The effect of seaweed (Ascophyllum nodosum) extract on antioxidant activities and drought tolerance of tall fescue (Festuca arundinacea schreb.)
Ayad, Jamal Yousef
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Plants have developed enzymatic and nonenzymatic antioxidant mechanisms to prevent oxidation of cellular compartments. Enhancing these mechanisms might help plants cope with encountered stresses. Greenhouse and field studies were conducted to examine the influence of seaweed(Ascophyllum nodosum) extract on antioxidant enzymes activities, forage growth, and persistence of tall fescue (Festuca arundinacea Schreb.). Furthermore, effects of soil moisture, plant genotype, and infection with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon and Hanlin) were investigated. In a greenhouse experiment, seaweed extract was applied to 'Martin' tall fescue at 0, 2, 4, 6, 8, and 10 kg ha^-1 in a randomized block design with four replicates. Seaweed extract linearly increased (P <0.05) glutathione reductase activity. Superoxide dismutase and ascorbate peroxidase were also increased but responses differed by time and treatment rates. In a second greenhouse experiment, seaweed extract was applied at 4 kg ha^-1 to endophyte-infected and non-infected 'Georgia Jessup' and 'KY-3r tall fescue grown with 50-100% and 30-100% field capacity soil moisture in a completely randomized design with four replications. Glutathione reductase activity increased (P < 0.05) in both genotypes in response to seaweed extract and moisture stress and tended to increase (P < 0.07) in response to the endophyte. Seaweed extract increased (P < 0.05) superoxide dismutase activity in both genotypes under water stress. Endophyte infected and non-infected KY-31 tall fescue were grown in a 2-yr field experiment, to investigate effects of 4 kg seaweed ha^-1 and three levels of irrigation to replace 0, 50,100% of potential evapotranspiration in a randomized block design with four replications. Superoxide dismutase, glutathione reductase, and ascorbate peroxidase activities were increased (P < 0.05) in response to seaweed extract, presence of the endophyte, and increased linearly (P < 0.05) in response to increased moisture stress. Plant growth and yield did not appear to be affected by seaweed extract at the applied rates. Results indicated that seaweed extract increased tall fescue antioxidant enzyme activities and may provide a tool for manipulating the antioxidant system in plants for increased protection against active oxygen species.