Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their... more Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their function in these environments. We conducted greenhouse experiments to study the effects of AM fungal assemblages-collected from different vegetation communities in a Florida wetland-under free-drained and flooded conditions, and at three phosphorus (P) levels on growth and P nutrition of Typha latifolia L. and Panicum hemitomon Schult. We also studied the effects of flooding on the spread of extraradical hyphae from P. hemitomon roots. For both plants no AM fungal assemblage had a consistent effect on plant growth and P nutrition. For T. latifolia, flooding nearly eliminated AM fungal colonization and, in the free-drained treatments, P amendment suppressed colonization. Furthermore, colonization by some mycorrhizal assemblages increased shoot-and root-P concentrations, but there were no significant plant growth responses. For P. hemitomon, the mycorrhizal association was suppressed by flooding and P amendment but, among the fungal assemblages, there were differences in root colonization. Mycorrhizal colonization improved some plant-growth and P-nutrition parameters at lower P levels relative to nonmycorrhizal controls, but generally conferred no benefit or was detrimental at higher P levels. Extraradical hyphae of most assemblages were restricted by flooding to 2.5 cm, though differences among AM fungal assemblages occurred with a maximum observed extension of 16.5 cm. We conclude that the impact of the mycorrhizal association on these wetland plants was a function of the complex interactions among the AM fungal assemblages, plant species, water condition, and P level. Future studies should focus on understanding the species composition of the assemblages, and potential adaptation to wetland conditions among these fungal species.
Go to AGRIS search. ASA special publication. (1992). Vesicular-arbuscular mycorrhizae ... Languag... more Go to AGRIS search. ASA special publication. (1992). Vesicular-arbuscular mycorrhizae ... Language, English. Notes, references. In the series analytic: Mycorrhizae in Sustainable Agriculture. Type, Directory. Journal Title, ASA special publication. ISSN, 0066-0566. Vol. No. p. 101-124 ...
Plants must be established quickly on replenished beaches in order to stabilize the sand and begi... more Plants must be established quickly on replenished beaches in order to stabilize the sand and begin the dune-building process. The objective of this research was to determine whether inoculation of sea oats (Uniola paniculata L.) with bacteria (indigenous rhizosphere bacteria and N(2) fixers) alone or in combination with vesicular-arbuscular mycorrhizal fungi would enhance plant growth in beach sand. At two fertilizer-N levels, Klebsiella pneumoniae and two Azospirillum spp. did not provide the plants with fixed atmospheric N; however, K. pneumoniae increased root and shoot growth. When a sparingly soluble P source (CaHPO(4)) was added to two sands, K. pneumoniae increased plant growth in sand with a high P content. The phosphorus content of shoots was not affected by bacterial inoculation, indicating that a mechanism other than bacterially enhanced P availability to plants was responsible for the growth increases. When sea oats were inoculated with either K. pneumoniae or Acaligenes...
For efficient handling, vesicular-arbuscular mycorrhizal fungi should be processed into small and... more For efficient handling, vesicular-arbuscular mycorrhizal fungi should be processed into small and uniform inocula; however, processing can reduce the inoculum density. In this article we describe the preparation and use of sheared-root inocula of Glomus spp. in which inoculum densities were increased during processing. Our objectives were to determine inoculum viability and density after shearing and to ascertain if the sheared inocula could be pelletized or used with a gel carrier. Root samples were harvested from aeroponic cultures, blotted dry, cut into 1-cm lengths, and sheared in a food processor for up to 80 s. After shearing, the inoculum was washed over sieves, and the propagule density in each fraction was determined. Sheared inocula were also encapsulated in carrageenan or used in a gel carrier. Shearing aeroponically produced root inocula reduced particle size. Propagule density increased with decreasing size fraction down to a size of 63 mum, after which propagule densit...
