Interactive Effects of Mycorrhization and Fertilization on Growth, Nutrition, and Water Relations of Sweet Birch

Abstract

Pisolithus tinctorius(Pers.) Coker & Couch was evaluated as an ectomycorrhizal associate of sweet birch (Betula lentaL.). Sand culture and mine soil growth media were employed, and three fertilization treatments were imposed by application of differing Hoagland's nutrient solution #2 concentrations. The high fertilization treatment suppressed mycorrhizal formation by P. tinctoriusin both growth media, while the medium rather than the low treatment induced the most extensive colonization by this mycobiont. Seedlings with induced P. tinctoriusmycorrhization exhibited enhanced above— and below-ground growth according to shoot dimensions and dry weight and root weight and length. However, these responses were frequently absent with high fertilization, especially in the mine soil. Inoculated seedlings had higher foliar N, P, and K concentrations overall but lower Ca, Mg, and S concentrations than uninoculated seedlings. Those with P. tinctoriusalso had lower concentrations of several potentially phytotoxic trace elements, specifically Zn, B, Mo, and Al. Furthermore, xylem pressure and soil water potentials measured during a simulated drought episode indicated that water uptake was enhanced by these mycorrhizae. Again, however, the above physiological responses were often compromised by high fertilization. Collectively, these results indicate that P. tinctoriusis a viable mycobiont for the inoculation of sweet birch, and when substrate fertility is not excessive, can avail this host of physiological benefits that result in substantial growth enhancement.