Metabolic differences in Zea-Glomus-Azospirillum symbioses

Abstract

Zea mays L. (cv. Early Sunglow) plants were inoculated with either the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus etunicatum, with a strain of Azospirillum brasilense, or with both endophytes together. All plants were grown in a relatively fertile, peat-based potting mix to minimize differences in macronutrient assimilation between treatments. In addition, non-inoculated maize plants were fertilized with amounts of N and P that had been found to compensate for the input of nutrients following colonization by Azospirillum or Glomus. In general, maize plants colonized by Glomus contained more Zn and Cu, but less P, starch, proline, threonine and alanine than corresponding P-fertilized plants. Corn plants colonized by Azospirillum contained less N, soluble sugars, soluble protein, leucine and isoleucine. but more leaf area and glutamate than corresponding N-fertilized plants. Roots of mycorrhizal plants contained a number of lipids [fatty acids 16:1(11 c), 18:3 (6,9,12), 20:3, 20:4 and 20:5] not found in P-fertilized controls. The physiology of the plants inoculated with G. etunicatum or A. brasilense was altered in a manner independent of host mineral status.