Symbiotic Vesicular-Arbuscular Mycorrhizae Influence Maximum Rates of Photosynthesis in Tropical Tree Seedlings Grown Under Elevated CO2

1997 ◽  
Vol 24 (2) ◽  
pp. 185 ◽  
Author(s):  
C. E. Lovelock ◽  
D. Kyllo ◽  
M. Popp ◽  
H. Isopp ◽  
A. Virgo ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Arbuscular Mycorrhizae ◽  
Forest Tree ◽  
Sink Strength ◽  
Tree Seedlings ◽  
Va Mycorrhizae ◽  
Co2 Concentrations ◽  
Vesicular Arbuscular ◽  
Mycorrhizal Plants ◽  
Atmospheric Co2 Concentrations

To investigate the importance of phosphorus and carbohydrate concentrations in influencing photosynthetic capacity of tropical forest tree seedlings under elevated CO2, we grew seedlings of Beilschmiedia pendula (Sw.) Hemsl. (Lauraceae) under elevated CO2 concentrations either with or without vesicular-arbuscular (VA) mycorrhizae. VA-mycorrhizae increased phosphorus concentrations in all plant organs (leaves, stems and roots). Maximum rates of photosynthesis (Amax) measured under saturating levels of CO2 and light were correlated with leaf phosphorus concentrations. VA-mycorrhizae also increased leaf carbohydrate concentrations, particularly under elevated CO2, but levels were low and within the range observed in naturally occurring forest species. Root carbohydrate concentrations were reduced in VA-mycorrhizal plants relative to non-mycorrhizal plants. These results indicate an important role for VA-mycorrhizae in controlling photosynthetic rates and sink strength in tropical trees, and thus in determining their response to future increases in atmospheric CO2 concentrations.

Vesicular–arbuscular mycorrhizae in the Chenopodiaceae and Cruciferae: do they occur?

1978 ◽  
Vol 56 (22) ◽  
pp. 2813-2817 ◽  
Author(s):  
Marc C. Hirrel ◽  
H. Mehravaran ◽  
J. W. Gerdemann
Keyword(s):  
Arbuscular Mycorrhizae ◽  
Chenopodium Album ◽  
Mycorrhizal Infection ◽  
Va Mycorrhizae ◽  
Glomus Fasciculatus ◽  
Vesicular Arbuscular ◽  
Companion Plant ◽  
Resistance To Infection ◽  
Companion Plants ◽  
Test Plants

Members of the Chenopodiaceae and Cruciferae were reported to be nonmycorrhizal by early investigators; more recently, some species in these families have been reported to have low or in some cases high levels of vesicular–arbuscular (VA) mycorrhizal infection. In our experiments, a sparse vesicular (chlamydospore) infection by Glomus fasciculatus was found in four species of Chenopodiaceae and two species of Cruciferae but only when grown in the presence of a mycorrhizal companion plant, citrus or onion. No arbuscules were observed in infected roots. Chenopodium album had the highest incidence of infection (5%). Infection was restricted to older tissue and penetration of the vascular cylinder was common, which is atypical of VA mycorrhizae. As hyphae from mycorrhizal companion plants grew through the soil, they encountered older roots of the test plants which probably offered little or no resistance to infection. In documenting the occurrence of VA mycorrhizae in any species, it is important to observe whether the plant is growing by itself or if there are mycorrhizal plants closely associated with it. Also, care should be taken not to confuse common root parasites for the fungal structures of VA mycorrhiza.

scholarly journals Nitrogen inputs and losses in response to chronic CO<sub>2</sub> exposure in a sub-tropical oak woodland

2014 ◽  
Vol 11 (1) ◽  
pp. 61-106 ◽  
Author(s):  
B. A. Hungate ◽  
B. D. Duval ◽  
P. Dijkstra ◽  
D. W. Johnson ◽  
M. E. Ketterer ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Atmospheric Co2 ◽  
15N Tracer ◽  
Carbon Limitation ◽  
N Fixation ◽  
Oak Woodland ◽  
N Losses ◽  
Co2 Concentrations ◽  
Nitrogen Inputs ◽  
Atmospheric Co2 Concentrations

