Indigenous arbuscular mycorrhizal (AM) fungi contribute to wheat phosphate uptake in a semi-arid field environment, shown by tracking with radioactive phosphorus (original) (raw)
Related papers
Mycorrhizal Fungi Can Dominate Phosphate Supply to Plants Irrespective of Growth Responses1
2003
Arbuscular mycorrhizal (AM) fungi are vital components of nearly all terrestrial ecosystems, forming mutually beneficial (mutualistic) symbioses with the roots of around 80% of vascular plants and often increasing phosphate (P) uptake and growth. We present novel data showing that AM fungi can provide the dominant route for plant P supply, even when overall growth or P uptake remains unaffected. The results will change our understanding of the roles of AM fungi in agricultural and natural ecosystems; they also predict that mycorrhiza-specific plant P transporters must play a major role in plant P uptake regardless of whether the plants respond to AM colonization by taking up more P per plant or by increased dry weight, compared with nonmycorrhizal (NM) control plants.
2014
In the southern Australian cropping zone, large areas of land contain legume-based pastures; these provide feed for livestock and nitrogen for following crops. Annual pastures, especially of Trifolium subterraneum (subterranean clover), are widely sown in Mediterranean climates around the globe and particularly in southern Australia. However, the predominance of annual pastures and crops in south-western Australia has caused problems, including dryland salinisation. Consequently, the development of novel perennial pasture plants, including Australian natives, has been a research priority over the past 15 years. Phosphorus fertiliser is a common input to farms in southern Australia and its use has much increased soil P concentrations. However, rock phosphate is a non-renewable resource and it is now more important to use it efficiently. Forming a symbiosis with arbuscular mycorrhizal fungi (AMF) is an important means for plants to enhance their P uptake, primarily because their exter...
Plant and Soil, 2005
Diversity in phosphorus (P) acquisition strategies was assessed among eight isolates of arbuscular mycorrhizal fungi (AMF) belonging to three Glomus species, all obtained from the same field site. Maize (Zea mays L. cv. Corso) was used as a test plant. Compartmented cultivation containers coupled with 33 P radioisotope labeling of soil P were employed to estimate (1) the distance from the roots that AMF were able to acquire soil P from, (2) the rate of soil colonization, (3) the efficiency of uptake of soil P by AMF, (4) benefits provided to maize in terms of P acquisition and growth. Glomus mosseae and G. intraradices took up P 10 cm from roots, whereas G. claroideum only up to 6 cm from the roots. G. mosseae most rapidly colonized the available soil volume and transported significant amounts of P to maize from a distance, but provided no net P uptake benefit to the plants. On the other hand, both G. intraradices and three out of four G. claroideum isolates significantly improved net P uptake by maize. These effects seem to be related to variability between and to a limited extent also within AMF species, in mycelium development, efficiency of hyphal P uptake and effects on plant P acquisition via the root pathway. In spite of absence of maize growth responses to inoculation with any of the AMF isolates, this study indicates remarkable functional diversity in the underground component of the studied field site.
Plant and Soil, 2004
The double compartment technique has been commonly used in studies on nutrient uptake by mycorrhizas whereas the double pot technique has been used to assess the nutritional stress of plants grown in different soils. A combination of the double pot and the double compartment technique was used as a tool to understand the processes involving mycorrhiza and plant nutrition. Maize (Zea mays) and three species of the arbuscular mycorrhizal fungi in the genus Glomus were used to study phosphorus (P) uptake with and without mycorrhiza from the A and B horizons of an Oxisol. The plants were supplied from the lower pot with a nutrient solution without P. The upper pot had a double compartment with either a fine and coarse mesh screen to control the volume of soil explored by the roots, and thereby, limit the amount of soil P accessible to plants from the test soil. There were significant effects of time for plants grown in both soil horizons, and of mycorrhizas for plants grown in the A soil horizon. No effect of mesh size was observed. There were significant effects of horizon and mycorrhiza, but not of mesh size, on the dry weight and P contents of shoots and roots. The P concentration (P g kg −1 of plant) for shoots and roots was similar in the A and B soil horizons. The results showed that the double pot -double compartment system was suitable for the experimental objectives. No differences in plant growth were observed when root growth was not limited vs root growth limited to the inner compartment because the non-mycorrhizal plants did not take up P. Consequently, responsiveness of the maize cultivar was wholly dependent on mycorrhiza for P uptake under these experimental conditions.
