Mean response of Pinus muricata root length to mycorrhizal colonization. Mean response of P. muricata root length to mycorrhizal colonization (log response ratio = ln(X
) where X
is the root length of inoculated plants and X
is the root length of non-inoculated plants), as influenced by a three-way interaction between P. muricata maternal seed family, soil type (lab versus field), and the addition of a microbial filtrate. Means with different letters are significantly different from each other (p < 0.05) according to Tukey HSD post-hoc tests, and means with an asterisk are significantly different from zero.