Abstract. Rising atmospheric CO2 concentrations could alter the nitrogen (N) content of ecosystems by changing N inputs and N losses, but responses vary in field experiments, possibly because multiple mechanisms are at play. We measured N fixation and N losses in a subtropical oak woodland exposed to 11 yr of elevated atmospheric CO2 concentrations. We also explored the role of herbivory, carbon limitation, and competition for light and nutrients in shaping response of N fixation to elevated CO2. Elevated CO2 did not significantly alter gaseous N losses, but lower recovery and deeper distribution in the soil of a long-term 15N tracer indicated that elevated CO2 increased leaching losses. Elevated CO2 had no effect on asymbiotic N fixation, and had a transient effect on symbiotic N fixation by the dominant legume. Elevated CO2 tended to reduce soil and plant concentrations of iron, molybdenum, phosphorus, and vanadium, nutrients essential for N fixation. Competition for nutrients and herbivory likely contributed to the declining response N fixation to elevated CO2. These results indicate that positive responses of N fixation to elevated CO2 may be transient, and that chronic exposure to elevated CO2 can increase N leaching. Models that assume increased fixation or reduced N losses with elevated CO2 may overestimate future N accumulation in the biosphere.

Elevated atmospheric CO2 concentrations increase wheat root phosphatase activity when growth is limited by phosphorus

1998 ◽  
Vol 25 (1) ◽  
pp. 87 ◽  
Author(s):  
Damian J. Barrett ◽  
Alan E. Richardson ◽  
Roger M. Gifford
Keyword(s):  
Phosphatase Activity ◽  
Elevated Co2 ◽  
Atmospheric Co2 ◽  
Organic P ◽  
Wheat Seedlings ◽  
P Deficiency ◽  
Co2 Concentrations ◽  
Wide Range ◽  
Atmospheric Co2 Concentrations ◽  
Ambient Co2

Wheat seedlings were grown in solution culture under adequate and limited phosphorus treatments at current ambient and elevated (approximately 2× ambient) CO2 concentrations. Acid phosphomonoesterase (‘phosphatase’) activity of root segments was measured using p-nitrophenyl phosphate as substrate. When plant growth was P-limited, elevated CO2 concentrations increased phosphatase activity more than at ambient CO2. This result (1) was evident when expressed on a unit root dry weight or root length basis, indicating that increased root enzyme activity was unlikely to be associated with CO2-induced changes in root morphology; (2) occurred when plants were grown aseptically, indicating that the increase in phosphatase activity originated from root cells rather than root- associated microorganisms; (3) was associated with shoot P concentrations below 0.18%; (4) occurred only when wheat roots were grown under P deficiency but not when a transient P deficiency was imposed; and (5) suggest that a previously reported increase in phosphatase activity at elevated CO2 by an Australian native pasture grass (Gifford, Lutze and Barrett 1996; Plant and Soil 187, 369–387) was also a root mediated response. The observed increase in phosphatase activity by plant roots at elevated CO2, if confirmed for a wide range of field pasture and crop species, is one factor which may increase mineralisation of soil organic P as the anthropogenic increase of atmospheric CO2 concentrations continues. But, whether a concomitant increase in plant uptake of P occurs will depend on the relative influence of root and microbial phosphatases, and soil geochemistry in determining the rate of mineralisation of soil organic P for any given soil.

scholarly journals 165 VESICULAR-ARBUSCULAR MYCORRHIZAE DECREASE DAYS TO FLOWERING AND INCREASE INFLORESCENCE NUMBER OF GERANIUM `SPRINTER SCARLET' GROWN IN THREE SOILLESS MEDIA.

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 452d-452 ◽  
Author(s):  
Peter M. Shaw ◽  
Rita Hummel
Keyword(s):  
Arbuscular Mycorrhizae ◽  
The Other ◽  
Days To Flowering ◽  
Soilless Media ◽  
Vesicular Arbuscular Mycorrhizae ◽  
Vesicular Arbuscular ◽  
Mycorrhizal Plants ◽  
Lateral Branches

The effects of vesicular-arbuscular mycorrhizae (VAM) on the growth and flowering of Geranium `Sprinter Scarlet' in three greenhouse soilless media were investigated. All media proved to be well suited for geranium growth and VAM had no significant effect on most vegetative parameters. However, VAM significantly reduced the number of days to flowering of plants grown in Mycori-Mix and Sunshine Aggregate #4 by 6.4 and 6.6 days respectively. Plants grown in Mycori-Mix with VAM flowered 99.4 days after sowing, significantly sooner than those grown in the other media with VAM. Mycorrhizal plants in Mycori-Mix and Metro Mix had a greater number of lateral branches >5 cm in length than non-mycorrhizal in the same media. Regardless of VAM treatment, plants grown in Mycori-Mix had a greater number of visible inflorescences at harvest than the other two media.