We acknowledge the contribution of H. E. Wilcox to the design of the wick-culture system. We than... more We acknowledge the contribution of H. E. Wilcox to the design of the wick-culture system. We thank W. J. Bloomberg for isolate T841 of Fusarium oxysporum, L. F. Grand for isolate T1036 of Laccaria laccata, the Weyerhaeuser Company for Douglas-fir seed, and A. 0. Larsen and H. H. Lyon for technical help.
To better understand the behavior of selected vesicular-arbuscular mycorrhizal (VAM) isolates in ... more To better understand the behavior of selected vesicular-arbuscular mycorrhizal (VAM) isolates in the field, we documented the growth of roots, root hairs, and VAM colonization of inoculated and noninoculated sweet potato plants (Ipomea batatas (L.) Lam. cv White Star) over a growing season. We also determined the seasonal dynamics of P and Zn uptake, and shoot and storage-root growth. Shoot cuttings were inoculated with an isolate of either Glomus etunicatum Becker and Gerdemann or Acaulospora rugosa Mortan, or were not inoculated, and were harvested 2, 4, 8, 13, 20, and 27 weeks after planting (WAP). At each harvest, roots were sampled at 0 to 30, 30 to 60, and 60 to 90cm depths and at 0, 23, 83, and 116 cm from the base of the shoot. At the end of the study, the roots of three noninoculated plants were sampled by soil horizon. Inoculation had no affect on shoot growth or total shoot uptake of P and Zn; shoot dry mass and P and Z content increased rapidly up to 20 WAP, while shoot length continued to increase through 27 WAP. Shoot-P concentration of plants inoculated with A. rugosa at 2 and 8 WAP were higher than the noninoculated plants, while shoot-Zn concentration was not affected by inoculation. Storage-root yields of inoculated plants were higher than yields for noninoculated plants. Root length density, and percentage of root length with root hairs and VAM colonization were highest and most dynamic near the base of the plant. Percentage of root length colonization by VAM fungi was highest in the E2 horizon, intermediate in the Bh horizon, and lowest in the Ap horizon. Percentage of root length with root hairs had the opposite pattern. Intensive measurements of root characteristics close to the base of the plant, and shoot P-content and concentration during the period of rapid yield production, provided the most useful data for evaluating the activity of effective isolates.
Colonization of roots and soil by arbuscular mycorrhizal (AM) fungi sometimes promotes stomatal c... more Colonization of roots and soil by arbuscular mycorrhizal (AM) fungi sometimes promotes stomatal conductance (gs) of the host plant, but scientists have had difficulty predicting or manipulating the response. Our objective was to test whether the magnitude of AM influence on gs is related to environmental conditions: irradiance, air temperature or leaf temperature. Stomatal conductances of two groups of uncolonized sorghum plants were compared to gs of plants colonized by Glomus intraradices (Gi) or Gigaspora margarita (Gm) in 31 morning and afternoon periods under naturally varying greenhouse conditions. Stomatal conductance of Gi and Gm plants was often markedly higher than gs of similarly sized nonAM plants. AM promotion of gs was minimal at the lowest irradiances and lowest air and leaf temperatures, but was substantial at intermediate irradiance and temperatures. AM promotion was again low or absent at the highest irradiances and temperatures. Magnitude of AM promotion of gs was not a function of absolute gs. Promotion of gs by Gi and Gm was remarkably similar. Differing phosphorus fertilization did not affect gs.
