Phosphate Uptake Zones of Mycorrhizal and Non‐mycorrhizal Onions

Rhodes, L. H.; Gerdemann, J. W.

doi:10.1111/j.1469-8137.1975.tb01419.x

Cited by 211 publications

(89 citation statements)

References 13 publications

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“…Vol. 64,1979 CRESS, THRONEBERRY, AND LINDSEY Previous reports have stated that enhanced absorption of P and therefore better growth of mycorrhizal plants was due to increased absorbing surface and associated soil exploration (6,17,19). Certainly, such an explanation would seem logical.…”

Section: Resultsmentioning

confidence: 96%

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Kinetics of Phosphorus Absorption by Mycorrhizal and Nonmycorrhizal Tomato Roots

Cress¹,

Throneberry²,

Lindsey³

1979

Plant Physiol.

125

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Kinetics of P absorption were investigated in mycorrhizal (Gkmws fascadana) and nonmycorrhizal tomato (Lycopersicon escude_uu) roots to determine why increased ion absorption by mycorrhizae occurs. Initial rates of absorption of "2P were measured at 1 to 100 micromolar KH2PO4 (pH 4.6). Absorption rates of mycorrhizae were about twice those of control roots. Augustnsson-Hofstee analysis yielded two linear phases; V.. and K,. were calculated for each phase. In the low phase (I to 20 micromolar), V..,,S values for the mycorrhizal and nonmycorhizal roots were each 0.10 micromoles P per gram fresh weight per hour while K. values were 1.6 and 3.9 micromolar KH2PO4, respectively. For the high phase (30 to 100 micromolar), V,. vahes for mycorrhizal and nonmycorrhizal roots were 0.32 and 0.25 micromoles P per gram fresh weight per hour and K. values were 35 and 42 micromolar, respectively. These results indicate that at the lower phase concentrations, similar to those expected in most soil solutions, a major factor contributing to the increased uptake was an apparent greater affinty of the absorbing sites for H2PO4-(lower K.).Mycorrhizal plants commonly accumulate more P than do nonmycorrhizal plants, especially when P availability is limited (5,9). Increased absorption is usually attributed to increased surface area and increased soil exploration by the root-fungus association (7,17,19). To our knowledge, the kinetics of ion uptake by mycorrhizae has not been investigated. Information of this type is needed to determine whether enhanced absorption is in fact due solely to increased number of absorbing sites contributed by the fungus, or possibly to greater ion affinity of the fungal absorption sites, or a combination of both factors. Such a kinetic approach to examination of the absorption of P by mycorrhizae is reported here. Tomatoes, known to exhibit a mycorrhizal response in ion uptake (3,18), were used in the investigation. MATERIALS AND METHODS

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Section: Resultsmentioning

confidence: 96%

“…Increased absorption is usually attributed to increased surface area and increased soil exploration by the root-fungus association (7,17,19). To our knowledge, the kinetics of ion uptake by mycorrhizae has not been investigated.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Phosphorus Absorption by Mycorrhizal and Nonmycorrhizal Tomato Roots

Cress¹,

Throneberry²,

Lindsey³

1979

Plant Physiol.

125

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“…This is in spite of conclusive work with both vesicular-arbuscular and ectomycorrhizas showing that external hyphae absorb P and other nutrients (Melin & Nilsson, 1950;Rhodes & Gerdemann, 1975;Cooper & Tinker, 1978). For vesicular-arbuscular mycorrhizas, there have been several estimates of mycorrhizal hyphal lengths suggesting values of approximately 100-200 m hyphae per metre of infected root, though there are some wide difTerences (Smith & Gianinazzi-Pearson, 1988).…”

Section: Introduction Of Host Phosphate Have Been Shown Followingmentioning

confidence: 87%

Phosphorus relationships and production of extrametrical hyphae by two types of willow ectomycorrhizas at different soil phosphorus levels