Effects of water availability, nitrogen supply and atmospheric CO2 concentrations on plant nitrogen natural abundance values

2006 ◽  
Vol 33 (3) ◽  
pp. 219 ◽  
Author(s):  
William D. Stock ◽  
John R. Evans
Keyword(s):  
Stomatal Conductance ◽  
Water Supply ◽  
Elevated Co2 ◽  
Water Availability ◽  
Atmospheric Co2 ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations ◽  
Cape Gooseberry ◽  
Foliar Δ15n ◽  
Leaf N

The relative effects of soil N, water supply and elevated atmospheric CO2 on foliar δ15N values were examined. Phalaris arundinacea L. (Holdfast) and Physalis peruviana L. (Cape Gooseberry) were grown for 80 d with three water availability treatments, two atmospheric CO2 concentrations and four N supply rates. Elevated CO2 increased total plant biomass and N for each treatment and decreased allocation to roots, leaf N concentrations and stomatal conductance. Leaves had less negative leaf δ13C values under low water supply associated with decreased stomatal conductance and increased leaf N concentration, which decreased the ratio of intercellular to ambient CO2 concentration. The δ15N value of the supplied nitrate (4.15‰) was similar to the value for Phalaris leaves (4.11‰), but Cape Gooseberry leaves were enriched (6.52‰). The effects of elevated CO2 on leaf δ15N values were small, with Phalaris showing no significant change, while Cape Gooseberry showed a significant (P < 0.05) decline of 0.42 ‰. Variation in δ15N values was unrelated to stomatal conductance, transpiration, differential use of N forms or denitrification. Plants with low foliar N concentrations tended to be depleted in 15N. We suggest that changes in N allocation alter foliar δ15N values under different CO2 and water treatments.

scholarly journals Nitrogen inputs and losses in response to chronic CO<sub>2</sub> exposure in a subtropical oak woodland

2014 ◽  
Vol 11 (12) ◽  
pp. 3323-3337 ◽  
Author(s):  
B. A. Hungate ◽  
B. D. Duval ◽  
P. Dijkstra ◽  
D. W. Johnson ◽  
M. E. Ketterer ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Atmospheric Co2 ◽  
15N Tracer ◽  
Carbon Limitation ◽  
N Fixation ◽  
Oak Woodland ◽  
N Losses ◽  
Co2 Concentrations ◽  
Nitrogen Inputs ◽  
Atmospheric Co2 Concentrations

Abstract. Rising atmospheric CO2 concentrations may alter the nitrogen (N) content of ecosystems by changing N inputs and N losses, but responses vary in field experiments, possibly because multiple mechanisms are at play. We measured N fixation and N losses in a subtropical oak woodland exposed to 11 years of elevated atmospheric CO2 concentrations. We also explored the role of herbivory, carbon limitation, and competition for light or nutrients in shaping the response of N fixation to elevated CO2. Elevated CO2 did not significantly alter gaseous N losses, but lower recovery and deeper distribution in the soil of a long-term 15N tracer indicated that elevated CO2 increased leaching losses. Elevated CO2 had no effect on nonsymbiotic N fixation, and had a transient effect on symbiotic N fixation by the dominant legume. Elevated CO2 tended to reduce soil and plant concentrations of iron, molybdenum, phosphorus, and vanadium, nutrients essential for N fixation. Competition for nutrients and herbivory likely contributed to the declining response of N fixation to elevated CO2. These results indicate that positive responses of N fixation to elevated CO2 may be transient and that chronic exposure to elevated CO2 can increase N leaching. Models that assume increased fixation or reduced N losses with elevated CO2 may overestimate future N accumulation in the biosphere.