Micropropagation technology promises to improve the supply of sea oats for restoring Florida's er... more Micropropagation technology promises to improve the supply of sea oats for restoring Florida's eroded beaches, but concerns about genetic diversity need to be addressed. These dune plants are colonized by a wide array of arbuscular mycorrhizal (AM) fungi, yet little is know of the diversity of these fungal communities. Our goal was to test the level of functional diversity that exists among communities of AM fungi that are present in divergent Florida dunes. Community pot cultures were established from samples collected from ten transects in two Gulf coast and two Atlantic coast locations in Florida, and these were used to conduct two greenhouse studies. The objective of the first study was to evaluate withinlocation variance in the mycorrhizal function of different AM fungal communities associated with endemic sea oats. The objective of the second study was to evaluate among-location responses of plant and fungal ecotypes using selected combinations obtained from the first experiment. Within locations, the AM fungal community had significant impacts on shoot mass and shoot-P contents, confirming a range of symbiotic effectiveness exists within the beach-dune system. Among locations, there was a tendency for greater root colonization between host clones and fungal communities from the same location, indicating a degree of specificity between host ecotypes and their symbiotic fungi. Relative to plant growth response, one fungal community was superior across plant genotypes from all locations, while one plant genotype tended to have the best response across all fungal communities. These data suggest that while it is possible to select effective AM fungal-host combinations for outplanting, origin of host and AM fungi have little predictive value in screening these combinations.
Our objective was to evaluate the ability of an ectomycorrhizal fungus to alter the competitive i... more Our objective was to evaluate the ability of an ectomycorrhizal fungus to alter the competitive interaction of pine seedlings growing with grass, and to determine whether the interaction was modified by soil-phosphorus (P) concentration. Slash pine (Pinus elliottii), inoculated with the ectomycorrhizal fungus Pisolithus arhizus or fortuitously colonized by Thelephora terrestris, and a native grass (Panicum chamaelonche) were grown in a greenhouse at three P levels (0.32, 3.22, 32.26 mM H 3 PO 4). Pine inoculated with P. arhizus took up more P when competing with the nonmycorrhizal grass than when competing with another pine (irrespective of pine mycorrhizal status). Phosphorus uptake kinetics (C min , the minimum concentration at which P can be absorbed from a solution; I max , the maximum uptake rate) for pine and grass were also determined under hydroponic conditions. Pine had a higher I max than grass but grass had a lower C min , suggesting that pine is more competitive at higher nutrient concentrations while grass is more competitive at lower nutrient concentrations. The controlled conditions used in these experiments allowed us to evaluate specific parameters (P uptake and absorbing surface area) affecting plant competition.
Mineralization is the dominant process controlling soil-solution P in the Spodosols of the southe... more Mineralization is the dominant process controlling soil-solution P in the Spodosols of the southeastern United States. Pine trees growing in these soils are typically colonized by ectomycorrhizal (EM) fungi that are known to produce phosphatases. Little, however, is known of the dynamics of EM short roots or phosphatase activity in tree plantations. To address this question, short root densities, EM
ferent uptake kinetics, faster extension rate, chemical alteration of the rhizosphere-hyphosphere... more ferent uptake kinetics, faster extension rate, chemical alteration of the rhizosphere-hyphosphere, increased Chinese brake fern (Pteris vittata L.) is a hyperaccumulator of arfunctional longevity, mineralization of organic forms, senic (As) that grows naturally on soils in the southern United States. exploration of smaller pore spaces, greater carbon-use It is reasonable to expect that mycorrhizal symbiosis may be involved in As uptake by this fern. This is because arbuscular mycorrhizal (AM) efficiency, and differences in associated rhizosphere fungi have a well-documented role in increasing plant phosphorus (P) populations (O'Keefe and Sylvia, 1991). uptake, P and As have similar chemical properties, and ferns are known Ferns are known to be colonized by AM fungi (Berch to be colonized by AM fungi. We conducted a factorial greenhouse ex
Responses of somatic embryos of sweet potato (Ipomoea batata (L.) Poir., cv. White Star) at diffe... more Responses of somatic embryos of sweet potato (Ipomoea batata (L.) Poir., cv. White Star) at different developmental stages to in vitro inoculation with Glomus etunicatum (Becker and Gerdemann) (isolate INVAM FL329) were evaluated. Somatic embryos were grown in glass tubes containing sterilized vermiculite and sand. A layer of natrosol plus White's medium was used as a carrier for arbuscular mycorrhizal (AM) fungal spores. Survival of embryos inoculated with AM fungi was significantly (P < 0.05) greater than that of noninoculated embryos at the rooted-cotyledonary-torpedo and rooted-elongated-torpedo developmental stages. Mycorrhizae significantly (P < 0.05) increased plantlet formation only when inoculation occurred at the rooted-elongated-torpedo developmental stage. The growth stage at which the embryos were inserted into the glass tubes exerted a significant influence upon plantlet formation, and plantlet formation was further enhanced by inoculation with G. etunicatum....
