Antioxidant response to hormone-containing product in Kentucky bluegrass subjected to drought

The purpose of this study was to determine if exogenous hormone-containing products (HCP) (seaweed extract and humic acid) enhance endogenous antioxidant concentration in Kentucky bluegrass (Poa pratensis L,.) subjected to drought. Two week old seedlings of Kentucky bluegrass (cv. Plush) were treated with seaweed extract at 326 g ha(-1), humic acid (25% active) at 5 L ha(-1), alone or in combination, and grown under two soil moisture levels (-0.03 MPa and -0.5 MPa) for 5,vk, and subsequently analyzed for antioxidant concentration and growth. The HCP treatments improved leaf water status and enhanced shoot and root growth regardless of soil moisture levels. Water stress induced a significant increase of alpha-tocopherol, ascorbic acid, and beta-carotene content but did not influence superoxide dismutase (SOD) activity. Foliar application of HCP significantly increased alpha-tocopherol, ascorbic acid, beta-carotene content, and SOD activity, especially under low soil moisture (LSM). Positive correlations between antioxidants and antioxidants with growth parameters were observed in Kentucky bluegrass grown under either LSM or high soil moisture (HSM). These data indicate that HCP enhancement of the grass's endogenous antioxidant status may contribute to turfgrass drought tolerance.