Vesicular-arbuscular mycorrhizae (VAM) improve phosphorus and zinc nutrition and growth of pigeonpea in a Vertisol

1991 ◽  
Vol 42 (5) ◽  
pp. 835 ◽  
Author(s):  
NP Wellings ◽  
AH Wearing ◽  
JP Thompson
Keyword(s):  
Root Rot ◽  
Arbuscular Mycorrhizae ◽  
Agricultural Practices ◽  
Dry Weight ◽  
Vam Fungi ◽  
P Concentration ◽  
Zn Concentration ◽  
Vesicular Arbuscular ◽  
Vam Colonization ◽  
Mycorrhizal Plants

In a glasshouse trial, pigeonpea (Cajanus cajan) was grown in a Vertisol from the Darling Downs, Qld. The experimental design included two rates of inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi (nil and inoculated), three rates of phosphorus (P) application and two of zinc (Zn), and inoculation (nil and inoculated) with a recently discovered pathogen of pigeonpea, Phytophthora drechsleri Tucker (Pdr). lnoculation with the pathogen was included in the factorial design to investigate any effect of VAM on root rot. Plants responded to inoculation with VAM fungi, showing that the growth of pigeonpea is highly dependent upon mycorrhizal colonization of its root system. The mycorrhizal plants yielded, on average, 3.3 times the dry weight of the non-mycorrhizal plants. Shoot dry weight and Zn concentration of the shoots were both exponentially related to per cent VAM colonization of the root length ( R2 values of 0.904 and 0.644 respectively) and P concentration was linearly related to VAM colonization (R2 = 0.888). VAM increased P concentration, P uptake, Zn concentration, Zn uptake and P/Zn ratio, indicating enhanced growth through improved P and to a lesser extent Zn nutrition. Zinc fertilizer (15 mg kg-1 soil) without Phytophthora inoculation was fungitoxic to the mycorrhizae, decreasing per cent VAM colonization and depressing plant growth. lnoculation with Pdr did not result in infection and root rot symptoms. However, it did overcome the Zn toxicity, possibly through organic chelation effects, and thereby enhanced VAM colonization. Greatest VAM colonization and best plant nutrition and growth were obtained with the combination of VAM inoculation, Pdr inoculation, Zn (15 mg kg-1) and P (10 mg kg-1). Our results indicate the importance of maintaining adequate levels of VAM fungi in soil through appropriate agricultural practices in order to maximize pigeonpea growth.

Pest and disease abundance and dynamics in wheat and oilseed rape as affected by elevated atmospheric CO2 concentrations

2013 ◽  
Vol 40 (2) ◽  
pp. 125 ◽  
Author(s):  
Viktoriya Oehme ◽  
Petra Högy ◽  
Jürgen Franzaring ◽  
Claus P. W. Zebitz ◽  
Andreas Fangmeier
Keyword(s):  
Elevated Co2 ◽  
Oilseed Rape ◽  
Spring Wheat ◽  
Co2 Enrichment ◽  
Plant Phenology ◽  
Plant Diseases ◽  
Atmospheric Co2 ◽  
Pest Species ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

Future atmospheric CO2 concentrations are predicted to increase, and directly affect host plant phenology, which, in turn, is assumed to mediate the performance of herbivorous insects indirectly as well as the abundance and epidemiology of plant diseases. In a 4-year field experiment, spring wheat (Triticum aestivum L. cv. Triso) and spring oilseed rape (Brassica napus L. cv. Campino) were grown using a mini- free-air CO2 enrichment (FACE) system, which consisted of a control (CON), an ambient treatment (AMB) and FACE treatments. The CON and AMB treatments did not receive additional CO2, whereas the FACE plots were moderately elevated by 150 μL L–1 CO2. The impact of elevated CO2 was examined with regard to plant phenology, biomass, leaf nitrogen and carbon, abundance of insect pest species and their relative population growth by either direct counts or yellow sticky traps. Occurrence and damage of plants by pathogens on spring wheat and oilseed rape were directly assessed. Disease infestations on plants were not significantly different between ambient and elevated CO2 in any of the years. Plant phenology, aboveground biomass, foliar nitrogen and carbon concentrations were also not significantly affected by CO2 enrichment. In contrast, the abundance of some species of insects was significantly influenced by elevated CO2, showing either an increase or a decrease in infestation intensity.

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