Influence of increasing soil phosphorus levels on interactions between vesicular–arbuscular mycorrhizae and <i>Rhizobium</i> in soybeans

Asimi, Sailimuhan; Gianinazzi‐Pearson, Vivienne; Gianinazzi, Silvio

doi:10.1139/b80-253

Cited by 120 publications

(52 citation statements)

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“…At 0"4 mmol phosphate per kg, these differences were accompanied by very much more activity of nitrate reductase in both roots and shoots of mycorrhizal plants compared with non-mycorrhizal plants at the same phosphate level. These results can be compared with those of Asimi et al (1980) on growth, nodulation and nitrogen fixation in soybeans for they pointed out that the mycorrhizal effect on plant growth was eliminated by improved phosphate nutrition before similar effects on nodulation and nitrogen fixation disappeared. Direct involvement of the fungi in the formation of nodules and assimilation of nitrogen was not in question.…”

Section: Discussionmentioning

confidence: 95%

“…Increased concentration of nitrogen in tissues or increased nitrogen content per plant has been observed in some mycorrhizal legumes assimilating nitrogen via nitrogenase, compared with non-mycorrhizal plants (e.g. Smith and Daft, 1977;Asimi et al, 1980). Further experiments, particularly with non-legumes or non-nodulating legumes, will be required to determine whether increased activity of nitrate reductase in mycorrhizal plants leads to similar increases in nitrogen content in plants assimilating nitrate.…”

Section: Discussionmentioning

confidence: 99%

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ACTIVITY OF NITRATE REDUCTASE IN TRIFOLJUMSUBTERRANEUM: EFFECTS OF MYCORRHIZAL INFECTION AND PHOSPHATE NUTRITION

et al. 1983

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SUMMARYActivity of nitrate reductase (NADH-dependent), measured by in vitro methods, was present in both roots and shoots of non-mycorrhizal Trifolium subterraneum. As expected, the activity was dependent upon the amount of nitrate supplied and was closely related to the concentration of nitrate in the tissues.Mycorrhizal plants had a greater capacity to synthesize the enzyme in both roots and shoots than non-mycorrhizal plants when both were grown under phosphate-limiting conditions. This conclusion was reached from the results of two types of experiment: (1) when constant (relatively low) amounts of nitrate were supplied to the plants each day, the specific activity of the enzyme in the roots declined over the period ofthe experiment (52 days) as the plants grew larger. There was also a decline in shoots of mycorrhizal plants. However, when the nitrate supply was increased fourfold, the stimulation of activity was considerably greater in the roots of mycorrhizal plants than in non-mycorrhizal plants; (2) interactions between mycorrhizal infection, phosphate nutrition and nitrate reductase activity were investigated in plants which received different amounts of nitrate according to size. At the two lowest levels of additional soil phosphate (0 and 0-2 mmol phosphate per kg), there was a large mycorrhizal growth response accompanied by reduction in root: shoot ratio, increase in the phosphate concentration in the tissues and considerable stimulation of nitrate reductase activity, both on fresh weight and whole plant bases. This stimulation (together with changes in root:shoot ratio and phosphate concentration) was also apparent at 0-4 mmol phosphate per kg in the absence of any overall mycorrhizal growth response. At 0-67 mmol phosphate per kg, there was neither a growth response nor any stimulation of enzyme activity.NADPH-dependent nitrate reductase activity, more characteristic of fungi than NADHdependent activity, was barely detectable and similar (very low) activity was present in both mycorrhizal and non-mycorrhizal roots. The conclusions are that mycorrhizal effects on nitrate reductase activity are largely indirect, mediated via improved phosphate nutrition and that direct involvement of the fungi in nitrate assimilation is likely to be very slight.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

ACTIVITY OF NITRATE REDUCTASE IN TRIFOLJUMSUBTERRANEUM: EFFECTS OF MYCORRHIZAL INFECTION AND PHOSPHATE NUTRITION

et al. 1983

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“…The N 2 -fixing abilities of legumes can be enhanced not only by Rhizobium spp. but also by colonization of their roots by arbuscular mycorrhiza fungi (Asimi et al, 1980;Bayne & Bethlenfalvay, 1987) which are present in the Guinea Savanna soils (Ahiabor, unpublished work). Unfortunately, the full potentials of these management practices on cereal yield improvement are not achieved since the grain legumes mobilize most of their fixed N into the grain which is exported when the grain is harvested.…”

Section: Introductionmentioning

confidence: 99%

Comparative Nitrogen fixation, native arbuscular mycorrhiza formation and biomass production potentials of some grain legume species grown in the iield in the Guinea Savanna Zone of Ghana