The vesicular–arbuscular mycorrhizal (VAM) status of Myrica cerifera L. (wax myrtle) was investig... more The vesicular–arbuscular mycorrhizal (VAM) status of Myrica cerifera L. (wax myrtle) was investigated under greenhouse and field conditions. Myrica cerifera and Paspalum notatum Flügge (bahiagrass) were grown in inter- and intra-specific plant combinations with and without VAM fungi. Roots of field-collected M. cerifera were also examined for colonization by VAM fungi. Myrica cerifera became colonized by VAM fungi only in the presence of a VAM colonized grass plant; however, arbuscules were consistently lacking. VAM fungi had no effect on root or shoot growth of M. cerifera. When grown in the presence of P. notatum, shoot growth of M. cerifera was reduced, regardless of inoculation treatment. Colonization of field-collected M. cerifera roots ranged from 0 to 75%; however, nearly all samples lacked arbuscules. Unexpectedly, samples from wet sites had the highest colonization levels. Failure of M. cerifera to become colonized when grown without a VAM companion plant and the absence of...
Arbuscular mycorrhizal (AM) grasses compete for nutrients with ectomycorrhizal (EM) pine in the s... more Arbuscular mycorrhizal (AM) grasses compete for nutrients with ectomycorrhizal (EM) pine in the southeastern United States. Our objective was to determine if benomyl could be used to selectively inhibit the function of AM and thereby reduce grass competition in the field. The effects of Benlate (active ingredient: benomyl) in the greenhouse and field were evaluated. No effect was observed on
Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their... more Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their function in these environments. We conducted greenhouse experiments to study the effects of AM fungal assemblages-collected from different vegetation communities in a Florida wetland-under free-drained and flooded conditions, and at three phosphorus (P) levels on growth and P nutrition of Typha latifolia L. and Panicum hemitomon Schult. We also studied the effects of flooding on the spread of extraradical hyphae from P. hemitomon roots. For both plants no AM fungal assemblage had a consistent effect on plant growth and P nutrition. For T. latifolia, flooding nearly eliminated AM fungal colonization and, in the free-drained treatments, P amendment suppressed colonization. Furthermore, colonization by some mycorrhizal assemblages increased shoot-and root-P concentrations, but there were no significant plant growth responses. For P. hemitomon, the mycorrhizal association was suppressed by flooding and P amendment but, among the fungal assemblages, there were differences in root colonization. Mycorrhizal colonization improved some plant-growth and P-nutrition parameters at lower P levels relative to nonmycorrhizal controls, but generally conferred no benefit or was detrimental at higher P levels. Extraradical hyphae of most assemblages were restricted by flooding to 2.5 cm, though differences among AM fungal assemblages occurred with a maximum observed extension of 16.5 cm. We conclude that the impact of the mycorrhizal association on these wetland plants was a function of the complex interactions among the AM fungal assemblages, plant species, water condition, and P level. Future studies should focus on understanding the species composition of the assemblages, and potential adaptation to wetland conditions among these fungal species.
Go to AGRIS search. ASA special publication. (1992). Vesicular-arbuscular mycorrhizae ... Languag... more Go to AGRIS search. ASA special publication. (1992). Vesicular-arbuscular mycorrhizae ... Language, English. Notes, references. In the series analytic: Mycorrhizae in Sustainable Agriculture. Type, Directory. Journal Title, ASA special publication. ISSN, 0066-0566. Vol. No. p. 101-124 ...
