BORIC-ACID PHENOLIC RELATIONSHIPS WITHIN THE PINUS-ECHINATA PISOLITHUS-TINCTORIUS ECTOMYCORRHIZAL ASSOCIATION

At germination, container-grown shortleaf pine seedlings were inoculat ed with Pisolithus tinctorius (Pers.) Coker & Couch or left uninoculat ed, and both groups were fertilized semiweekly with a modified Hoaglan d's solution supplemented with 0 or 0.4 mM boric acid. After 12, 16 an d 24 weeks, seedling root tissue was analyzed for ectomycorrhizal colo nization, phenolic concentration and phenoloxidase activity. In additi on, phenoloxidase activity was assayed in P. tinctorius that had been cultured in a liquid medium containing boric acid. Inoculation with P. tinctorius increased the root phenolic concentration of 16- and 24-we ek-old seedlings, and increased root phenoloxidase activity in 12-, 16 - and 24-week-old seedlings. Fertilization with boric acid reduced the phenolic concentration of P. tinctorius ectomycorrhizae after 24 week s. Although boric acid fertilization did not affect the phenoloxidase activity of 12-, 16- and 24-week-old inoculated roots, or that of 16- and 24-week-old uninoculated roots, it increased the phenoloxidase act ivity of P. tinctorius grown in vitro and 12-week-old uninoculated roo ts. We conclude that boric acid fertilization influences the phenolic relations of the shortleaf pine-p. tinctorius ectomycorrhizal associat ion, possibly through a boric acid-induced increase in phenoloxidase a ctivity.