Thursday, November 8, 2007 - 10:00 AM

Auxin-Boosted Biosolids Impact Leaf and Root Hormones Associated with Drought Resistance in Tall Fescue.

Erik H. Ervin1, Xunzhong Zhang2, Gregory Evanylo1, and Katie Haering2. (1) Virginia Tech, CSES Department, 335 Smyth Hall, Blacksburg, VA 24061, (2) CSES Department, Virginia Tech, Blacksburg, VA 24061-0404

Biosolids are increasing in their use as soil amendments, however, the physiological mechanisms of the biosolids' impact on plant growth and stress resistance are not clear. This study was conducted to investigate hormonal (cytokinin, abscisic acid, and auxin) changes as influenced by auxin-boosted biosolids during progressive dry down cycles. Auxin-boosted biosolids, non-auxin-boosted biosolids, and indole-3-butyric acid (IBA) were applied to tall fescue seedlings at an equivalent auxin rate (1.7µM) via soil-drench.  The results indicated that auxin boosted biosolids enhanced turf-type tall fescue performance under well-watered and drought stressed conditions. Both auxin-boosted biosolids and IBA treatments had similar effects in delaying leaf wilting under drought stress. Auxin-boosted biosolids significantly increased root mass under well-watered and drought stress regimes, when compared to the control and non auxin-boosted biosolids.  Auxin-boosted biosolids treatment also enhanced cytokinin content, superoxide dismutase activity, and proline content in leaf tissue compared to the control.  Enhancement of drought resistance by auxin-boosted biosolids may be associated with a shift of hormonal balance, which initiates plant defense responses in the early stages of stress and metabolically regulates turfgrass stress resistance and performance.