Plants must be established quickly on replenished beaches in order to stabilize the sand and begi... more Plants must be established quickly on replenished beaches in order to stabilize the sand and begin the dune-building process. The objective of this research was to determine whether inoculation of sea oats (Uniola paniculata L.) with bacteria (indigenous rhizosphere bacteria and N(2) fixers) alone or in combination with vesicular-arbuscular mycorrhizal fungi would enhance plant growth in beach sand. At two fertilizer-N levels, Klebsiella pneumoniae and two Azospirillum spp. did not provide the plants with fixed atmospheric N; however, K. pneumoniae increased root and shoot growth. When a sparingly soluble P source (CaHPO(4)) was added to two sands, K. pneumoniae increased plant growth in sand with a high P content. The phosphorus content of shoots was not affected by bacterial inoculation, indicating that a mechanism other than bacterially enhanced P availability to plants was responsible for the growth increases. When sea oats were inoculated with either K. pneumoniae or Acaligenes...
For efficient handling, vesicular-arbuscular mycorrhizal fungi should be processed into small and... more For efficient handling, vesicular-arbuscular mycorrhizal fungi should be processed into small and uniform inocula; however, processing can reduce the inoculum density. In this article we describe the preparation and use of sheared-root inocula of Glomus spp. in which inoculum densities were increased during processing. Our objectives were to determine inoculum viability and density after shearing and to ascertain if the sheared inocula could be pelletized or used with a gel carrier. Root samples were harvested from aeroponic cultures, blotted dry, cut into 1-cm lengths, and sheared in a food processor for up to 80 s. After shearing, the inoculum was washed over sieves, and the propagule density in each fraction was determined. Sheared inocula were also encapsulated in carrageenan or used in a gel carrier. Shearing aeroponically produced root inocula reduced particle size. Propagule density increased with decreasing size fraction down to a size of 63 mum, after which propagule densit...
We acknowledge the contribution of H. E. Wilcox to the design of the wick-culture system. We than... more We acknowledge the contribution of H. E. Wilcox to the design of the wick-culture system. We thank W. J. Bloomberg for isolate T841 of Fusarium oxysporum, L. F. Grand for isolate T1036 of Laccaria laccata, the Weyerhaeuser Company for Douglas-fir seed, and A. 0. Larsen and H. H. Lyon for technical help.
To better understand the behavior of selected vesicular-arbuscular mycorrhizal (VAM) isolates in ... more To better understand the behavior of selected vesicular-arbuscular mycorrhizal (VAM) isolates in the field, we documented the growth of roots, root hairs, and VAM colonization of inoculated and noninoculated sweet potato plants (Ipomea batatas (L.) Lam. cv White Star) over a growing season. We also determined the seasonal dynamics of P and Zn uptake, and shoot and storage-root growth. Shoot cuttings were inoculated with an isolate of either Glomus etunicatum Becker and Gerdemann or Acaulospora rugosa Mortan, or were not inoculated, and were harvested 2, 4, 8, 13, 20, and 27 weeks after planting (WAP). At each harvest, roots were sampled at 0 to 30, 30 to 60, and 60 to 90cm depths and at 0, 23, 83, and 116 cm from the base of the shoot. At the end of the study, the roots of three noninoculated plants were sampled by soil horizon. Inoculation had no affect on shoot growth or total shoot uptake of P and Zn; shoot dry mass and P and Z content increased rapidly up to 20 WAP, while shoot length continued to increase through 27 WAP. Shoot-P concentration of plants inoculated with A. rugosa at 2 and 8 WAP were higher than the noninoculated plants, while shoot-Zn concentration was not affected by inoculation. Storage-root yields of inoculated plants were higher than yields for noninoculated plants. Root length density, and percentage of root length with root hairs and VAM colonization were highest and most dynamic near the base of the plant. Percentage of root length colonization by VAM fungi was highest in the E2 horizon, intermediate in the Bh horizon, and lowest in the Ap horizon. Percentage of root length with root hairs had the opposite pattern. Intensive measurements of root characteristics close to the base of the plant, and shoot P-content and concentration during the period of rapid yield production, provided the most useful data for evaluating the activity of effective isolates.
