VESICULAR-ARBUSCULAR MYCORRHIZAL INFECTION EFFECTS ON GROWTH AND UPTAKE OF PHOSPHORUS AND MINERAL ELEMENTS BY SORGHUM (GLOMUS, ALUMINUM).

摘要

The effects of vesicular-arbuscular mycorrhizae (VAM) on sorghum Sorghum bicolor (L.) Moench plant growth and mineral element uptake were studied in soils with different P levels, pH values, and temperatures. Sorghum genotypes were grown with viable and nonviable Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe, Glomus deserticolum Trappe, Bloss, and Menge, and Glomus macrocarpum Tul. and Tul. inocula on steam pasteurized Sharpsburg (fine, montmorillonitic, mesic Typic Argiudolls), Cecil (clayey, kaolinitic, thermic Typic Hapludults), and Burchard (fine-loamy, mixed, mesic Typic Argiudolls) soils under controlled environmental conditions.;Sorghum plants infected with VAM absorbed greater amounts of P, N, K, Mg, S, Ca, Mn, Fe, Cu, and Zn than uninfected plants when grown on a low P soil. The greater uptake of P was attributed to a larger absorption surface area offered by longer roots and to VAM hyphae external to roots. Phosphorus-efficient and P-inefficient sorghum genotypes showed larger relative differences in plant growth and mineral element uptake in the absence of VAM infection than in the presence of infection.;Infection with G. fasciculatum or addition of 12.5 mg P kg('-1) (equivalent to 25 kg P ha('-1)-15 cm) resulted in similar sorghum shoot dry matter increments on a low P soil. Analyses of benefits derived from VAM and costs paid by plants for these associations may be useful in the selection of sorghum genotypes and VAM fungi species for different soil conditions.;Sorghum plant growth and P uptake were enhanced most at soil pH 4.49 and depressed at soil pH 4.13 and 5.77 by infection with G. deserticolum. Available soil P and Al levels may be critical for sorghum root infection with VAM and VAM fungi activity.;A VAM inoculum placed intact as a core 2 cm below seeds at planting gave higher sorghum root infection than the same amount of inoculum dispersed through soil. A gridline intersect method measured percentage root infection with VAM more precisely than a visual method.;Sorghum plant growth and mineral element uptake were enhanced considerably more by G. macrocarpum than G. fasciculatum and G. deserticolum at the temperature range of 20 to 30(DEGREES)C. Sorghum plant growth responses to G. macrocarpum were lowest at 20(DEGREES)C and highest at 25(DEGREES)C.