Forest Ecology and Management, 2007
The potential benefits of inoculation with AM (arbuscular mycorrhizal) fungi were investigated on Atlas Cypress (Cupressus atlantica G.), an endemic Cupressacea in Morocco. The parameters under study were (i) the growth of the plant, (ii) the functional diversity of soil microflora and (iii) the rock phosphate (RP) solubilizing activity. C. atlantica growth was measured after 12 months of culture in plastic bags arranged in a randomised complete block design with 10 replicates per treatment. Fungal inoculation consisted of either Glomus intraradices alone or a mixture of native AM fungi. P amendment was supplied under the form of Khouribga Rock Phosphate (KRP) powder. Microbial catabolic diversity was assessed by measuring CO 2 production of SIR (substrate induced respiration) responses. Results showed that: (i) the fungal symbionts were effective to improve the growth of C. atlantica, confirming the requirement of mycorrhizal symbiosis for the successful establishment of C. atlantica in a degraded soil; (ii) G. intraradices appeared to be the most effective in promoting growth of C. atlantica, whereas indigenous AM fungi were relatively ineffective. Native AM fungi inoculation strongly modified functional abilities of the soil microflora, and in the treatments with P amendment, growth stimulations of native AM fungi inoculation were significantly higher than those of G. intraradices inoculation for the shoot growth and leaf P content; (iii) C. atlantica plants inoculated with native AM fungi could mobilize P from KRP more efficiently than those mycorrhized with G. intraradices. A strong interaction between KRP amendment and fungus inoculation was detected for the leaf P content results. In conclusion, the use of a mixture of native AM fungi combination may increase the chance of including one very effective fungal isolate, but also, creates a more favourable environment for the development of ecosystems processes. #
Carbon flow from plant to arbuscular mycorrhizal fungi is reduced under phosphorus fertilization
Plant and Soil, 2017
Background and aims Arbuscular mycorrhizal fungi (AMF) are plant root symbionts highly specialized upon phosphorus (P) supply to their hosts. We investigated plants' ability to regulate carbon (C) flow to AMF depending on the soil P supply. Methods Leek (Allium porrum), medic (Medicago truncatula), and ryegrass (Lolium perenne) were subjected to AMF inoculation and/or P fertilization in a glasshouse experiment. The C flows were traced using 13 C pulse labelling. Results Mycorrhizal P uptake responses were lowered by P fertilization in all tested plant species. Independently from the C flow to the roots, the C flow to AMF-signature fatty acid 16:1ω5 were reduced by P fertilization in leek and ryegrass (but not in medic). Calculated mycorrhizal C costs ranged between 0.9% and 10.5% of the plant C budget. Conclusions Suppression of the C flow from the plants to AMF resulted from both reduced abundance of AMF in the roots and lowered relative C income per unit of AMF biomass in P-fertilized pots. Although inconsistencies amongst different plant species demand caution in making generalizations, these results suggest an active role of host plants in regulating the C flow to AMF.
Plant and Soil, 2012
Field studies have indicated that plantavailable P supply is the main determinant of the performance of arbuscular mycorrhiza (AM) of crops. Direct evidence is, however, weak. Our aim was to test the hypothesis that plant-available P is the main factor determining the benefit from AM to plant P uptake and growth in contrasting cropping systems. We compared a conventional system with full and half fertilisation rates and a low-input system with and without composting of residues. After 15 years, plant P response functions, with and without AM, were determined in a bioassay. At equal plant availability of P, the benefits from AM were similar to those at the P status in the field: The benefits were greater in the low-input system than in the conventional system, irrespective of the fertilisation rate but clearest with composting. This shows that differences between the systems in the benefit from AM to a particular crop genotype are not mainly due to differences in plantavailable P. The results suggest also that differences in P pools, in growth-limiting factors such as N supply and in phytotoxicity to AMF hyphae play roles in determining the benefit. It is not likely that differences in AMF communities are important.