Colonization of roots and soil by arbuscular mycorrhizal (AM) fungi sometimes promotes stomatal c... more Colonization of roots and soil by arbuscular mycorrhizal (AM) fungi sometimes promotes stomatal conductance (gs) of the host plant, but scientists have had difficulty predicting or manipulating the response. Our objective was to test whether the magnitude of AM influence on gs is related to environmental conditions: irradiance, air temperature or leaf temperature. Stomatal conductances of two groups of uncolonized sorghum plants were compared to gs of plants colonized by Glomus intraradices (Gi) or Gigaspora margarita (Gm) in 31 morning and afternoon periods under naturally varying greenhouse conditions. Stomatal conductance of Gi and Gm plants was often markedly higher than gs of similarly sized nonAM plants. AM promotion of gs was minimal at the lowest irradiances and lowest air and leaf temperatures, but was substantial at intermediate irradiance and temperatures. AM promotion was again low or absent at the highest irradiances and temperatures. Magnitude of AM promotion of gs was not a function of absolute gs. Promotion of gs by Gi and Gm was remarkably similar. Differing phosphorus fertilization did not affect gs.
Micropropagation technology promises to improve the supply of sea oats for restoring Florida's er... more Micropropagation technology promises to improve the supply of sea oats for restoring Florida's eroded beaches, but concerns about genetic diversity need to be addressed. These dune plants are colonized by a wide array of arbuscular mycorrhizal (AM) fungi, yet little is know of the diversity of these fungal communities. Our goal was to test the level of functional diversity that exists among communities of AM fungi that are present in divergent Florida dunes. Community pot cultures were established from samples collected from ten transects in two Gulf coast and two Atlantic coast locations in Florida, and these were used to conduct two greenhouse studies. The objective of the first study was to evaluate withinlocation variance in the mycorrhizal function of different AM fungal communities associated with endemic sea oats. The objective of the second study was to evaluate among-location responses of plant and fungal ecotypes using selected combinations obtained from the first experiment. Within locations, the AM fungal community had significant impacts on shoot mass and shoot-P contents, confirming a range of symbiotic effectiveness exists within the beach-dune system. Among locations, there was a tendency for greater root colonization between host clones and fungal communities from the same location, indicating a degree of specificity between host ecotypes and their symbiotic fungi. Relative to plant growth response, one fungal community was superior across plant genotypes from all locations, while one plant genotype tended to have the best response across all fungal communities. These data suggest that while it is possible to select effective AM fungal-host combinations for outplanting, origin of host and AM fungi have little predictive value in screening these combinations.
Our objective was to evaluate the ability of an ectomycorrhizal fungus to alter the competitive i... more Our objective was to evaluate the ability of an ectomycorrhizal fungus to alter the competitive interaction of pine seedlings growing with grass, and to determine whether the interaction was modified by soil-phosphorus (P) concentration. Slash pine (Pinus elliottii), inoculated with the ectomycorrhizal fungus Pisolithus arhizus or fortuitously colonized by Thelephora terrestris, and a native grass (Panicum chamaelonche) were grown in a greenhouse at three P levels (0.32, 3.22, 32.26 mM H 3 PO 4). Pine inoculated with P. arhizus took up more P when competing with the nonmycorrhizal grass than when competing with another pine (irrespective of pine mycorrhizal status). Phosphorus uptake kinetics (C min , the minimum concentration at which P can be absorbed from a solution; I max , the maximum uptake rate) for pine and grass were also determined under hydroponic conditions. Pine had a higher I max than grass but grass had a lower C min , suggesting that pine is more competitive at higher nutrient concentrations while grass is more competitive at lower nutrient concentrations. The controlled conditions used in these experiments allowed us to evaluate specific parameters (P uptake and absorbing surface area) affecting plant competition.
