SUMMARYFive potting media components mixed in various combinations and in various percentages of one with another (0, 14·3, 29, 42, 57, 71 and 100% by volume of the second component with the first) were inoculated with Glomus intraradix in six experiments. Seedlings of citrus rootstocks were grown from seed in these mixes. Sour orange in inoculated peat plus vermiculite, Astatula fine sand plus vermiculite, and peat plus Perlite® in all percentage combinations grew c. two- to threefold taller than noninoculated control plants. Up to twofold growth increases of sour orange occurred in vermiculite amended with wood shavings. The best evidence for fungus-mediated plant growth occurred in Astatula fine sand amended with 29–71% Perlite, and the roots in that combination had the highest percentage of infection. In another experiment in which Astatula fine sand was amended with up to 16% of an acid peat, ratios of inoculated rough lemon plant growth to controls decreased as the peat content in the medium increased. Top and root weight ratios of inoculated:control seedlings in the six experiments did not fit four simple linear models.
A Vesicular Arbuscular Mycorrhizal Fungus (Glomus intraradix) Induces a Defense Response in Alfalfa Roots