1990

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SUMMARYThere is much circumstantial evidence for a role of increased P uptake in the growth response of plants to ectomycorrhizas. Full response curves with and without mycorrhizal infection along a P gradient in soil are, however, required to test this hypothesis fully. In this experiment, rooted cuttings of Salix viminalis L. cv. Bowles Hybrid were grown in a 1 :2 mixture by volume of gamma-irradiated soil and sterile sand, with bicarbonateextractable P concentrations of 4, 6, 10, 21, 60 or 90 mg P kg'^. The cuttings were inoculated by mixing peat/vermiculite spawn oiLaccariaproximo (Boud.) Pat., or Thelephora terrestris (Ehrh.) Fr., or autoclaved spawn 1: 5 by volume with the soil: sand mixture. The plants showed a positive growth response to mycorrhizal infection by either fungus at the two lower P levels, and to L. proximo only at 10 mg P kg'^ At 21 mg kg^^ and above, infection was reduced and neither mycorrhizal inoculation nor further P additions caused significant growth increases. These results imply that the growth responses to ectomycorrhizas in this experiment were solely due to increases in P uptake. Cuttings infected with L. proximo tended to be larger than those infected by T. terrestris. Estimates of percent mycorrhizal infection did not diflFer between the fungi at the lower P levels. However, overall production of extramatrical hyphae per gram of soil was highest in soil inoculated with L. proximo. At 10 mg P kg~i the length of L. proximo hyphae per unit length of mycorrhizal root, P uptake per unit root weight, and total P content in plants infected with L. proximo were significantly higher than for T. terrestris. This study confirms that increased P uptake can be an important component of growth stimulation by ectomycorrhizas. It also presents the first quantification of extramatrical ectomycorrhizal hyphae in soil and suggests a role for them m the growth response.

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“…Nevertheless, investigators must measure root length to calculate this variable, so it is more timedemanding-and sometimes less feasible-than measuring PRLC alone. Arbuscular mycorrhizal fungi also produce extraradical hyphae that extend into the surrounding soil much further than do root hairs (Rhodes and Gerdemann 1975;Read 1984;Friese and Allen 1991). These hyphae are responsible for nutrient uptake by AMF from soil, so standing hyphal length in soils is another frequently-used index of AMF biomass (e.g., Bardgett 1991;Sylvia 1992;Schweiger and Jakobsen 2000;Hart and Reader 2002a).…”

Section: How Are Arbuscular Mycorrhizal Fungi Assessed?mentioning

confidence: 99%

The extent of mycorrhizal colonization of roots and its influence on plant growth and phosphorus content

2013

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Aims The most common metric of arbuscular mycorrhizal fungal (AMF) abundance is percent root length colonized (PRLC) by mycorrhizal structures. Frequently, plants with greater PRLC are assumed to receive more nutrients (such as phosphorus, P) from their mycorrhizal symbionts, leading to greater plant growth. Nevertheless, the functional significance of this metric remains controversial. In this review, I discuss whether manipulations of PRLC generally led to changes in plant biomass and P content, and whether AMF taxa and plant functional groups influence these relationships. Methods I conducted a meta-analysis of laboratoryand field-based trials in which mycorrhizal colonization was directly altered compared to unmanipulated controls. For each trial, I calculated (1) the difference in PRLC (ΔPRLC) between the treatments, and (2) the response ratio of plant biomass. In a subset of these studies, the response ratio of P content of host plants could also be calculated. ResultsThe response ratio of plant biomass and P content rose significantly and exponentially as ΔPRLC increased. Nevertheless, ΔPRLC explained only a fraction of the variation in response ratios in each case. Moreover, AMF taxa varied in their effects on biomass per unit ΔPRLC. In addition, plant functional groups differed in effects on plant P content per unit ΔPRLC, with C4 grasses responding most strongly. Conclusions It appears that as the extent to which plant roots are colonized by AMF increases, plant growth and P content often increase, although substantial variability exists among trials. As others have found, a likely mechanism for this relationship is increased transfer of P (and perhaps other nutrients) through the more-prevalent mycorrhizal structures.

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Phosphate Uptake Zones of Mycorrhizal and Non‐mycorrhizal Onions

Cited by 211 publications

References 13 publications

Kinetics of Phosphorus Absorption by Mycorrhizal and Nonmycorrhizal Tomato Roots

Kinetics of Phosphorus Absorption by Mycorrhizal and Nonmycorrhizal Tomato Roots

Phosphorus relationships and production of extrametrical hyphae by two types of willow ectomycorrhizas at different soil phosphorus levels

The extent of mycorrhizal colonization of roots and its influence on plant growth and phosphorus content

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