Submitted to: Mycorrhizae
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/15/2005
Publication Date: 7/1/2005
Citation: Mohammad, M.J., Pan, W.L., Kennedy, A.C. 2005. Chemical alteration of the rhizosphere of the mycorrhizal-colonized wheat root. Mycorrhiza 15:327-332. Interpretive Summary: Wheat plants can be colonized by beneficial fungi called mycorrhizal fungi. These fungi help plants explore more of the soil and increase nutrient uptake by plants. In growth chamber experiments we studied the changes on and near the root (rhizosphere) of wheat colonized by mycorrhizal fungi to determine if the inoculated plant can utilize otherwise unavailable sources of phosphorus and micronutrients. Mycorrhizal inoculation increased root colonization by the fungi. Inoculation of the fungi lowered pH in the rhizosphere, decreased Mn uptake by the plant and increased phosphorus and zinc uptake with inoculation. Certain phosphorus fractions and the phosphorus bioavailability index increased with inoculation, which indicates that mycorrhizal roots were able to utilize unavailable forms of soil phosphorus. This research shows that mycorrhizal fungi can help the plant take up nutrients that would not normally be available to it. These findings can further the use of mycorrhizal fungi to enhance plant growth, especially in low nutrient soils.
Technical Abstract: Growth chamber experiments were conducted to evaluate chemical alterations in the rhizosphere of mycorrhizal wheat roots after inoculation with Glomus intraradices (AMF). Exchange resins were used as sinks for nutrients to determine whether the inoculated plant can utilize the unavailable sources of P and micronutrients. Treatments included: i. Soil (bulk soil); ii. AMF inoculation no P addition (I-P); iii. No inoculation with no P addition (NI-P); iv. AMF inoculation with the addition of 50 mg P kg-1 soil (I+P) and v. No inoculation with the addition of 50 mg P kg-1 soil (NI+P). Spring wheat (Triticum aestivum cv. 'Len') was planted into each plexiglass pot and grown in a growth chamber for two weeks where water was maintained at field capacity. Rhizosphere pH and Eh, nutrient bioavailability indices and mycorrhizal colonization were determined. Mycorrhizal inoculation increased root colonization by the fungi when P was not added. The rhizosphere pH was lower in the inoculated pots compared to the non-inoculated while the Eh did not change. The decrease in pH in the rhizosphere of inoculated plants may have increased P and Zn uptake with inoculation. In contrast, Mn uptake was decreased by inoculation. The resin-adsorbed P was increased by inoculation which, along with the bioavailability index data, may indicate that mycorrhizal roots were able to utilize unavailable forms of soil P.