Ahiabor¹,

Fosu²,

Tibo³

et al. 2009

West African Journal of Applied Ecology

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An on-station trial was conducted in the experimental field of Savanna Agricultural Research Institute at Nyankpala in the Northern Region of Ghana to assess the nitrogen fixation, native arbuscular mycorrhizal formation and biomass production potentials of cowpea (Vigna unguiculata), devil-bean (Crotalaria retusa), Mucuna pruriens var. utilis (black and white types) and Canavalia ensiformis with maize (Dorke SR) as the reference crop using the total nitrogen difference (TND) method. Plants were fertilized with 40 kg P/ha and 30 kg K/ha at 2 weeks after planting and grown for 55 days after which they were harvested. The harvested biomass (separated into roots, stems and leaves) of each crop was oven-dried at 70 o C for 48 h to a constant weight. Cowpea and devil-bean produced approximately 5 and 6 t/ha biomass whereas Mucuna and Canavalia yielded about 2 t/ha biomass each. Although cowpea had the least number of arbuscular mycorrhiza fungal (AMF) spores in its rhizosphere, its roots were the most heavily colonized (34%) and M. pruriens recording below 5% colonization. Apart from C. ensiformis, the test legumes derived over 50% of their total accumulated N from the atmosphere with cowpea being the most efficient (90% Ndfa). Both N and P accumulations were significantly higher in cowpea than the other legumes due to increased N concentration and dry matter accumulation, respectively. In all the legumes, there was a direct positive correlation between the extent of mycorrhiza formation, biological N fixation and total N uptake. It could, therefore, be concluded that the extensive mycorrhiza formation in cowpea and its high N 2 -fixing potential resulted in a high shoot N and P uptake leading to a comparatively better growth enhancement. Cowpea could, therefore, be the grain legume for consideration in the selection of a suitable legume pre-crop to cereals for the amelioration of the low fertility of the degraded soils of the Guinea savanna zone of Ghana, and also as a source of food to fill the hunger gap that precedes the growing season in the Northern Region of Ghana.

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“…When the availability of P is low, increased P uptake in legumes colonized by VAM2 fungi enhances host plant growth and also stimulates N2 fixation (2,12,14). This has been defined as mycotrophic growth (15).…”

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confidence: 99%

Interactions between Nitrogen Fixation, Mycorrhizal Colonization, and Host-Plant Growth in the Phaseolus-Rhizobium-Glomus Symbiosis

Bethlenfalvay¹,

Pacovsky²,

Bayne³

et al. 1982

Plant Physiol.

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Bean (Phaseolus vulgaris L. cv. Dwarf) roots were inoculated with Rhizobium phaseoli and colonized by the vesicular-arbuscular mycorrhizal (VAM) fungus Glomusfasciculatum Gerd. and Trappe or left uncolonized as controls. The symbiotic associations were grown in an inert substrate using 0, 25, 50, 100, or 200 milligrams hydroxyapatite (HAP) (CaioIPO4161OH12) per pot as a P amendment. Plant and nodule dry weights and nodule activity increased for both VAM and control plants with increasing P availability, but values for VAM plants were significantly lower in all parameters than for controls. Inhibition of growth and of N2 fixation in VAM plants was greatest at the lowest and highest P regimes. It was smallest at 50 milligrams HAP, where available P at harvest (7 weeks after planting) was 5 micrograms P per gram substrate. At this level of P availability, the association apparently benefited from increased P uptake by the fungal endophyte. Percent P values for shoots, roots, and nodules did not differ significantly (p > 0.05) between VAM and control plants. The extent of colonization, fungal biomass, and the fungus/association dry weight ratio increased several fold as HAP was increased from 0 to 200 milligrams. It is concluded that intersymbiont competition for P and photosynthate was the prunary cause for the inhibition of growth, nodulation, and nodule activity in VAM plants. Impaired N2 fixation resulted in N stress which contributed to inhibition of host plant growth at all levels of P availability.Enhancement of N2 fixation by root nodules as a result of improved P nutrition is well documented (12,18,20), and appears to depend on the high P requirement of the bacteriods (3). When the availability of P is low, increased P uptake in legumes colonized by VAM2 fungi enhances host plant growth and also stimulates N2 fixation (2,12,14). This has been defined as mycotrophic growth (15 significant sink for carbohydrates (6). Nodulation and N2 fixation have also been shown to depend directly on the availability of carbohydrates (9). Competition for photosynthates by the microsymbionts of the tripartite legume/Rhizobium/VAM fungal association therefore appears likely.The benefits of enhanced nutrient uptake by VAM fungi may be counteracted by the loss of carbohydrates from the host to the fungal endophyte (21). The concentration of P in the substrate appears to be crucial in determining whether VAM colonization will be beneficial, detrimental, or will occur at all. When P is extremely limiting, growth of both symbionts is inhibited (12). When P availability is low, enhanced growth of the host occurs (mycotrophy; Ref. 15). At intermediate levels of P, fungal proliferation may be at the expense of the host without enhancing P uptake ( 13), while at the high levels of P fungal growth is inhibited (21). In a nonsorbing medium, such as the sand-perlite culture with HAP as the P source used in the present investigation, P concentration at the absorbing root or fungal surface depends on the distance between absorbi...

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Influence of increasing soil phosphorus levels on interactions between vesicular–arbuscular mycorrhizae and Rhizobium in soybeans

Cited by 120 publications

References 0 publications

ACTIVITY OF NITRATE REDUCTASE IN TRIFOLJUMSUBTERRANEUM: EFFECTS OF MYCORRHIZAL INFECTION AND PHOSPHATE NUTRITION

ACTIVITY OF NITRATE REDUCTASE IN TRIFOLJUMSUBTERRANEUM: EFFECTS OF MYCORRHIZAL INFECTION AND PHOSPHATE NUTRITION

Comparative Nitrogen fixation, native arbuscular mycorrhiza formation and biomass production potentials of some grain legume species grown in the iield in the Guinea Savanna Zone of Ghana

Interactions between Nitrogen Fixation, Mycorrhizal Colonization, and Host-Plant Growth in the Phaseolus-Rhizobium-Glomus Symbiosis

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