Influence of Drought Stress and Mycorrhizae on Growth of Two Native Forbs

Abstract

Seedlings of Baptisia australis (L.) R. Br. and Liatris aspera Michx., grown in prairie soil with no additional P, benefited significantly from inoculation with Glomus etunicatum Becker and Gerd., regardless of whether they were adequately watered or moderately or severely drought-stressed. In the presence of additional P, growth of severely droughted inoculated seedlings for both plant species was not significantly greater than noninoculated plants. When the influence of four Glomus species on growth of the two forbs was compared under drought-stress conditions with no supplemental P, growth of both plant species was signficantly improved by all fungal species compared to noninoculated controls. Preinoculated seedlings of both plant species were transplanted into disturbed-site soils with indigenous vesicular-arbuscular mycorrhizal (VAM) fungi present and subjected to severe moisture stress. After 12 weeks, inoculated seedlings were significantly larger than noninoculated seedlings for all soil types, with or without additional fertilizer (0.15 kg P/m 3 + 0.075 kg N/m 3 ). Under conditions of drought stress and low fertility, preinoculated seedlings of both B. australis and L. aspera grew significantly larger than noninoculated seedlings.