absolute rates of leaf expansion and/or shoot biomass. The decline in seedling growth could not be attributed to resource competition (e.g., nitrogen) between the seedlings and the PAU bacteria in these studies. The induced and/or selected rhizosphere PAU bacteria, however, reduced the magnitude of growth inhibition by phenolic acid mixtures. For a 0.6 μmol/g soil equimolar phenolic acid mixture composed of p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid, modeling indicated that an increase of 500% in rhizosphere PAU bacteria would lead to an approximate 5% decrease (e.g., 20–25%) in inhibition of absolute rates of leaf expansion. As far as we know, this is the first time that such a relationship has been quantified.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005560214222

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Influence of a mycorrhizal fungus and/or rhizobium on growth and biomass partitioning of subterranean clover exposed to ozone (1997)

Miller, Joseph E. ; Shafer, Steven R. ; Schoeneberger, Michele M. ; [et al.]

Springer

Water, air & soil pollution 96 (1997), S. 233-248

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ISSN: 1573-2932

Keywords: rhizobia ; VAM

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract The influence of soilborne symbionts such as rhizobia or mycorrhizal fungi on plant response to ozone (O3) has not been well defined. Leguminous plants in the field are infected by both types of organisms, which influence plant nutrition and growth. We studied the effects of infection withRhizobium leguminosarum biovartrifolii and/orGigaspora margarita on response of subterranean clover (Trifolium subterraneum L. cv Mt. Barker) to O3. Exposures were conducted in greenhouse CSTR chambers using four O3 concentrations [charcoal-filtered (CF), 50, 100, or 150 ppb; 6 h day−1, 5 day wk−1 for 12 weeks] as main plots (replicated). Four inoculum types were subplot treatments, i.e., inoculated with one, both, or neither microorganisms. At 2-wk intervals, plants were exposed to14CO2 and harvested 24 h later for determination of biomass and14C content of shoots and roots. Ozone at 100 or 150 ppb suppressed clover growth during the experiment. Inoculation withG. margarita alone suppressed clover growth by the last two harvests, whereasR. leguminosarum alone enhanced growth during this time period. When both symbionts were present, the plants grew similarly to the noninoculated controls. Shoot/root ratios were increased by 100 or 150 ppb O3 compared to that for CF-treated plants. Shoot/root ratios were greater for all inoculated plants compared to noninoculated controls. Under low O3 stress (CF or 50 ppb), plants inoculated with bothR. leguminosarum andG. margarita transported a greater proportion of recent photosynthate (14C) to roots than did noninoculated plants; we attribute this to metabolic requirements of the microorganisms. At the highest level of O3 stress (150 ppb), this did not occur, probably because little photosynthate was available and the shoots retained most of it for repair of injury. Statistically significant interactions occurred between O3 and inoculum types for shoot and total biomass. When averaged across harvests, 50 ppb O3 suppressed biomass in the plants inoculated withG. margarita alone. Apparently, the mycorrhizal fungus is such a significant C drain that even a small amount of O3 stress suppresses plant growth under these conditions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02407207

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INFLUENCE OF A MYCORRHIZAL FUNGUS AND/OR RHIZOBIUM ON GROWTH AND BIOMASS PARTITIONING OF SUBTERRANEAN CLOVER EXPOSED TO OZONE (1997)

MILLER, JOSEPH E. ; SHAFER, STEVEN R. ; SCHOENEBERGER, MICHELE M. ; [et al.]

Springer

Water, air & soil pollution 96 (1997), S. 233-248

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ISSN: 1573-2932

Keywords: rhizobia ; VAM

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract The influence of soilborne symbionts such as rhizobia or mycorrhizal fungi on plant response to ozone (O3) has not been well defined. Leguminous plants in the field are infected by both types of organisms, which influence plant nutrition and growth. We studied the effects of infection with Rhizobium leguminosarum biovar trifolii and/or Gigaspora margarita on response of subterranean clover (Trifolium subterraneum L. cv Mt. Barker) to O3. Exposures were conducted in greenhouse CSTR chambers using four O3 concentrations [charcoal-filtered (CF), 50, 100, or 150 ppb; 6 h day-1, 5 day wk-1 for 12 weeks] as main plots (replicated). Four inoculum types were subplot treatments, i.e., inoculated with one, both, or neither microorganisms. At 2-wk intervals, plants were exposed to 14CO2 and harvested 24 h later for determination of biomass and 14C content of shoots and roots. Ozone at 100 or 150 ppb suppressed clover growth during the experiment. Inoculation with G. margarita alone suppressed clover growth by the last two harvests, whereas R. leguminosarum alone enhanced growth during this time period. When both symbionts were present, the plants grew similarly to the noninoculated controls. Shoot/root ratios were increased by 100 or 150 ppb O3 compared to that for CF-treated plants. Shoot/root ratios were greater for all inoculated plants compared to noninoculated controls. Under low O3 stress (CF or 50 ppb), plants inoculated with both R. leguminosarum and G. margarita transported a greater proportion of recent photosynthate (14C) to roots than did noninoculated plants; we attribute this to metabolic requirements of the microorganisms. At the highest level of O3 stress (150 ppb), this did not occur, probably because little photosynthate was available and the shoots retained most of it for repair of injury. Statistically significant interactions occurred between O3 and inoculum types for shoot and total biomass. When averaged across harvests, 50 ppb O3 suppressed biomass in the plants inoculated with G. margarita alone. Apparently, the mycorrhizal fungus is such a significant C drain that even a small amount of O3 stress suppresses plant growth under these conditions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1026496420809

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