Carbohydrate Physiology of Ectomycorrhizae

Hacskaylo, Edward

doi:10.1016/b978-0-12-472850-9.50012-8

Cited by 52 publications

(29 citation statements)

References 24 publications

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“…If P fertilization influences the extent of VAM formation through an effect on the availability of metabolites to the fungus, then it is the supply of organic nutrients within the root, not in the rhizosphere, that appears to be critical. Early theories on the effects of soil fertility on ectomycorrhiza formation suggested that the rate of development of the fungal component was related to the concentration of reducing sugars in host root extracts (9). Similar correlations between VAM formation and carbohydrate concentrations in root extracts were reported for subterranean clover (Trifolium subterraneum L.) grown with different rates of P fertilization (13).…”

Section: Discussionsupporting

confidence: 56%

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation

Schwab¹,

Menge²,

Leonard³

1983

Plant Physiol.

121

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A comparison was made of water-soluble root exudates and extracts of Sorghum vulgare Pers. grown under two levels of P nutrition. An increase in P nutrition significantly decreased the concentration of carbohydrates, carboxylic acids, and amino acids in exudates, and decreased the concentration of carboxylic acids in extracts. Higher P did not affect the relative proportions of specific carboxylic acids and had little effect on proportions of specific amino acids in both extracts and exudates. Phosphorus amendment resulted in an increase in the relative proportion of arabinose and a decrease in the proportion of fructose in exudates, but did not have a large effect on the proportion of individual sugars in extracts. The proportions of specific carbohydrates, carboxylic acids, and amino acids varied between exudates and extracts. Therefore, the quantity and composition of root extracts may not be a reliable predictor of the availability of substrate for symbiotic vesicular-arbuscular mycorrhizal fungi. Comparisons of the rate of leakage of compounds from roots with the growth rate of vesicular-arbuscular mycorrhizal fungi suggest that the fungus must either be capable of using a variety of organic substrates for growth, or be capable of inducing a much higher rate of movement of speciflc organic compounds across root cell membranes than occurs through passive exudation as measured in this study.Vesicular-arbuscular mycorrhizal (VAM)2 fungi apparently are obligately dependent on living plant roots for their supply of fixed carbon. Under some conditions, nearly the entire length of a root cortex may be colonized by VAM fungi (11). However, variables such as host species, light, temperature, and host nutrition affect the proportion of root inhabited by the fungal symbiont. Several studies have shown that high levels of P in plant tissue typically reduce the extent of VAM formation (13,19,27). In some experiments, the total length of root colonized by VAM fungi was not decreased with P application, but the proportion of root colonized was reduced due to the stimulation of root growth in high P treatments (4, 29). However, other studies have shown that total fungal growth, as well as proportion ofcolonized root, was reduced with P application (4,28). In comparisons of VAM formation in P-deficient and P-amended roots of sudangrass, the major effect of P on VAM was expressed after initial penetration of the root by the fungus had occurred (28). However, there was no morphological evidence of an active defense 'To whom correspondence should be addressed.2Abbreviation: VAM, vesicular-arbuscular mycorrhiza (1).against the fungus in high P roots. Instead, the overall growth rate ofthe fungus was reduced in the P-amended plants, as would be predicted if increasing concentrations of P reduced the availability of metabolites within the root to the fungus (28). Because the fungus normally does not disrupt the plasma membrane of host cells (6), host products must cross this barrier before they are available to the endoph...

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Section: Discussionsupporting

confidence: 56%

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation

Schwab¹,

Menge²,

Leonard³

1983

Plant Physiol.

121

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“…However, Lewis et al (1994) found no significant correlation between carbohydrate concentration (either total sugars or starch) and mycorrhizal development on loblolly pine seedlings. The positive correlations between below-ground starch concentration and percentage or number of ectomycorrhizas observed in this study reflect overall sink/source trends of the host, while the negative correlation between mycorrhiza and steady-state soluble carbohydrate concentration might reflect changes in demand and use by the fungal symbiont (Hacskaylo, 1973). Understanding sink/source relationships, particularly quantifying the flux of C between above-and below-ground plant tissues, might give a greater understanding of mechanisms regulating mycorrhizal response in elevated-COg environments (Zak et al, 1993;Pregitzer et al, 1995).…”