Frontiers in Plant Science, 2021
Phosphorus (P) availability is usually low in soils around the globe. Most soils have a deficiency of available P; if they are not fertilized, they will not be able to satisfy the P requirement of plants. P fertilization is generally recommended to manage soil P deficiency; however, the low efficacy of P fertilizers in acidic and in calcareous soils restricts P availability. Moreover, the overuse of P fertilizers is a cause of significant environmental concerns. However, the use of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB), and the addition of silicon (Si) are effective and economical ways to improve the availability and efficacy of P. In this review the contributions of Si, PSB, and AMF in improving the P availability is discussed. Based on what is known about them, the combined strategy of using Si along with AMF and PSB may be highly useful in improving the P availability and as a result, its uptake by plants compared to using either of them alone. A better understanding how the two microorganism groups and Si interact is crucial to preserving soil fertility and improving the economic and environmental sustainability of crop production in P deficient soils. This review summarizes and discusses the current knowledge concerning the interactions among AMF, PSB, and Si in enhancing P availability and its uptake by plants in sustainable agriculture.
Aims We investigated the role of arbuscular mycorrhizal fungi (AMF) and heterotrophic soil microbes in the uptake of phosphorus (P) by Trifolium subterraneum from a pulse. Methods Plants were grown in sterilised pasture field soil with a realistic level of available P. There were five treatments, two of which involved AMF: 1) unsterilised field soil containing a community of AMF and heterotrophic organisms; 2) Scutellospora calospora inoculum (AMF); 3) microbes added as filtrate from the field soil; 4) microbes added as filtrate from the S. calospora inoculum; 5) no additions, i.e. sterilised field soil. After 11 weeks, plants were harvested: 1 day before (day 0), 1 day after (day 2) and 7 days after (day 8) the pulse of P (10 mg kg −1 ). Results There was no difference among treatments in shoot and root dry weight, which increased from day 0 to day 8. At day 0, shoots and roots of plants in the colonised treatments had higher P and lower Mn concentrations. After the pulse, the rate of increase in P concentration in the shoots was slower for the colonised plants, and the root Mn concentration declined by up to 50 % by day 2. Conclusions Plants colonised by AMF had a lower rate of increase in shoot P concentration after a pulse, perhaps because intraradical hyphae accumulated P and thus reduced its transport to the shoots.
Phosphorus threshold for arbuscular mycorrhizal colonization of crops and tree seedlings
The study was conducted to investigate the effect of phosphorus (P) concentrations (0, 5, 10, 20, 50, and 100 μg g−1) on growth and arbuscular mycorrhizal (AM) colonization of two crops (a rainy season crop, Phaseolus mungo Roxb. var. PU-35 and a winter crop, Triticum aestivum L. var. WH-147) and seedlings of two multipurpose tree species (Eucalyptus tereticornis Sm. [Clone C-7, ITC, Bhadrachalam] and Albizia procera Benth.). Plant growth parameters (shoot length, dry weight) and P uptake increased significantly after inoculations with AM fungi (Acaulospora scrobiculata Trappe, Glomus cerebriforme McGee, and Glomus intraradices Schenck and Smith) in P. mungo, T. aestivum, E. tereticornis, and A. procera. Best results were obtained with G. cerebriforme in P. mungo and A. procera, and A. scrobiculata in T. aestivum, and G. intraradices in E. tereticornis. Results on effect of P application on mycorrhizal dependency (MD) of studied crop and tree species showed that decrease in MD with increase in P concentrations in non-nitrogen-fixing species (T. aestivum and E. tereticornis) was higher than in nitrogen-fixing species (P. mungo and A. procera). Threshold P concentrations for maximum benefits from the AM symbiosis in above-mentioned plant species varied from 5 to 20 μg g−1 and corresponding peaks of arbuscules, vesicles, sporocarp formation, colonization index, and spore count per 100 g sand were noticed. Thus, the results showed that the recorded plant growth peaks were due to AM colonization of crops and tree rhizosphere. Inoculations with AMF were more important than P application (explaining 14–78% variation in plant growth) for P. mungo, T. aestivum, and A. procera (forward selection method), whereas P application was more important for growth in E. tereticornis. Therefore, inoculating plants with a suitable AM inoculant could result in a benefit comparable to high P input and lead to a significant saving of inorganic P fertilizer.