10 grass species examined. Others reported that drought induced a significant increase in the antioxidant status This study was conducted to determine whether the plant endogein plants (Moran et al., 1994; Mukherjee and Choudhuri, nous antioxidant concentration is responsive to exogenous hormonecontaining products (HCPs) in two turfgrass species subjected to 1983; Smirnoff and Colombe, 1988 ). drought. Two-week-old seedlings of tall fescue (Festuca arundinacea Proper application of certain HCPs not only can im-Schreb.) and creeping bentgrass (Agrostis palustris Huds. A.) were prove turfgrass growth but also can enhance stress tolertreated with two HCPs, seaweed extract (SWE) at 326 g ha Ϫ1 or humic ance (Schott and Walter, 1991; Schmidt and Zhang, acid (HA, 25% a.i.) at 5 L ha Ϫ1 , applied alone or in combination and 1997). Seaweed extract and HA contain organic comgrown under either Ϫ0.03 or Ϫ0.5 MPa soil moisture for 5 wk. Growth pounds that generate auxin-or cytokinin-like activity. and antioxidant status of leaves were determined subsequently. The When these materials are applied to plants, they en-HCP treatments significantly improved leaf water status (LWS) and hance plant tolerance to salinity, drought, chilling, and shoot and root growth of the grasses grown under high (Ϫ0.03 MPa) other environmental stresses; increase antioxidant activand low (Ϫ0.5 MPa) soil moisture. ␣-Tocopherol concentration inity; and improve turfgrass quality (Crouch and Van Stacreased significantly and ascorbic acid concentration remained unchanged for drought-stressed compared with nonstressed turfgrass. den, 1993; Fagbenro and Agboola, 1993;Finnie and Van The HCP treatments significantly increased ␣-tocopherol and ascorbic Staden, 1985;Nabati, 1991;O'Donnell, 1973; Nelson acid concentration of the grasses grown under high and low soil moisand van Staden, 1984; Schmidt and Zhang, 1997; Zhang ture. Positive correlation between antioxidants and shoot or root and Schmidt, 1999).

The purpose of this study was to determine if exogenous hormonecontaining 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 wk, 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 α‐tocopherol, ascorbic acid, and β‐carotene content but did not influence superoxide dismutase (SOD) activity. Foliar application of HCP significantly increased α‐tocopherol, ascorbic acid, β‐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.

No abstract

A variety of organic materials such as humic substances, seaweed extracts (SWE), organic matter, and amino acids are being used as fertilizer supplements in commercial turfgrass management. Among them, SWE and humic acid (HA) are widely used in various biostimulant product formulations. These compounds have been reported to contain phytohormones and osmoprotectants such as cytokinins, auxins, polyamines, and betaines. Manufacturer claims are that these products may supplement standard fertility programs by reducing mineral nutrient requirements while improving stress tolerance. There is a lack of season-long, field-based evidence to support these claims. This study was conducted to investigate the influence of monthly field applications of SWE, HA, and high and low seasonal fertilization regimes on the physiological health of fairway-height creeping bentgrass (Agrostis stolonifera L.). Plots were treated monthly with SWE at 16 mg·m-2 and HA (70% a.i.) at 38 mg·m-2 alone, or in combination, and were grown under low (20 kg·ha-1/month) or high nitrogen (50 kg·ha-1/month) fertilization regimes during 1996 and 1997. Endogenous antioxidant superoxide dismutase (SOD) activity, photochemical activity (PA), and turf quality were measured in July of each year. Superoxide dismutase activity was increased by 46% to 181%, accompanied by a PA increase of 9% to 18%, and improved visual quality of bentgrass in both years. There was no significant fertilization × supplement interaction. Although not part of our original objectives, it was noted that significantly less dollar spot (Sclerotinia homoeocarpa F.T. Bennett) disease incidence occurred in supplement-treated bentgrass. Our results indicate that increased SOD activity in July due to SWE and/or HA applications improved overall physiological health, irrespective of fertilization regime. This suggests that these compounds may be beneficial supplements for reducing standard fertilizer and fungicide inputs, while maintaining adequate creeping bentgrass health.

Seaweed (Ascophyllum nodosum) is a known source of plant growth regulators, and application to turfgrasses has increased activity of the antioxidant superoxide dismutase (SOD) and specific vitamin precursors. Increased antioxidant activity in both plants and animals diminishes oxidative stress. Two pasture experiments investigated effects of Tasco-Forage (a proprietary seaweed-based product) applied to tall fescue (Festuca arundinacea) on antioxidant activity in plants and in ruminants that grazed the forage. In Exp. 1, fescue was 70 to 100% infected with the endophyte fungus Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). Twenty-four wether lambs (initial BW 41 kg; SD = 5) grazed fescue treated with 0, 1.7, or 3.4 kg Tasco/ha applied in April and July, 1994, with four replications per treatment. Grazing occurred for 26 d beginning April 21 and for 22 d beginning July 19. In July, there was a linear increase in daily gains (P < 0.05), and serum vitamin A (P < 0.13) and whole-blood Se (P < 0.10) tended to increase in lambs grazing Tasco-treated fescue. In Exp. 2,48 Angus and Angus x Hereford steers (initial BW 245 kg; SD = 20) grazed infected or uninfected tall fescue in Virginia that was treated (3.4 kg/ ha) or untreated with Tasco in April and July, 1995. Steers that grazed infected tall fescue had lower (P < 0.02) serum vitamin A and E and tended (P < 0.07) to have lower whole-blood Se in September compared with steers that grazed uninfected tall fescue. Tasco decreased (P < 0.06) serum vitamin E but tended to increase whole-blood Se (P < 0.10) in September and serum vitamin A in July (P < 0.12). During 1996 and 1997, the experiment was repeated in Virginia with Angus steers and was replicated at Prairie, MS, where 1/4 Brahman x 3/4 Angus steers were used. Forty-eight steers were included at each location in each year (n = 192 total steers for 1996 and 1997). Steers that grazed infected tall fescue in Mississippi had lower (P < 0.05) serum vitamin E by the end of the grazing season. At both locations Tasco increased (P < 0.05) activity of superoxide dismutase in both infected and uninfected fescue. The endophyte in tall fescue seemed to decrease antioxidant activity in grazing steers, whereas Tasco seemed to increase antioxidant activity in both the forage and the grazing ruminant. Tasco may provide opportunities to reduce oxidative stress in plants and animals.