Influence of Mycorrhizae on the Growth of Loblolly Pine Seedlings Exposed to Ozone and Sulfur Dioxide

Abstract

Loblolly pine seedlings, with and without ectomycorrhizae [Pisolithus tinctorius] were exposed to ozone (O3) at 0.07 .mu.l l and sulfur dioxide (SO2) at 0.06 .mu.l/l, singly and in combination, 6 h/day for 5 wk. Exposure to either pollutant alone neither affected mycorrhizal formation nor changed reducing sugar concentrations in the roots. Root growth of nonmycorrhizal seedlings was more severely inhibited by each fumigation treatment than was shoot growth and the root:shoot ratio in these seedlings was lower than that of unfumigated seedlings. Mycorrhizae altered the pollutant effects on root and shoot growth and promoted root growth so that no pollution treatment effects were evident. Fumigated mycorrhizal seedlings had a higher root:shoot ratio compared to unfumigated mycorrhizal seedlings.