Mineralization is the dominant process controlling soil-solution P in the Spodosols of the southe... more Mineralization is the dominant process controlling soil-solution P in the Spodosols of the southeastern United States. Pine trees growing in these soils are typically colonized by ectomycorrhizal (EM) fungi that are known to produce phosphatases. Little, however, is known of the dynamics of EM short roots or phosphatase activity in tree plantations. To address this question, short root densities, EM
ferent uptake kinetics, faster extension rate, chemical alteration of the rhizosphere-hyphosphere... more ferent uptake kinetics, faster extension rate, chemical alteration of the rhizosphere-hyphosphere, increased Chinese brake fern (Pteris vittata L.) is a hyperaccumulator of arfunctional longevity, mineralization of organic forms, senic (As) that grows naturally on soils in the southern United States. exploration of smaller pore spaces, greater carbon-use It is reasonable to expect that mycorrhizal symbiosis may be involved in As uptake by this fern. This is because arbuscular mycorrhizal (AM) efficiency, and differences in associated rhizosphere fungi have a well-documented role in increasing plant phosphorus (P) populations (O'Keefe and Sylvia, 1991). uptake, P and As have similar chemical properties, and ferns are known Ferns are known to be colonized by AM fungi (Berch to be colonized by AM fungi. We conducted a factorial greenhouse ex
Responses of somatic embryos of sweet potato (Ipomoea batata (L.) Poir., cv. White Star) at diffe... more Responses of somatic embryos of sweet potato (Ipomoea batata (L.) Poir., cv. White Star) at different developmental stages to in vitro inoculation with Glomus etunicatum (Becker and Gerdemann) (isolate INVAM FL329) were evaluated. Somatic embryos were grown in glass tubes containing sterilized vermiculite and sand. A layer of natrosol plus White's medium was used as a carrier for arbuscular mycorrhizal (AM) fungal spores. Survival of embryos inoculated with AM fungi was significantly (P < 0.05) greater than that of noninoculated embryos at the rooted-cotyledonary-torpedo and rooted-elongated-torpedo developmental stages. Mycorrhizae significantly (P < 0.05) increased plantlet formation only when inoculation occurred at the rooted-elongated-torpedo developmental stage. The growth stage at which the embryos were inserted into the glass tubes exerted a significant influence upon plantlet formation, and plantlet formation was further enhanced by inoculation with G. etunicatum....
The vesicular–arbuscular mycorrhizal (VAM) status of Myrica cerifera L. (wax myrtle) was investig... more The vesicular–arbuscular mycorrhizal (VAM) status of Myrica cerifera L. (wax myrtle) was investigated under greenhouse and field conditions. Myrica cerifera and Paspalum notatum Flügge (bahiagrass) were grown in inter- and intra-specific plant combinations with and without VAM fungi. Roots of field-collected M. cerifera were also examined for colonization by VAM fungi. Myrica cerifera became colonized by VAM fungi only in the presence of a VAM colonized grass plant; however, arbuscules were consistently lacking. VAM fungi had no effect on root or shoot growth of M. cerifera. When grown in the presence of P. notatum, shoot growth of M. cerifera was reduced, regardless of inoculation treatment. Colonization of field-collected M. cerifera roots ranged from 0 to 75%; however, nearly all samples lacked arbuscules. Unexpectedly, samples from wet sites had the highest colonization levels. Failure of M. cerifera to become colonized when grown without a VAM companion plant and the absence of...
Arbuscular mycorrhizal (AM) grasses compete for nutrients with ectomycorrhizal (EM) pine in the s... more Arbuscular mycorrhizal (AM) grasses compete for nutrients with ectomycorrhizal (EM) pine in the southeastern United States. Our objective was to determine if benomyl could be used to selectively inhibit the function of AM and thereby reduce grass competition in the field. The effects of Benlate (active ingredient: benomyl) in the greenhouse and field were evaluated. No effect was observed on
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