Section: Discussionmentioning

confidence: 91%

“…Establishment of mycorrhizal infection is dependent upon availability of C in and around plant roots (Hacskaylo, 1973). Elevated atmospheric COg often results in increased below-ground allocation of C .…”

Section: Discussionmentioning

confidence: 99%

Effects of nitrogen and water limitation and elevated atmospheric CO₂on ectomycorrhiza of longleaf pine

et al. 1997

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SUMMARYLongleaf pine {Pinus palustris Mill.) seedlings were exposed to two concentrations of atmospheric COj (365 or 720 fimol mor^) and two levels of N (0-02 or 0-20 mg N g"^ soil yr"^) within open-top chambers for 20 months. Seedlings were adequately watered for 19 wk to ensure seedling establishment, after which two water-stress treatments (target values -0-5 or -1-5 MPa xylem pressure potential) were implemented. Fine-root samples were collected in July and November 1993, and in March and November 1994. Ectomycorrhizal and non-mycorrhizal short roots per unit length of fine root were quantified. The percentage of ectomycorrhizal short roots and numbers of ectomycorrhizas per unit root length were higher for seedlings grown with elevated COg, low N and adequate water. Interactions among main treatment variables demonstrated higher percentages of ectomycorrhizal short roots, fine root length per seedling, and total numbers of ectomycorrhizas per seedling for plants grown with high COg (compared with ambient) or adequate water (compared with water stress) only under high N conditions. Increased fine-root length and ectomycorrhizal colonization under elevated COg resulted in higher (almost double) numbers of ectomycorrhizas per seedling at each sampling.

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“…P. arhizus spore inoculation produces better developed mycorrhiza than inoculation with mycelia, without affecting the seedlings' growth. It is known that carbon metabolites, nutrients, and hormones are redirected from seedlings toward the symbiotic fungus, and that Suillus species have great demands for carbohydrates (Hacskaylo, 1973). If just the initial mycorrhization of roots with S. granulatus had been achieved, where the mycosymbiont had not been well established (using vegetative inoculum at 1:16 and 1:8), it would have influenced the increase of seedling growth.…”

Section: Discussionmentioning

confidence: 99%

Mycorrhization of containerized Pinus nigra seedlings with Suillus granulatus under open field conditions

2012

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Seedling mycorrhization acts as an efficient tool for improving the quality of seedlings. In this study, the effectiveness of Suillus granulatus, originating from Pinus heldreichii forests (Montenegro), to produce containerized ectomycorrhizal seedlings of autochthonous Pinus nigra in open field conditions was investigated. Spore (10 6 , 10 7 , 10 8 ) and vegetative (1:16, 1:8, 1:4) inoculation on ectomycorrhizal formation and seedling growth were tested. Spore and vegetative inoculums of autochthonous Pisolithus arhizus were used in the same trial as additional control treatments.The utilization of vegetative and spore inoculums of autochthonous S. granulatus has proven to be an effective method of obtaining containerized ectomycorrhizal P. nigra seedlings under open field conditions after 11 months. S. granulatus spore inoculations resulted in well developed ectomycorrhiza, decreasing the growth of the P. nigra seedlings in the first growing season. Mycelial inoculations resulted in slightly developed S. granulatus ectomycorrhiza, which increased the growth of the seedlings. Therefore, it would be feasible to use spore inocula of S. granulatus, with 10 6 spores per plant, to produce ectomycorrhizal P. nigra plants on a large scale. Controlled mycorrhizal inoculation of seedlings is not a common practice in Montenegrin and Serbian nurseries; as such, the obtained results will contribute to the enhancement of nursery production of Pinus nigra and other conifers. This also could be assumed as a starting point for many further efforts and investigations with autochthonous fungal and plant material in this region.

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Carbohydrate Physiology of Ectomycorrhizae

Cited by 52 publications

References 24 publications

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation

Effects of nitrogen and water limitation and elevated atmospheric CO₂on ectomycorrhiza of longleaf pine

Mycorrhization of containerized Pinus nigra seedlings with Suillus granulatus under open field conditions

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Carbohydrate Physiology of Ectomycorrhizae

Cited by 52 publications

References 24 publications

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation

Effects of nitrogen and water limitation and elevated atmospheric CO2on ectomycorrhiza of longleaf pine

Mycorrhization of containerized Pinus nigra seedlings with Suillus granulatus under open field conditions

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Effects of nitrogen and water limitation and elevated atmospheric CO₂on ectomycorrhiza of longleaf pine